From patchwork Thu Feb 6 11:38:03 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Brown X-Patchwork-Id: 13962929 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CAEB8228CA2; Thu, 6 Feb 2025 11:40:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738842018; cv=none; b=MXVLdaEazqeDxSihJ3bvc6XWWD/VQnh61YmB1p1Xp47CW5UirktG0UG6s7k1tiX5xa4XnhNTJl8o8V7GZDdkNH2WOs77JXDHP4/+oMqGfXmypuTaPQbpIBfpqZG61npcw2gb4g194nb/a3nW5gSHG9bHrNoMhYyLSVXQC2Cz/gM= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738842018; c=relaxed/simple; bh=DlNOYnxspap0qJgmVc/Gm5yAn5fxbHqq9onb8IXtjac=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=YtVUtHaV7xbsbM9VlH93wCv8AM30+ZRHHqXaFDFhTAFb8tnw+6hcLg7+9nFArujT/voisSCUp8sPljr01890/WYMZcLavVY3lDbFDxqIgu+S2jzk97buuMzfe9rnwZh9sPuPFdwjO5kYIcd3czUKOQNjbe/fkS1i0Qaox7AzbUc= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Dgxi0nIw; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Dgxi0nIw" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8143EC4CEE6; Thu, 6 Feb 2025 11:40:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1738842017; bh=DlNOYnxspap0qJgmVc/Gm5yAn5fxbHqq9onb8IXtjac=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=Dgxi0nIwDdKrVkQofEEMxMlscerl5Nw6DPXyOwRRJuBy/nDPNnqqQxM0sLclTC9+r gCEEQHDHDwMB6TLNTVFfOySFgDlff1Uwjc4GvW10oEc/ErirLOs9yqBXmBks0WMRVf qbAcPotNiic38h4a/buIfXd3vWXt05qfhRZbm+DmUX0zurLRrhHzp+2D645xdwdmvt iI9N2wAuo+vsMpjaR08Sid90pybFh5AbnmhZa8xR6jsa31dquNZGTTZZOYg2E9Cldq mdoWkje2mn1yKEbpkHQahWX+Xmre+Oe30qC7lO9oHn+PzSS+P+CNz3/X/+XFda0Mcx uLMsvOigN/Lzw== From: Mark Brown Date: Thu, 06 Feb 2025 11:38:03 +0000 Subject: [PATCH RFT v14 1/8] arm64/gcs: Return a success value from gcs_alloc_thread_stack() Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <20250206-clone3-shadow-stack-v14-1-805b53af73b9@kernel.org> References: <20250206-clone3-shadow-stack-v14-0-805b53af73b9@kernel.org> In-Reply-To: <20250206-clone3-shadow-stack-v14-0-805b53af73b9@kernel.org> To: "Rick P. Edgecombe" , Deepak Gupta , Szabolcs Nagy , "H.J. Lu" , Florian Weimer , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Christian Brauner , Shuah Khan Cc: linux-kernel@vger.kernel.org, Catalin Marinas , Will Deacon , jannh@google.com, bsegall@google.com, Yury Khrustalev , Wilco Dijkstra , linux-kselftest@vger.kernel.org, linux-api@vger.kernel.org, Mark Brown , Kees Cook X-Mailer: b4 0.15-dev-1b0d6 X-Developer-Signature: v=1; a=openpgp-sha256; l=3931; i=broonie@kernel.org; h=from:subject:message-id; bh=DlNOYnxspap0qJgmVc/Gm5yAn5fxbHqq9onb8IXtjac=; b=owEBbQGS/pANAwAKASTWi3JdVIfQAcsmYgBnpJ+OQvnyT0+rhQer5acV2/sCH1Pqlw7zB3Ip1695 PKG7w+iJATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCZ6SfjgAKCRAk1otyXVSH0KSKB/ 9sobupBvBfI999rxOHq6tTLahomeXanOvhTzdw4gSh/sB6fuvkKpJMWd+jUR3C6GAiOUjpkKOoLbjE Unywjx8DzIxE/UGAzt1muyCgt2SeMLtQq5PK3QMxGWjxpcC0/jeePol5GGMrnrJVfR9tgJH5SF2g9M 5+GORuAedV51e40Wi0l3Hv+irACfpR+CLYRmS6g8bGBT079TuXunFUjDKjozJNr75JFNXSmkearAgi VmOw9VCDWV2fUtespMpnhfHBGa8xJt2BTxjyEYfAlh+IS6K7zn/eUMws8Tw26mUg/oxM7/56+AThUF yGcTqpY4DvMWMkYctHTNTX0ix7zGlf X-Developer-Key: i=broonie@kernel.org; a=openpgp; fpr=3F2568AAC26998F9E813A1C5C3F436CA30F5D8EB Currently as a result of templating from x86 code gcs_alloc_thread_stack() returns a pointer as an unsigned int however on arm64 we don't actually use this pointer value as anything other than a pass/fail flag. Simplify the interface to just return an int with 0 on success and a negative error code on failure. Acked-by: Deepak Gupta Reviewed-by: Catalin Marinas Signed-off-by: Mark Brown --- arch/arm64/include/asm/gcs.h | 8 ++++---- arch/arm64/kernel/process.c | 8 ++++---- arch/arm64/mm/gcs.c | 8 ++++---- 3 files changed, 12 insertions(+), 12 deletions(-) diff --git a/arch/arm64/include/asm/gcs.h b/arch/arm64/include/asm/gcs.h index f50660603ecf5dc09a92740062df3a089b02b219..d8923b5f03b776252aca76ce316ef57399d71fa9 100644 --- a/arch/arm64/include/asm/gcs.h +++ b/arch/arm64/include/asm/gcs.h @@ -64,8 +64,8 @@ static inline bool task_gcs_el0_enabled(struct task_struct *task) void gcs_set_el0_mode(struct task_struct *task); void gcs_free(struct task_struct *task); void gcs_preserve_current_state(void); -unsigned long gcs_alloc_thread_stack(struct task_struct *tsk, - const struct kernel_clone_args *args); +int gcs_alloc_thread_stack(struct task_struct *tsk, + const struct kernel_clone_args *args); static inline int gcs_check_locked(struct task_struct *task, unsigned long new_val) @@ -91,8 +91,8 @@ static inline bool task_gcs_el0_enabled(struct task_struct *task) static inline void gcs_set_el0_mode(struct task_struct *task) { } static inline void gcs_free(struct task_struct *task) { } static inline void gcs_preserve_current_state(void) { } -static inline unsigned long gcs_alloc_thread_stack(struct task_struct *tsk, - const struct kernel_clone_args *args) +static inline int gcs_alloc_thread_stack(struct task_struct *tsk, + const struct kernel_clone_args *args) { return -ENOTSUPP; } diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c index 42faebb7b712328a8bebd25c47b01f09daae3861..45130ea7ea6e8090f09297a32fa71fe86e6532b9 100644 --- a/arch/arm64/kernel/process.c +++ b/arch/arm64/kernel/process.c @@ -297,7 +297,7 @@ static void flush_gcs(void) static int copy_thread_gcs(struct task_struct *p, const struct kernel_clone_args *args) { - unsigned long gcs; + int ret; if (!system_supports_gcs()) return 0; @@ -305,9 +305,9 @@ static int copy_thread_gcs(struct task_struct *p, p->thread.gcs_base = 0; p->thread.gcs_size = 0; - gcs = gcs_alloc_thread_stack(p, args); - if (IS_ERR_VALUE(gcs)) - return PTR_ERR((void *)gcs); + ret = gcs_alloc_thread_stack(p, args); + if (ret != 0) + return ret; p->thread.gcs_el0_mode = current->thread.gcs_el0_mode; p->thread.gcs_el0_locked = current->thread.gcs_el0_locked; diff --git a/arch/arm64/mm/gcs.c b/arch/arm64/mm/gcs.c index 5c46ec527b1cdaa8f52cff445d70ba0f8509d086..1f633a482558b59aac5427963d42b37fce08c8a6 100644 --- a/arch/arm64/mm/gcs.c +++ b/arch/arm64/mm/gcs.c @@ -38,8 +38,8 @@ static unsigned long gcs_size(unsigned long size) return max(PAGE_SIZE, size); } -unsigned long gcs_alloc_thread_stack(struct task_struct *tsk, - const struct kernel_clone_args *args) +int gcs_alloc_thread_stack(struct task_struct *tsk, + const struct kernel_clone_args *args) { unsigned long addr, size; @@ -59,13 +59,13 @@ unsigned long gcs_alloc_thread_stack(struct task_struct *tsk, size = gcs_size(size); addr = alloc_gcs(0, size); if (IS_ERR_VALUE(addr)) - return addr; + return PTR_ERR((void *)addr); tsk->thread.gcs_base = addr; tsk->thread.gcs_size = size; tsk->thread.gcspr_el0 = addr + size - sizeof(u64); - return addr; + return 0; } SYSCALL_DEFINE3(map_shadow_stack, unsigned long, addr, unsigned long, size, unsigned int, flags) From patchwork Thu Feb 6 11:38:04 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Brown X-Patchwork-Id: 13962930 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8E6012288F0; 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dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="OYjZ12M2" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B00B6C4CEE5; Thu, 6 Feb 2025 11:40:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1738842023; bh=Rn1ReQWjHDBrfM29j7eU9MrcuInkiKGzptMD1gkGnC8=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=OYjZ12M2vVnXlnvNew6MKCGPjXsP0osDyTFqH+UWKKapf6D+TYBvpVUwD2xKhgGPC 5kc723OH49/wOHF15YUErXhGv8OoCobEG6JsDtj7xcCSOjEP2VuFd5CqvcwZvAzMCq 6RP5BxSZu5khiim6G1iUs8JATmFpZ4beFQBZWctRBVGgNsmq5BnmwbUx48wizlGAmP bEMBtk8SP53X0bQatX1FF6aY/olEDg1LnY3oW4VhEJwpFbcgJD5lBX26gZmzTFXCJ4 iz4tfe17SZV5xNptaHLvGg+d+JOGa1WtcwKgIpqrMpXIG7gTGg24/oc9xCeGdGPBHc h2WCYVqdOu3og== From: Mark Brown Date: Thu, 06 Feb 2025 11:38:04 +0000 Subject: [PATCH RFT v14 2/8] Documentation: userspace-api: Add shadow stack API documentation Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <20250206-clone3-shadow-stack-v14-2-805b53af73b9@kernel.org> References: <20250206-clone3-shadow-stack-v14-0-805b53af73b9@kernel.org> In-Reply-To: <20250206-clone3-shadow-stack-v14-0-805b53af73b9@kernel.org> To: "Rick P. Edgecombe" , Deepak Gupta , Szabolcs Nagy , "H.J. Lu" , Florian Weimer , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Christian Brauner , Shuah Khan Cc: linux-kernel@vger.kernel.org, Catalin Marinas , Will Deacon , jannh@google.com, bsegall@google.com, Yury Khrustalev , Wilco Dijkstra , linux-kselftest@vger.kernel.org, linux-api@vger.kernel.org, Mark Brown , Kees Cook , Kees Cook , Shuah Khan X-Mailer: b4 0.15-dev-1b0d6 X-Developer-Signature: v=1; a=openpgp-sha256; l=3299; i=broonie@kernel.org; h=from:subject:message-id; bh=Rn1ReQWjHDBrfM29j7eU9MrcuInkiKGzptMD1gkGnC8=; b=owEBbQGS/pANAwAKASTWi3JdVIfQAcsmYgBnpJ+PEnkMA6qzvTp3Vm7rYeeO6o0S/66rzeoFngaU aII9xhyJATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCZ6SfjwAKCRAk1otyXVSH0JPkB/ 44TBdNZRnlayyrQ5r7mRUxn80kuXWVHlrEJbaWm1Fc6JODvTtJPybM+tKxIoJzBDfWnDbDOB9dQoml Et2ZPU1aNH/IO3tTjHAMdu6FRO35KLGT+2XK4dXQ02jQHHkXZd6OI5qphuBwDwQnXiIBVWPJE9YAo0 sLYLXFfbRvit+ieztexzcCGBbiPPVkQWQg+1k4wmds4aRlMOIwhZR4X2tiI66kXvAJwSh38fvDjYsU WqjrDgnK+FOSItmXJEJeCwvGxiCthGx9+zciaqL1wlxpCiDdCu/rGOUiMuHE2heTYhd0L7PzuCWa8c bu3uFB59g2wxDgxnfonLfMYy4CDFdS X-Developer-Key: i=broonie@kernel.org; a=openpgp; fpr=3F2568AAC26998F9E813A1C5C3F436CA30F5D8EB There are a number of architectures with shadow stack features which we are presenting to userspace with as consistent an API as we can (though there are some architecture specifics). Especially given that there are some important considerations for userspace code interacting directly with the feature let's provide some documentation covering the common aspects. Reviewed-by: Catalin Marinas Reviewed-by: Kees Cook Tested-by: Kees Cook Acked-by: Shuah Khan Acked-by: Yury Khrustalev Signed-off-by: Mark Brown Reviewed-by: Deepak Gupta --- Documentation/userspace-api/index.rst | 1 + Documentation/userspace-api/shadow_stack.rst | 44 ++++++++++++++++++++++++++++ 2 files changed, 45 insertions(+) diff --git a/Documentation/userspace-api/index.rst b/Documentation/userspace-api/index.rst index b1395d94b3fd0a7d43a3a9a9afa329d467675ae5..c491f332d289e6333675b6e41ab7d55b7e108829 100644 --- a/Documentation/userspace-api/index.rst +++ b/Documentation/userspace-api/index.rst @@ -60,6 +60,7 @@ Everything else ELF netlink/index + shadow_stack sysfs-platform_profile vduse futex2 diff --git a/Documentation/userspace-api/shadow_stack.rst b/Documentation/userspace-api/shadow_stack.rst new file mode 100644 index 0000000000000000000000000000000000000000..65c665496624c7d9c33dbd8c714b8dc88c2032b3 --- /dev/null +++ b/Documentation/userspace-api/shadow_stack.rst @@ -0,0 +1,44 @@ +.. SPDX-License-Identifier: GPL-2.0 + +============= +Shadow Stacks +============= + +Introduction +============ + +Several architectures have features which provide backward edge +control flow protection through a hardware maintained stack, only +writeable by userspace through very limited operations. This feature +is referred to as shadow stacks on Linux, on x86 it is part of Intel +Control Enforcement Technology (CET), on arm64 it is Guarded Control +Stacks feature (FEAT_GCS) and for RISC-V it is the Zicfiss extension. +It is expected that this feature will normally be managed by the +system dynamic linker and libc in ways broadly transparent to +application code, this document covers interfaces and considerations. + + +Enabling +======== + +Shadow stacks default to disabled when a userspace process is +executed, they can be enabled for the current thread with a syscall: + + - For x86 the ARCH_SHSTK_ENABLE arch_prctl() + - For other architectures the PR_SET_SHADOW_STACK_ENABLE prctl() + +It is expected that this will normally be done by the dynamic linker. +Any new threads created by a thread with shadow stacks enabled will +themselves have shadow stacks enabled. + + +Enablement considerations +========================= + +- Returning from the function that enables shadow stacks without first + disabling them will cause a shadow stack exception. This includes + any syscall wrapper or other library functions, the syscall will need + to be inlined. +- A lock feature allows userspace to prevent disabling of shadow stacks. +- Those that change the stack context like longjmp() or use of ucontext + changes on signal return will need support from libc. From patchwork Thu Feb 6 11:38:05 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Brown X-Patchwork-Id: 13962931 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id F1A9E22B8AA; Thu, 6 Feb 2025 11:40:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738842030; cv=none; b=FQCFKyG+lTnjA9qjFvciv1LLzuu5+fQjy4B2s3BMdaFE8d4pGWc/NuIHBzkUhiEy6jnw75Mkh7Bt2+dGOovtKS95btLkQcxedf0VYRDV/lbR+0JtdecV6CuEWhRpBM40pi2eEdHJv7AclFssJCQcxnfpynLdAK+LPQMwoulvFEQ= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738842030; c=relaxed/simple; bh=fQK5XH8C8GoDpDyxe5Zvny2D7xuRYfaorJvH/8wiZ5g=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=r260TdGMu9Q84EgUszc64IOkwutznf3V9DZroO6geRC2zKGWUiP42oRLTgReHGLLLpEWF6Lynjt/s44c8r2cLifCIAQZ/p6H010P3AooAKxmi8xFobNKPl7BiAFwG604OUK4ZlQGNO7Pf0r75OpWx/E4842YojEjXDTY+uCezvY= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=fGTIayha; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="fGTIayha" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D2C65C4CEE4; Thu, 6 Feb 2025 11:40:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1738842029; bh=fQK5XH8C8GoDpDyxe5Zvny2D7xuRYfaorJvH/8wiZ5g=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=fGTIayhao0+pUbBJdwS0p7TJ6r8RHZzKLUUynu9KhQ4DuuXgR14mpBIvA4rF0aQ3+ /7X8J9Ga/BCsAIJ6ZnBte4uvu4Tc1MivvlZkqwDQGMYL3QDgoQY4uyg1Bh3rE+i968 bMR1fQ+oj08xY6zzJJPEnAXbyQQqIgZqv7Ec0YL7b9CIId41tDAokuKdb/RI7+BVoX Xqd7th5vJiJJxFffwYIeymMa/46ekb0aSHt15gRbL481R9Gd+/K+SyJdPEVgnJKAXW AGfCDiSq940HPXmeGsQYlZlFMJc7RL02KlElWJHRU4mvyvQY+L2pJ+s7rKUkjFjYf7 afopt4ODP5YWQ== From: Mark Brown Date: Thu, 06 Feb 2025 11:38:05 +0000 Subject: [PATCH RFT v14 3/8] selftests: Provide helper header for shadow stack testing Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <20250206-clone3-shadow-stack-v14-3-805b53af73b9@kernel.org> References: <20250206-clone3-shadow-stack-v14-0-805b53af73b9@kernel.org> In-Reply-To: <20250206-clone3-shadow-stack-v14-0-805b53af73b9@kernel.org> To: "Rick P. Edgecombe" , Deepak Gupta , Szabolcs Nagy , "H.J. Lu" , Florian Weimer , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Christian Brauner , Shuah Khan Cc: linux-kernel@vger.kernel.org, Catalin Marinas , Will Deacon , jannh@google.com, bsegall@google.com, Yury Khrustalev , Wilco Dijkstra , linux-kselftest@vger.kernel.org, linux-api@vger.kernel.org, Mark Brown , Kees Cook , Kees Cook , Shuah Khan X-Mailer: b4 0.15-dev-1b0d6 X-Developer-Signature: v=1; a=openpgp-sha256; l=4385; i=broonie@kernel.org; h=from:subject:message-id; bh=fQK5XH8C8GoDpDyxe5Zvny2D7xuRYfaorJvH/8wiZ5g=; b=owEBbQGS/pANAwAKASTWi3JdVIfQAcsmYgBnpJ+QqLzkhMk9wJVDSdypTpZJiYNDyxZAPD2Vu5qu AwrqWl6JATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCZ6SfkAAKCRAk1otyXVSH0Hr0B/ sFYerhT/fkohPBpkFRsLBB6nxSmT55jUny8/5FrB1EobVG42lsu/+69aDl9feDQ24pEiorfMvdT5tD NGnc2iFYCmLyiE/pSQ9kshZCmePKi7s1dYxA1JghItymqNfIhmMrFLhVp2CGj12aXqH14Fipmh8tKS 4dgrdK/u9Axa3WpecRbXWDW1oTg7ZWK6fQJIYL7ycrwy9B6akgLUS8rzbZsRv1WkouGD5hhApBdViQ zogQDGC9RrNydH2WOVjBxi6Otl/pAl4fXfxpk5AlVpfbMydUCE3W1vJt8mJMNqcpuTe+60S7AEMjH4 2tTIssmDuyzKMKmsayTmvbp1MvKMdO X-Developer-Key: i=broonie@kernel.org; a=openpgp; fpr=3F2568AAC26998F9E813A1C5C3F436CA30F5D8EB While almost all users of shadow stacks should be relying on the dynamic linker and libc to enable the feature there are several low level test programs where it is useful to enable without any libc support, allowing testing without full system enablement. This low level testing is helpful during bringup of the support itself, and also in enabling coverage by automated testing without needing all system components in the target root filesystems to have enablement. Provide a header with helpers for this purpose, intended for use only by test programs directly exercising shadow stack interfaces. Reviewed-by: Rick Edgecombe Reviewed-by: Kees Cook Tested-by: Kees Cook Acked-by: Shuah Khan Signed-off-by: Mark Brown --- tools/testing/selftests/ksft_shstk.h | 98 ++++++++++++++++++++++++++++++++++++ 1 file changed, 98 insertions(+) diff --git a/tools/testing/selftests/ksft_shstk.h b/tools/testing/selftests/ksft_shstk.h new file mode 100644 index 0000000000000000000000000000000000000000..fecf91218ea51edd30c220d4d94e5814e2d69c9e --- /dev/null +++ b/tools/testing/selftests/ksft_shstk.h @@ -0,0 +1,98 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * Helpers for shadow stack enablement, this is intended to only be + * used by low level test programs directly exercising interfaces for + * working with shadow stacks. + * + * Copyright (C) 2024 ARM Ltd. + */ + +#ifndef __KSFT_SHSTK_H +#define __KSFT_SHSTK_H + +#include + +/* This is currently only defined for x86 */ +#ifndef SHADOW_STACK_SET_TOKEN +#define SHADOW_STACK_SET_TOKEN (1ULL << 0) +#endif + +static bool shadow_stack_enabled; + +#ifdef __x86_64__ +#define ARCH_SHSTK_ENABLE 0x5001 +#define ARCH_SHSTK_SHSTK (1ULL << 0) + +#define ARCH_PRCTL(arg1, arg2) \ +({ \ + long _ret; \ + register long _num asm("eax") = __NR_arch_prctl; \ + register long _arg1 asm("rdi") = (long)(arg1); \ + register long _arg2 asm("rsi") = (long)(arg2); \ + \ + asm volatile ( \ + "syscall\n" \ + : "=a"(_ret) \ + : "r"(_arg1), "r"(_arg2), \ + "0"(_num) \ + : "rcx", "r11", "memory", "cc" \ + ); \ + _ret; \ +}) + +#define ENABLE_SHADOW_STACK +static __always_inline void enable_shadow_stack(void) +{ + int ret = ARCH_PRCTL(ARCH_SHSTK_ENABLE, ARCH_SHSTK_SHSTK); + if (ret == 0) + shadow_stack_enabled = true; +} + +#endif + +#ifdef __aarch64__ +#define PR_SET_SHADOW_STACK_STATUS 75 +# define PR_SHADOW_STACK_ENABLE (1UL << 0) + +#define my_syscall2(num, arg1, arg2) \ +({ \ + register long _num __asm__ ("x8") = (num); \ + register long _arg1 __asm__ ("x0") = (long)(arg1); \ + register long _arg2 __asm__ ("x1") = (long)(arg2); \ + register long _arg3 __asm__ ("x2") = 0; \ + register long _arg4 __asm__ ("x3") = 0; \ + register long _arg5 __asm__ ("x4") = 0; \ + \ + __asm__ volatile ( \ + "svc #0\n" \ + : "=r"(_arg1) \ + : "r"(_arg1), "r"(_arg2), \ + "r"(_arg3), "r"(_arg4), \ + "r"(_arg5), "r"(_num) \ + : "memory", "cc" \ + ); \ + _arg1; \ +}) + +#define ENABLE_SHADOW_STACK +static __always_inline void enable_shadow_stack(void) +{ + int ret; + + ret = my_syscall2(__NR_prctl, PR_SET_SHADOW_STACK_STATUS, + PR_SHADOW_STACK_ENABLE); + if (ret == 0) + shadow_stack_enabled = true; +} + +#endif + +#ifndef __NR_map_shadow_stack +#define __NR_map_shadow_stack 453 +#endif + +#ifndef ENABLE_SHADOW_STACK +static inline void enable_shadow_stack(void) { } +#endif + +#endif From patchwork Thu Feb 6 11:38:06 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Brown X-Patchwork-Id: 13962932 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D448B22C321; 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dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="GSREHtJx" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DE00AC4CEE2; Thu, 6 Feb 2025 11:40:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1738842035; bh=BNsC3bEhhpEgEjytHP4/YPGyhoBXglbmji5nqcOhkkQ=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=GSREHtJxwD6TLVsAUCUJoAQYSAFQ6jES1ixa7caqV0qeSNYOvSWHXBQABsFStq8eL qrZswHzKppnAxQAwtb5xCKoQhyxNYVqXOjc6tAyCWCxlILZwhv3AEBBsIPJU5urAYS +GKlRtgIoEohAhh+bjSFgKR1YqylkdNT8R0v0MAEbU2qLteS9ekNFHMkYQi0JIFGil tufJkUvgVkZH4HPKNGXLpGx3juQM1uYUKMSf0XNwh7wQNPkd12C59B76UtI/3ieUUm 08Jhm46kpNY5blwbwblaFux2nxfhdpgvPNxXPMGC+h8SO9h71YO6L2OwtU5LKtg8DF 47dJG50UY9SKg== From: Mark Brown Date: Thu, 06 Feb 2025 11:38:06 +0000 Subject: [PATCH RFT v14 4/8] fork: Add shadow stack support to clone3() Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <20250206-clone3-shadow-stack-v14-4-805b53af73b9@kernel.org> References: <20250206-clone3-shadow-stack-v14-0-805b53af73b9@kernel.org> In-Reply-To: <20250206-clone3-shadow-stack-v14-0-805b53af73b9@kernel.org> To: "Rick P. Edgecombe" , Deepak Gupta , Szabolcs Nagy , "H.J. Lu" , Florian Weimer , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Christian Brauner , Shuah Khan Cc: linux-kernel@vger.kernel.org, Catalin Marinas , Will Deacon , jannh@google.com, bsegall@google.com, Yury Khrustalev , Wilco Dijkstra , linux-kselftest@vger.kernel.org, linux-api@vger.kernel.org, Mark Brown , Kees Cook X-Mailer: b4 0.15-dev-1b0d6 X-Developer-Signature: v=1; a=openpgp-sha256; l=16815; i=broonie@kernel.org; h=from:subject:message-id; bh=BNsC3bEhhpEgEjytHP4/YPGyhoBXglbmji5nqcOhkkQ=; b=owEBbQGS/pANAwAKASTWi3JdVIfQAcsmYgBnpJ+RrsnrHTqqTUP/JJG9T1/hoTy1vGp/VV8qWKvF TDbRXHGJATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCZ6SfkQAKCRAk1otyXVSH0LCiB/ 4j0Hl2y6P7bMKhlP5ncl5ZJ5Q7YMnTKoctb4fdY3UYJuuwEKp20V+k6kto4tnut5a4/9KxEj4N5HDT IzEbrWG6fx2yysXj9AB1i5ppiKpA9dUZ1bAtdKq4mAL5a9MliMZn+jM3ce5EiVJbF+okO1L4Tz8JGQ JHpITXvFGKp3l9kRUCeyCPZncNJrV11rhbSsrrAQ9RaJFp9AAS5I6G2zEyOaTSuMpBGd2a0d518OB8 6yRgULwOwyfx8pto7mSchB/w2uiSv7CmZrqfIzeNUIYO6otBywgfaz8N/Dxrb/6cxs/D0hzwSN5mki 5liP2qwKPUm3u5MW1tB8j2IXc/JXzI X-Developer-Key: i=broonie@kernel.org; a=openpgp; fpr=3F2568AAC26998F9E813A1C5C3F436CA30F5D8EB Unlike with the normal stack there is no API for configuring the shadow stack for a new thread, instead the kernel will dynamically allocate a new shadow stack with the same size as the normal stack. This appears to be due to the shadow stack series having been in development since before the more extensible clone3() was added rather than anything more deliberate. Add a parameter to clone3() specifying the shadow stack pointer to use for the new thread, this is inconsistent with the way we specify the normal stack but during review concerns were expressed about having to identify where the shadow stack pointer should be placed especially in cases where the shadow stack has been previously active. If no shadow stack is specified then the existing implicit allocation behaviour is maintained. If a shadow stack pointer is specified then it is required to have an architecture defined token placed on the stack, this will be consumed by the new task. If no valid token is present then this will be reported with -EINVAL. This token prevents new threads being created pointing at the shadow stack of an existing running thread. If the architecture does not support shadow stacks the shadow stack pointer must be not be specified, architectures that do support the feature are expected to enforce the same requirement on individual systems that lack shadow stack support. Update the existing arm64 and x86 implementations to pay attention to the newly added arguments, in order to maintain compatibility we use the existing behaviour if no shadow stack is specified. Since we are now using more fields from the kernel_clone_args we pass that into the shadow stack code rather than individual fields. Portions of the x86 architecture code were written by Rick Edgecombe. Acked-by: Yury Khrustalev Signed-off-by: Mark Brown --- arch/arm64/mm/gcs.c | 54 +++++++++++++++++++++- arch/x86/include/asm/shstk.h | 11 +++-- arch/x86/kernel/process.c | 2 +- arch/x86/kernel/shstk.c | 57 +++++++++++++++++++++--- include/asm-generic/cacheflush.h | 11 +++++ include/linux/sched/task.h | 17 +++++++ include/uapi/linux/sched.h | 10 +++-- kernel/fork.c | 96 +++++++++++++++++++++++++++++++++++----- 8 files changed, 232 insertions(+), 26 deletions(-) diff --git a/arch/arm64/mm/gcs.c b/arch/arm64/mm/gcs.c index 1f633a482558b59aac5427963d42b37fce08c8a6..10ee92390ea1702793bef471452352463e464d2d 100644 --- a/arch/arm64/mm/gcs.c +++ b/arch/arm64/mm/gcs.c @@ -43,8 +43,24 @@ int gcs_alloc_thread_stack(struct task_struct *tsk, { unsigned long addr, size; - if (!system_supports_gcs()) + if (!system_supports_gcs()) { + if (args->shadow_stack_pointer) + return -EINVAL; + + return 0; + } + + /* + * If the user specified a GCS then use it, otherwise fall + * back to a default allocation strategy. Validation is done + * in arch_shstk_validate_clone(). + */ + if (args->shadow_stack_pointer) { + tsk->thread.gcs_base = 0; + tsk->thread.gcs_size = 0; + tsk->thread.gcspr_el0 = args->shadow_stack_pointer; return 0; + } if (!task_gcs_el0_enabled(tsk)) return 0; @@ -68,6 +84,42 @@ int gcs_alloc_thread_stack(struct task_struct *tsk, return 0; } +static bool gcs_consume_token(struct vm_area_struct *vma, struct page *page, + unsigned long user_addr) +{ + u64 expected = GCS_CAP(user_addr); + u64 *token = page_address(page) + offset_in_page(user_addr); + + if (!cmpxchg_to_user_page(vma, page, user_addr, token, expected, 0)) + return false; + set_page_dirty_lock(page); + + return true; +} + +int arch_shstk_validate_clone(struct task_struct *tsk, + struct vm_area_struct *vma, + struct page *page, + struct kernel_clone_args *args) +{ + unsigned long gcspr_el0; + int ret = 0; + + /* Ensure that a token written as a result of a pivot is visible */ + gcsb_dsync(); + + gcspr_el0 = args->shadow_stack_pointer; + if (!gcs_consume_token(vma, page, gcspr_el0)) + return -EINVAL; + + tsk->thread.gcspr_el0 = gcspr_el0 + sizeof(u64); + + /* Ensure that our token consumption visible */ + gcsb_dsync(); + + return ret; +} + SYSCALL_DEFINE3(map_shadow_stack, unsigned long, addr, unsigned long, size, unsigned int, flags) { unsigned long alloc_size; diff --git a/arch/x86/include/asm/shstk.h b/arch/x86/include/asm/shstk.h index 4cb77e004615dff003426a2eb594460ca1015f4e..252feeda69991e939942c74556e23e27c835e766 100644 --- a/arch/x86/include/asm/shstk.h +++ b/arch/x86/include/asm/shstk.h @@ -6,6 +6,7 @@ #include struct task_struct; +struct kernel_clone_args; struct ksignal; #ifdef CONFIG_X86_USER_SHADOW_STACK @@ -16,8 +17,8 @@ struct thread_shstk { long shstk_prctl(struct task_struct *task, int option, unsigned long arg2); void reset_thread_features(void); -unsigned long shstk_alloc_thread_stack(struct task_struct *p, unsigned long clone_flags, - unsigned long stack_size); +unsigned long shstk_alloc_thread_stack(struct task_struct *p, + const struct kernel_clone_args *args); void shstk_free(struct task_struct *p); int setup_signal_shadow_stack(struct ksignal *ksig); int restore_signal_shadow_stack(void); @@ -28,8 +29,10 @@ static inline long shstk_prctl(struct task_struct *task, int option, unsigned long arg2) { return -EINVAL; } static inline void reset_thread_features(void) {} static inline unsigned long shstk_alloc_thread_stack(struct task_struct *p, - unsigned long clone_flags, - unsigned long stack_size) { return 0; } + const struct kernel_clone_args *args) +{ + return 0; +} static inline void shstk_free(struct task_struct *p) {} static inline int setup_signal_shadow_stack(struct ksignal *ksig) { return 0; } static inline int restore_signal_shadow_stack(void) { return 0; } diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 6da6769d7254a46d87118ac016ede70d3f56f020..b56188ef5db27b5b5cf9fb4dfafce3746571a598 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -208,7 +208,7 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args) * is disabled, new_ssp will remain 0, and fpu_clone() will know not to * update it. */ - new_ssp = shstk_alloc_thread_stack(p, clone_flags, args->stack_size); + new_ssp = shstk_alloc_thread_stack(p, args); if (IS_ERR_VALUE(new_ssp)) return PTR_ERR((void *)new_ssp); diff --git a/arch/x86/kernel/shstk.c b/arch/x86/kernel/shstk.c index 059685612362d7b1865eabf400888fbfa0659c1e..056e2c9ec30531d0901297da07f1842b47d2fcd5 100644 --- a/arch/x86/kernel/shstk.c +++ b/arch/x86/kernel/shstk.c @@ -191,18 +191,65 @@ void reset_thread_features(void) current->thread.features_locked = 0; } -unsigned long shstk_alloc_thread_stack(struct task_struct *tsk, unsigned long clone_flags, - unsigned long stack_size) +int arch_shstk_validate_clone(struct task_struct *t, + struct vm_area_struct *vma, + struct page *page, + struct kernel_clone_args *args) +{ + /* + * SSP is aligned, so reserved bits and mode bit are a zero, just mark + * the token 64-bit. + */ + void *maddr = kmap_local_page(page); + int offset; + unsigned long addr, ssp; + u64 expected; + + if (!features_enabled(ARCH_SHSTK_SHSTK)) + return 0; + + ssp = args->shadow_stack_pointer; + addr = ssp - SS_FRAME_SIZE; + expected = ssp | BIT(0); + offset = offset_in_page(addr); + + if (!cmpxchg_to_user_page(vma, page, addr, (unsigned long *)(maddr + offset), + expected, 0)) + return -EINVAL; + set_page_dirty_lock(page); + + return 0; +} + +unsigned long shstk_alloc_thread_stack(struct task_struct *tsk, + const struct kernel_clone_args *args) { struct thread_shstk *shstk = &tsk->thread.shstk; + unsigned long clone_flags = args->flags; unsigned long addr, size; /* * If shadow stack is not enabled on the new thread, skip any - * switch to a new shadow stack. + * implicit switch to a new shadow stack and reject attempts to + * explicitly specify one. */ - if (!features_enabled(ARCH_SHSTK_SHSTK)) + if (!features_enabled(ARCH_SHSTK_SHSTK)) { + if (args->shadow_stack_pointer) + return (unsigned long)ERR_PTR(-EINVAL); + return 0; + } + + /* + * If the user specified a shadow stack then use it, otherwise + * fall back to a default allocation strategy. Validation is + * done in arch_shstk_validate_clone(). + */ + if (args->shadow_stack_pointer) { + shstk->base = 0; + shstk->size = 0; + return args->shadow_stack_pointer; + } /* * For CLONE_VFORK the child will share the parents shadow stack. @@ -222,7 +269,7 @@ unsigned long shstk_alloc_thread_stack(struct task_struct *tsk, unsigned long cl if (!(clone_flags & CLONE_VM)) return 0; - size = adjust_shstk_size(stack_size); + size = adjust_shstk_size(args->stack_size); addr = alloc_shstk(0, size, 0, false); if (IS_ERR_VALUE(addr)) return addr; diff --git a/include/asm-generic/cacheflush.h b/include/asm-generic/cacheflush.h index 7ee8a179d1036e1d8010b8b18a8f3022e41c1695..96cc0c7a5c90fd7e899d0c5fe7c706302265efcf 100644 --- a/include/asm-generic/cacheflush.h +++ b/include/asm-generic/cacheflush.h @@ -124,4 +124,15 @@ static inline void flush_cache_vunmap(unsigned long start, unsigned long end) } while (0) #endif +#ifndef cmpxchg_to_user_page +#define cmpxchg_to_user_page(vma, page, vaddr, ptr, old, new) \ +({ \ + bool ret; \ + \ + ret = try_cmpxchg(ptr, &old, new); \ + flush_icache_user_page(vma, page, vaddr, sizeof(*ptr)); \ + ret; \ +}) +#endif + #endif /* _ASM_GENERIC_CACHEFLUSH_H */ diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h index 0f2aeb37bbb047335a399326b31bc8df81b75a3a..cd36389619d5c97401f7b90e177c6027c232783b 100644 --- a/include/linux/sched/task.h +++ b/include/linux/sched/task.h @@ -16,6 +16,7 @@ struct task_struct; struct rusage; union thread_union; struct css_set; +struct vm_area_struct; /* All the bits taken by the old clone syscall. */ #define CLONE_LEGACY_FLAGS 0xffffffffULL @@ -43,6 +44,7 @@ struct kernel_clone_args { void *fn_arg; struct cgroup *cgrp; struct css_set *cset; + unsigned long shadow_stack_pointer; }; /* @@ -236,4 +238,19 @@ static inline void task_unlock(struct task_struct *p) DEFINE_GUARD(task_lock, struct task_struct *, task_lock(_T), task_unlock(_T)) +#ifdef CONFIG_ARCH_HAS_USER_SHADOW_STACK +int arch_shstk_validate_clone(struct task_struct *p, + struct vm_area_struct *vma, + struct page *page, + struct kernel_clone_args *args); +#else +static inline int arch_shstk_validate_clone(struct task_struct *p, + struct vm_area_struct *vma, + struct page *page, + struct kernel_clone_args *args) +{ + return 0; +} +#endif + #endif /* _LINUX_SCHED_TASK_H */ diff --git a/include/uapi/linux/sched.h b/include/uapi/linux/sched.h index 359a14cc76a4038aeacef14b2915d5ce60d0cf44..586a1c05a4e4ca05584d4d500223bcf6c3add54c 100644 --- a/include/uapi/linux/sched.h +++ b/include/uapi/linux/sched.h @@ -84,6 +84,8 @@ * kernel's limit of nested PID namespaces. * @cgroup: If CLONE_INTO_CGROUP is specified set this to * a file descriptor for the cgroup. + * @shadow_stack_pointer: Value to use for shadow stack pointer in the + * child process. * * The structure is versioned by size and thus extensible. * New struct members must go at the end of the struct and @@ -101,12 +103,14 @@ struct clone_args { __aligned_u64 set_tid; __aligned_u64 set_tid_size; __aligned_u64 cgroup; + __aligned_u64 shadow_stack_pointer; }; #endif -#define CLONE_ARGS_SIZE_VER0 64 /* sizeof first published struct */ -#define CLONE_ARGS_SIZE_VER1 80 /* sizeof second published struct */ -#define CLONE_ARGS_SIZE_VER2 88 /* sizeof third published struct */ +#define CLONE_ARGS_SIZE_VER0 64 /* sizeof first published struct */ +#define CLONE_ARGS_SIZE_VER1 80 /* sizeof second published struct */ +#define CLONE_ARGS_SIZE_VER2 88 /* sizeof third published struct */ +#define CLONE_ARGS_SIZE_VER3 96 /* sizeof fourth published struct */ /* * Scheduling policies diff --git a/kernel/fork.c b/kernel/fork.c index 735405a9c5f323b16fdac3832320c255649b6e23..17eb698beaa7f0e3ff42887c5e44d848d91d4417 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -2136,6 +2136,51 @@ static void rv_task_fork(struct task_struct *p) #define rv_task_fork(p) do {} while (0) #endif +static int shstk_validate_clone(struct task_struct *p, + struct kernel_clone_args *args) +{ + struct mm_struct *mm; + struct vm_area_struct *vma; + struct page *page; + unsigned long addr; + int ret; + + if (!IS_ENABLED(CONFIG_ARCH_HAS_USER_SHADOW_STACK)) + return 0; + + if (!args->shadow_stack_pointer) + return 0; + + mm = get_task_mm(p); + if (!mm) + return -EFAULT; + + mmap_read_lock(mm); + + addr = untagged_addr_remote(mm, args->shadow_stack_pointer); + page = get_user_page_vma_remote(mm, addr, FOLL_FORCE | FOLL_WRITE, + &vma); + if (IS_ERR(page)) { + ret = -EFAULT; + goto out; + } + + if (!(vma->vm_flags & VM_SHADOW_STACK) || + !(vma->vm_flags & VM_WRITE)) { + ret = -EFAULT; + goto out_page; + } + + ret = arch_shstk_validate_clone(p, vma, page, args); + +out_page: + put_page(page); +out: + mmap_read_unlock(mm); + mmput(mm); + return ret; +} + /* * This creates a new process as a copy of the old one, * but does not actually start it yet. @@ -2410,6 +2455,9 @@ __latent_entropy struct task_struct *copy_process( if (retval) goto bad_fork_cleanup_namespaces; retval = copy_thread(p, args); + if (retval) + goto bad_fork_cleanup_io; + retval = shstk_validate_clone(p, args); if (retval) goto bad_fork_cleanup_io; @@ -2973,7 +3021,9 @@ noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs, CLONE_ARGS_SIZE_VER1); BUILD_BUG_ON(offsetofend(struct clone_args, cgroup) != CLONE_ARGS_SIZE_VER2); - BUILD_BUG_ON(sizeof(struct clone_args) != CLONE_ARGS_SIZE_VER2); + BUILD_BUG_ON(offsetofend(struct clone_args, shadow_stack_pointer) != + CLONE_ARGS_SIZE_VER3); + BUILD_BUG_ON(sizeof(struct clone_args) != CLONE_ARGS_SIZE_VER3); if (unlikely(usize > PAGE_SIZE)) return -E2BIG; @@ -3006,16 +3056,17 @@ noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs, return -EINVAL; *kargs = (struct kernel_clone_args){ - .flags = args.flags, - .pidfd = u64_to_user_ptr(args.pidfd), - .child_tid = u64_to_user_ptr(args.child_tid), - .parent_tid = u64_to_user_ptr(args.parent_tid), - .exit_signal = args.exit_signal, - .stack = args.stack, - .stack_size = args.stack_size, - .tls = args.tls, - .set_tid_size = args.set_tid_size, - .cgroup = args.cgroup, + .flags = args.flags, + .pidfd = u64_to_user_ptr(args.pidfd), + .child_tid = u64_to_user_ptr(args.child_tid), + .parent_tid = u64_to_user_ptr(args.parent_tid), + .exit_signal = args.exit_signal, + .stack = args.stack, + .stack_size = args.stack_size, + .tls = args.tls, + .set_tid_size = args.set_tid_size, + .cgroup = args.cgroup, + .shadow_stack_pointer = args.shadow_stack_pointer, }; if (args.set_tid && @@ -3056,6 +3107,27 @@ static inline bool clone3_stack_valid(struct kernel_clone_args *kargs) return true; } +/** + * clone3_shadow_stack_valid - check and prepare shadow stack + * @kargs: kernel clone args + * + * Verify that shadow stacks are only enabled if supported. + */ +static inline bool clone3_shadow_stack_valid(struct kernel_clone_args *kargs) +{ + if (!kargs->shadow_stack_pointer) + return true; + + if (!IS_ALIGNED(kargs->shadow_stack_pointer, sizeof(void *))) + return false; + + /* + * The architecture must check support on the specific + * machine. + */ + return IS_ENABLED(CONFIG_ARCH_HAS_USER_SHADOW_STACK); +} + static bool clone3_args_valid(struct kernel_clone_args *kargs) { /* Verify that no unknown flags are passed along. */ @@ -3078,7 +3150,7 @@ static bool clone3_args_valid(struct kernel_clone_args *kargs) kargs->exit_signal) return false; - if (!clone3_stack_valid(kargs)) + if (!clone3_stack_valid(kargs) || !clone3_shadow_stack_valid(kargs)) return false; return true; From patchwork Thu Feb 6 11:38:07 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Brown X-Patchwork-Id: 13962933 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0259922E401; Thu, 6 Feb 2025 11:40:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738842042; cv=none; b=AKGnmSy5ord2uStptln8cCOdESXzAKrTj60e4FMEqi+he/ja1kn2aPoLAf9Dk08y54xrAW+6DQ6a1HAnU7gIM87AdRiiwS+CnX3R6CQRzVIV1U8tJoapi9q3L3+2ZNcOymtMHvdpqNxKegDP9Kj7F+aMNfHb5pXD2mSHporfQDA= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738842042; c=relaxed/simple; bh=PnhVCE63r5J0w6Q+lF8rA/22EDQWPUEiFQtbWxOidH8=; 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Edgecombe" , Deepak Gupta , Szabolcs Nagy , "H.J. Lu" , Florian Weimer , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Christian Brauner , Shuah Khan Cc: linux-kernel@vger.kernel.org, Catalin Marinas , Will Deacon , jannh@google.com, bsegall@google.com, Yury Khrustalev , Wilco Dijkstra , linux-kselftest@vger.kernel.org, linux-api@vger.kernel.org, Mark Brown , Kees Cook , Kees Cook , Shuah Khan X-Mailer: b4 0.15-dev-1b0d6 X-Developer-Signature: v=1; a=openpgp-sha256; l=1170; i=broonie@kernel.org; h=from:subject:message-id; bh=PnhVCE63r5J0w6Q+lF8rA/22EDQWPUEiFQtbWxOidH8=; b=owEBbQGS/pANAwAKASTWi3JdVIfQAcsmYgBnpJ+SDt5MY/PeYn2i3MjDTGqPfut3rGjAzO4UGMQ5 rwFJFNiJATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCZ6SfkgAKCRAk1otyXVSH0JeLB/ 0aRBuFzEuX+vu9XGmqCIolu3o5bGLCbpfX0Q8Gh1mdNKDlIX7gBe84m2oewjRlRdUbE+/m9tlb2VrV sQS0xE1j30SQeJ3Aom8EYam9Io0JfMuy0jPLkeJ5O+ctqdcGs8wzdtX7cLr+rRuE9+ouQHcG8nONKZ 1LueuNhIgNPjJWuxJ1jzYppaZHPLN2l1Sm6bpodDDpfA+XhggTDoIL4s78lW7u0cmsripxWPsRsjyj 68/lqwnzN+le1OnGM3HOKtAwvknsPrKJCspZdIpV90g4dqWDOLZd5ojphKrlVu2afzeCDLYimuyAn1 aZPZiSRfXq6XGOqC5PIGYX8VmIp2qh X-Developer-Key: i=broonie@kernel.org; a=openpgp; fpr=3F2568AAC26998F9E813A1C5C3F436CA30F5D8EB Since there were widespread issues with output not being flushed the kselftest framework was modified to explicitly set the output streams unbuffered in commit 58e2847ad2e6 ("selftests: line buffer test program's stdout") so there is no need to explicitly flush in the clone3 tests. Reviewed-by: Kees Cook Tested-by: Kees Cook Acked-by: Shuah Khan Reviewed-by: Catalin Marinas Signed-off-by: Mark Brown --- tools/testing/selftests/clone3/clone3_selftests.h | 2 -- 1 file changed, 2 deletions(-) diff --git a/tools/testing/selftests/clone3/clone3_selftests.h b/tools/testing/selftests/clone3/clone3_selftests.h index 3d2663fe50ba56f011629e4f2eb68a72bcceb087..39b5dcba663c30b9fc2542d9a0d2686105ce5761 100644 --- a/tools/testing/selftests/clone3/clone3_selftests.h +++ b/tools/testing/selftests/clone3/clone3_selftests.h @@ -35,8 +35,6 @@ struct __clone_args { static pid_t sys_clone3(struct __clone_args *args, size_t size) { - fflush(stdout); - fflush(stderr); return syscall(__NR_clone3, args, size); } From patchwork Thu Feb 6 11:38:08 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Brown X-Patchwork-Id: 13962934 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0A89622CBC6; Thu, 6 Feb 2025 11:40:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738842048; cv=none; b=Pa8nztfQ5KOHSGdlmvnmLzGYQtmooVdwDeonr/dVfX9fhSzswEcrVZRpLGyMzEPPhoDSEzwa4RmWE3O1eoQBNiFqZgatTUxmDxJhktlUp0T+IWI87V/LwiwI2zLiAqr/mjPqlMUdvi9y4DMEfhH8987Ypd+yxb+3+H7xTyVh2KE= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738842048; c=relaxed/simple; bh=wcvwqUbnOLAAxDrogxdDS6u/ZDM3Aldxt+7Gj0ApJNU=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=VthO0xZCgg1iaKP0/F2rqYcknxNXrYUUti/a47iCTF37GQWzGklEZIKfOX4BVYfS9a5A/NzrjPzLXXNxeM9CoVXFE6hUvj4ImpLV8EUA50ORB63i+EdnYlhe2vfHHL5wfu/trQRhNLi+kbgsFbLwQpoWfB80tVVt4yS/1fcjQr0= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=KsoRdlYC; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="KsoRdlYC" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DC18FC4CEDD; Thu, 6 Feb 2025 11:40:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1738842047; bh=wcvwqUbnOLAAxDrogxdDS6u/ZDM3Aldxt+7Gj0ApJNU=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=KsoRdlYCZd/SAQcW1gvI799ibhtCmAhdHJkjVpyTimgGjJCwRHeGxm1fUPPV6wgfo ihQg/EOxc9SKXjpFGxwfLzhjypZp8ywoqzZjIFnPnv+9Y40sjiVrWznMzuiLTzD4DH yifN2r/l33LZWXeL8Svhyt3EEXZeVSdiUC1vWtN8ZxRdZnJTv+6Pca7KY1FzRjeBIg 5RkNrmsb+r8PJPZy9GRH4NcZeixCeYL6N/WIqo+TDeSnSmJSWGiTztwrqVeOVbIfu7 wOoTZOtAgr9OMZjR7aBMMVTgrvqB9fPffvq9qPWKBohsx8lFdsib0MBgPhhLdMux7T Gba9J2BjRgUFw== From: Mark Brown Date: Thu, 06 Feb 2025 11:38:08 +0000 Subject: [PATCH RFT v14 6/8] selftests/clone3: Factor more of main loop into test_clone3() Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <20250206-clone3-shadow-stack-v14-6-805b53af73b9@kernel.org> References: <20250206-clone3-shadow-stack-v14-0-805b53af73b9@kernel.org> In-Reply-To: <20250206-clone3-shadow-stack-v14-0-805b53af73b9@kernel.org> To: "Rick P. Edgecombe" , Deepak Gupta , Szabolcs Nagy , "H.J. Lu" , Florian Weimer , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Christian Brauner , Shuah Khan Cc: linux-kernel@vger.kernel.org, Catalin Marinas , Will Deacon , jannh@google.com, bsegall@google.com, Yury Khrustalev , Wilco Dijkstra , linux-kselftest@vger.kernel.org, linux-api@vger.kernel.org, Mark Brown , Kees Cook , Kees Cook , Shuah Khan X-Mailer: b4 0.15-dev-1b0d6 X-Developer-Signature: v=1; a=openpgp-sha256; l=3987; i=broonie@kernel.org; h=from:subject:message-id; bh=wcvwqUbnOLAAxDrogxdDS6u/ZDM3Aldxt+7Gj0ApJNU=; b=owEBbQGS/pANAwAKASTWi3JdVIfQAcsmYgBnpJ+SfujCcQK6Uonhg58EJTuMpcGZA5C2px7/fz2O Q0Ce28yJATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCZ6SfkgAKCRAk1otyXVSH0BHgB/ 9/DZIUmBRhKAqRPmR8kmu7XGlL8FM3CL8oiaLajbDwHMQDAW+SMAX+2UV2zuQlDJnew7bz+7eyGcdW KCfdrcPgvu5X18U5t5dztpj3eZqch4y1Jk7v5aBsIc+VHLVZawSK1PP4ZQ+wHCqREBA1HvRBKYHvuV Le+oPjPA0oRfybVbSy8fWOBEiTXcB9fxomnbkSnDuZcw7iyds0BqXS9CB/ZIdD/hzdjkLUSbkDNZlW Gbbat+bN4kzTUBapEFBmgwRi4okmN5OEiCnrnqwYlzWzuJSavwYjWPxDzCtvRJSALYG+FBe4lGwJF+ IyoaM9x/9KYxr28+QiG7yBSWFnZDyK X-Developer-Key: i=broonie@kernel.org; a=openpgp; fpr=3F2568AAC26998F9E813A1C5C3F436CA30F5D8EB In order to make it easier to add more configuration for the tests and more support for runtime detection of when tests can be run pass the structure describing the tests into test_clone3() rather than picking the arguments out of it and have that function do all the per-test work. No functional change. Reviewed-by: Kees Cook Tested-by: Kees Cook Acked-by: Shuah Khan Reviewed-by: Catalin Marinas Signed-off-by: Mark Brown --- tools/testing/selftests/clone3/clone3.c | 77 ++++++++++++++++----------------- 1 file changed, 37 insertions(+), 40 deletions(-) diff --git a/tools/testing/selftests/clone3/clone3.c b/tools/testing/selftests/clone3/clone3.c index e61f07973ce5e27aff30047b35e03b1b51875c15..e066b201fa64eb17c55939b7cec18ac5d109613b 100644 --- a/tools/testing/selftests/clone3/clone3.c +++ b/tools/testing/selftests/clone3/clone3.c @@ -30,6 +30,19 @@ enum test_mode { CLONE3_ARGS_INVAL_EXIT_SIGNAL_NSIG, }; +typedef bool (*filter_function)(void); +typedef size_t (*size_function)(void); + +struct test { + const char *name; + uint64_t flags; + size_t size; + size_function size_function; + int expected; + enum test_mode test_mode; + filter_function filter; +}; + static int call_clone3(uint64_t flags, size_t size, enum test_mode test_mode) { struct __clone_args args = { @@ -109,30 +122,40 @@ static int call_clone3(uint64_t flags, size_t size, enum test_mode test_mode) return 0; } -static bool test_clone3(uint64_t flags, size_t size, int expected, - enum test_mode test_mode) +static void test_clone3(const struct test *test) { + size_t size; int ret; + if (test->filter && test->filter()) { + ksft_test_result_skip("%s\n", test->name); + return; + } + + if (test->size_function) + size = test->size_function(); + else + size = test->size; + + ksft_print_msg("Running test '%s'\n", test->name); + ksft_print_msg( "[%d] Trying clone3() with flags %#" PRIx64 " (size %zu)\n", - getpid(), flags, size); - ret = call_clone3(flags, size, test_mode); + getpid(), test->flags, size); + ret = call_clone3(test->flags, size, test->test_mode); ksft_print_msg("[%d] clone3() with flags says: %d expected %d\n", - getpid(), ret, expected); - if (ret != expected) { + getpid(), ret, test->expected); + if (ret != test->expected) { ksft_print_msg( "[%d] Result (%d) is different than expected (%d)\n", - getpid(), ret, expected); - return false; + getpid(), ret, test->expected); + ksft_test_result_fail("%s\n", test->name); + return; } - return true; + ksft_test_result_pass("%s\n", test->name); } -typedef bool (*filter_function)(void); -typedef size_t (*size_function)(void); - static bool not_root(void) { if (getuid() != 0) { @@ -160,16 +183,6 @@ static size_t page_size_plus_8(void) return getpagesize() + 8; } -struct test { - const char *name; - uint64_t flags; - size_t size; - size_function size_function; - int expected; - enum test_mode test_mode; - filter_function filter; -}; - static const struct test tests[] = { { .name = "simple clone3()", @@ -319,24 +332,8 @@ int main(int argc, char *argv[]) ksft_set_plan(ARRAY_SIZE(tests)); test_clone3_supported(); - for (i = 0; i < ARRAY_SIZE(tests); i++) { - if (tests[i].filter && tests[i].filter()) { - ksft_test_result_skip("%s\n", tests[i].name); - continue; - } - - if (tests[i].size_function) - size = tests[i].size_function(); - else - size = tests[i].size; - - ksft_print_msg("Running test '%s'\n", tests[i].name); - - ksft_test_result(test_clone3(tests[i].flags, size, - tests[i].expected, - tests[i].test_mode), - "%s\n", tests[i].name); - } + for (i = 0; i < ARRAY_SIZE(tests); i++) + test_clone3(&tests[i]); ksft_finished(); } From patchwork Thu Feb 6 11:38:09 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Brown X-Patchwork-Id: 13962935 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A7D0D22ACEE; Thu, 6 Feb 2025 11:40:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738842053; cv=none; b=STxhtypndhkJmdFEKEHaO4nY7HGhv5Pg0+JNGqEaPjYuRbG9Pu+q6R67BurSnbjvo3v9gRcHmq4Jx6hetWldKZJpJ71p8TBos1tk1Us/W9mSXbmBAg1Ljhl5icYtMJFaURtpyOaY/RA19hKh2juCg8FpFthm2JETbPF8UiysGzA= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; 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Edgecombe" , Deepak Gupta , Szabolcs Nagy , "H.J. Lu" , Florian Weimer , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Christian Brauner , Shuah Khan Cc: linux-kernel@vger.kernel.org, Catalin Marinas , Will Deacon , jannh@google.com, bsegall@google.com, Yury Khrustalev , Wilco Dijkstra , linux-kselftest@vger.kernel.org, linux-api@vger.kernel.org, Mark Brown , Kees Cook , Kees Cook , Shuah Khan X-Mailer: b4 0.15-dev-1b0d6 X-Developer-Signature: v=1; a=openpgp-sha256; l=2131; i=broonie@kernel.org; h=from:subject:message-id; bh=3K2UKwx+vuFRYwPgSWWdw27/XxZ/PQnIsnZQ3nrGTtc=; b=owEBbQGS/pANAwAKASTWi3JdVIfQAcsmYgBnpJ+TMvo6K8pgPknB+3dXsat7K6AeWSkktTYZLcag mBySj6OJATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCZ6SfkwAKCRAk1otyXVSH0DGvB/ 9i4Nj7i8bjak6cLr2dDaXeGea3z5aLG6DU6i8NU5EZilFLX5/SFTVG9ssfMJc5epdZ0UuH9AFl9HO+ eWAtdS3vhz+ZAFof/F4bPialAXi+jMLDCejknkQROFidKwIF+htla3ZFiCdB3ckqDhxGVbxCzawjXR Oo3NWmVV/2CSHEmXmaqfoPXt0zDynYZ6w9DaIo2CEVJzq9/DfkcRhvdp+FllECsrpNGPTEp0ZGG8Sq 3RxnI7sAVxfP4K2FsMO39LzhBBed2EGjVsQ8xL1UEW7E4URnEH1nAi7Yd77GYD/+cDlrIYDTWeZU6N Xcn7qAoTo3sIZKqK3YeuG7DQiVM1lb X-Developer-Key: i=broonie@kernel.org; a=openpgp; fpr=3F2568AAC26998F9E813A1C5C3F436CA30F5D8EB The clone_args structure is extensible, with the syscall passing in the length of the structure. Inside the kernel we use copy_struct_from_user() to read the struct but this has the unfortunate side effect of silently accepting some overrun in the structure size providing the extra data is all zeros. This means that we can't discover the clone3() features that the running kernel supports by simply probing with various struct sizes. We need to check this for the benefit of test systems which run newer kselftests on old kernels. Add a flag which can be set on a test to indicate that clone3() may return -E2BIG due to the use of newer struct versions. Currently no tests need this but it will become an issue for testing clone3() support for shadow stacks, the support for shadow stacks is already present on x86. Reviewed-by: Kees Cook Tested-by: Kees Cook Acked-by: Shuah Khan Reviewed-by: Catalin Marinas Signed-off-by: Mark Brown --- tools/testing/selftests/clone3/clone3.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/tools/testing/selftests/clone3/clone3.c b/tools/testing/selftests/clone3/clone3.c index e066b201fa64eb17c55939b7cec18ac5d109613b..5b8b7d640e70132242fc6939450669acd0c534f9 100644 --- a/tools/testing/selftests/clone3/clone3.c +++ b/tools/testing/selftests/clone3/clone3.c @@ -39,6 +39,7 @@ struct test { size_t size; size_function size_function; int expected; + bool e2big_valid; enum test_mode test_mode; filter_function filter; }; @@ -146,6 +147,11 @@ static void test_clone3(const struct test *test) ksft_print_msg("[%d] clone3() with flags says: %d expected %d\n", getpid(), ret, test->expected); if (ret != test->expected) { + if (test->e2big_valid && ret == -E2BIG) { + ksft_print_msg("Test reported -E2BIG\n"); + ksft_test_result_skip("%s\n", test->name); + return; + } ksft_print_msg( "[%d] Result (%d) is different than expected (%d)\n", getpid(), ret, test->expected); From patchwork Thu Feb 6 11:38:10 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Brown X-Patchwork-Id: 13962936 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 298C622D4F8; Thu, 6 Feb 2025 11:40:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738842060; cv=none; b=YCdXjlzDp5RFw538JWNHcbqvq34pe67ZWUyQ/NwyhQKWYNVgXLJivDlTfDJPaLKJNs23ve7y62PU/hGC6lCZ2U6KYtDnmMwsvPTRXi6W6lx40GkaekXZs3/syS+ajxClcJ7oi77wcBN8QS7X2182mP0D8wMjuM3yrAI6VXXCjec= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738842060; c=relaxed/simple; bh=0dcZ5VnJSzQzXy7lWuZKoNRAtTnb7RT4UixgF/KWECs=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=qRhenEMa5vqsnz9o2lUd9KVoL8hT3Ndx7h8tOyPME4bKj81iRaMA6wu9oln+IUJMNmcXtWOAsfIm6KBoUHzUT6gLz/f08iBs1KpjM2HesrEskXw4g8YKiVRGCWMnXN1MI83b5bJXeZM/rT+qTKsCtUzw9VWLdV3F6l0cWNAUR4Y= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=mlOo875N; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="mlOo875N" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F25FCC4CEE2; Thu, 6 Feb 2025 11:40:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1738842059; bh=0dcZ5VnJSzQzXy7lWuZKoNRAtTnb7RT4UixgF/KWECs=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=mlOo875NiNMdOxSsuyWkNiYfSslfOKONczW7/YwKspZbBhuP0qBJDk4RD5O1/3Rn7 8VoTB1RT8lxH0dyGuVifVA1SXF7zuPHNW1NRFOr5q9XU/iFhxycMjGz1FFrJFPUNp5 hVr2V5+b6u65ze/Jn25TXzxDKpLoTW6JR8Nt/rMg9LBX0T0yG5f+FV2bI4ryck52rG PMfxN/YZhL2KIi43M5YJXPhrz0oBXr1JsCnecyFDEWb7sYmVYBu82fWW+DfDPqFxeS JPg8bCziKOyi9EkMqVZBvRiezNjzapBJc7EFd2kgVPEsPY1uc10XhauefilGEdftLJ ziQRBjG7EDIcQ== From: Mark Brown Date: Thu, 06 Feb 2025 11:38:10 +0000 Subject: [PATCH RFT v14 8/8] selftests/clone3: Test shadow stack support Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <20250206-clone3-shadow-stack-v14-8-805b53af73b9@kernel.org> References: <20250206-clone3-shadow-stack-v14-0-805b53af73b9@kernel.org> In-Reply-To: <20250206-clone3-shadow-stack-v14-0-805b53af73b9@kernel.org> To: "Rick P. Edgecombe" , Deepak Gupta , Szabolcs Nagy , "H.J. Lu" , Florian Weimer , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Christian Brauner , Shuah Khan Cc: linux-kernel@vger.kernel.org, Catalin Marinas , Will Deacon , jannh@google.com, bsegall@google.com, Yury Khrustalev , Wilco Dijkstra , linux-kselftest@vger.kernel.org, linux-api@vger.kernel.org, Mark Brown , Kees Cook , Shuah Khan X-Mailer: b4 0.15-dev-1b0d6 X-Developer-Signature: v=1; a=openpgp-sha256; l=10296; i=broonie@kernel.org; h=from:subject:message-id; bh=0dcZ5VnJSzQzXy7lWuZKoNRAtTnb7RT4UixgF/KWECs=; b=owEBbQGS/pANAwAKASTWi3JdVIfQAcsmYgBnpJ+UkLBP0UhGAH0NJkQnx9XLz5RNgdaHmuHnZzUt MR/z/I+JATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCZ6SflAAKCRAk1otyXVSH0NudB/ 0Uw4Mt4R3WE/mOs0vN0TmvOiw9z10imRYcYunATXs6gFandJpZrBzmI0PTDbW01A4j/5cj97sMX4n9 OT4kz2rylzG83VQD/1bF644ATfVAWHT1Vr1tmCzggHYpSSpkqpI2gTAw+HJtD4/1y7YFJiHqtKNSnC F0gMuw7mGgGEjHpkBL7h75a6Zc4TJdWtrJXkAJDj6LHrmP4cvw95uSQ5tlCPjrB64XxdCJ3iMVSfoX Iz5IQsM5uER/xjbZP40o0ebEtCP6iETnPXAljN8Yv0oZ8R+6krB2gLz4Len3s1H9b2KVZW83X3XD3L x7IvRpvlSIEH97SQYuPl5YLiijaw4P X-Developer-Key: i=broonie@kernel.org; a=openpgp; fpr=3F2568AAC26998F9E813A1C5C3F436CA30F5D8EB Add basic test coverage for specifying the shadow stack for a newly created thread via clone3(), including coverage of the newly extended argument structure. We check that a user specified shadow stack can be provided, and that invalid combinations of parameters are rejected. In order to facilitate testing on systems without userspace shadow stack support we manually enable shadow stacks on startup, this is architecture specific due to the use of an arch_prctl() on x86. Due to interactions with potential userspace locking of features we actually detect support for shadow stacks on the running system by attempting to allocate a shadow stack page during initialisation using map_shadow_stack(), warning if this succeeds when the enable failed. In order to allow testing of user configured shadow stacks on architectures with that feature we need to ensure that we do not return from the function where the clone3() syscall is called in the child process, doing so would trigger a shadow stack underflow. To do this we use inline assembly rather than the standard syscall wrapper to call clone3(). In order to avoid surprises we also use a syscall rather than the libc exit() function., this should be overly cautious. Acked-by: Shuah Khan Signed-off-by: Mark Brown --- tools/testing/selftests/clone3/clone3.c | 143 +++++++++++++++++++++- tools/testing/selftests/clone3/clone3_selftests.h | 63 ++++++++++ 2 files changed, 205 insertions(+), 1 deletion(-) diff --git a/tools/testing/selftests/clone3/clone3.c b/tools/testing/selftests/clone3/clone3.c index 5b8b7d640e70132242fc6939450669acd0c534f9..b0378d7418cc8b00caebc6f92f58280bc04b0f80 100644 --- a/tools/testing/selftests/clone3/clone3.c +++ b/tools/testing/selftests/clone3/clone3.c @@ -3,6 +3,7 @@ /* Based on Christian Brauner's clone3() example */ #define _GNU_SOURCE +#include #include #include #include @@ -11,6 +12,7 @@ #include #include #include +#include #include #include #include @@ -19,8 +21,12 @@ #include #include "../kselftest.h" +#include "../ksft_shstk.h" #include "clone3_selftests.h" +static bool shadow_stack_supported; +static size_t max_supported_args_size; + enum test_mode { CLONE3_ARGS_NO_TEST, CLONE3_ARGS_ALL_0, @@ -28,6 +34,10 @@ enum test_mode { CLONE3_ARGS_INVAL_EXIT_SIGNAL_NEG, CLONE3_ARGS_INVAL_EXIT_SIGNAL_CSIG, CLONE3_ARGS_INVAL_EXIT_SIGNAL_NSIG, + CLONE3_ARGS_SHADOW_STACK, + CLONE3_ARGS_SHADOW_STACK_MISALIGNED, + CLONE3_ARGS_SHADOW_STACK_NO_TOKEN, + CLONE3_ARGS_SHADOW_STACK_NORMAL_MEMORY, }; typedef bool (*filter_function)(void); @@ -44,6 +54,44 @@ struct test { filter_function filter; }; + +/* + * We check for shadow stack support by attempting to use + * map_shadow_stack() since features may have been locked by the + * dynamic linker resulting in spurious errors when we attempt to + * enable on startup. We warn if the enable failed. + */ +static void test_shadow_stack_supported(void) +{ + long ret; + + ret = syscall(__NR_map_shadow_stack, 0, getpagesize(), 0); + if (ret == -1) { + ksft_print_msg("map_shadow_stack() not supported\n"); + } else if ((void *)ret == MAP_FAILED) { + ksft_print_msg("Failed to map shadow stack\n"); + } else { + ksft_print_msg("Shadow stack supportd\n"); + shadow_stack_supported = true; + + if (!shadow_stack_enabled) + ksft_print_msg("Mapped but did not enable shadow stack\n"); + } +} + +static void *get_shadow_stack_page(unsigned long flags) +{ + unsigned long long page; + + page = syscall(__NR_map_shadow_stack, 0, getpagesize(), flags); + if ((void *)page == MAP_FAILED) { + ksft_print_msg("map_shadow_stack() failed: %d\n", errno); + return 0; + } + + return (void *)page; +} + static int call_clone3(uint64_t flags, size_t size, enum test_mode test_mode) { struct __clone_args args = { @@ -57,6 +105,7 @@ static int call_clone3(uint64_t flags, size_t size, enum test_mode test_mode) } args_ext; pid_t pid = -1; + void *p; int status; memset(&args_ext, 0, sizeof(args_ext)); @@ -89,6 +138,26 @@ static int call_clone3(uint64_t flags, size_t size, enum test_mode test_mode) case CLONE3_ARGS_INVAL_EXIT_SIGNAL_NSIG: args.exit_signal = 0x00000000000000f0ULL; break; + case CLONE3_ARGS_SHADOW_STACK: + p = get_shadow_stack_page(SHADOW_STACK_SET_TOKEN); + p += getpagesize() - sizeof(void *); + args.shadow_stack_pointer = (unsigned long long)p; + break; + case CLONE3_ARGS_SHADOW_STACK_MISALIGNED: + p = get_shadow_stack_page(SHADOW_STACK_SET_TOKEN); + p += getpagesize() - sizeof(void *) - 1; + args.shadow_stack_pointer = (unsigned long long)p; + break; + case CLONE3_ARGS_SHADOW_STACK_NORMAL_MEMORY: + p = malloc(getpagesize()); + p += getpagesize() - sizeof(void *); + args.shadow_stack_pointer = (unsigned long long)p; + break; + case CLONE3_ARGS_SHADOW_STACK_NO_TOKEN: + p = get_shadow_stack_page(0); + p += getpagesize() - sizeof(void *); + args.shadow_stack_pointer = (unsigned long long)p; + break; } memcpy(&args_ext.args, &args, sizeof(struct __clone_args)); @@ -102,7 +171,12 @@ static int call_clone3(uint64_t flags, size_t size, enum test_mode test_mode) if (pid == 0) { ksft_print_msg("I am the child, my PID is %d\n", getpid()); - _exit(EXIT_SUCCESS); + /* + * Use a raw syscall to ensure we don't get issues + * with manually specified shadow stack and exit handlers. + */ + syscall(__NR_exit, EXIT_SUCCESS); + ksft_print_msg("CHILD FAILED TO EXIT PID is %d\n", getpid()); } ksft_print_msg("I am the parent (%d). My child's pid is %d\n", @@ -184,6 +258,26 @@ static bool no_timenamespace(void) return true; } +static bool have_shadow_stack(void) +{ + if (shadow_stack_supported) { + ksft_print_msg("Shadow stack supported\n"); + return true; + } + + return false; +} + +static bool no_shadow_stack(void) +{ + if (!shadow_stack_supported) { + ksft_print_msg("Shadow stack not supported\n"); + return true; + } + + return false; +} + static size_t page_size_plus_8(void) { return getpagesize() + 8; @@ -327,6 +421,50 @@ static const struct test tests[] = { .expected = -EINVAL, .test_mode = CLONE3_ARGS_NO_TEST, }, + { + .name = "Shadow stack on system with shadow stack", + .size = 0, + .expected = 0, + .e2big_valid = true, + .test_mode = CLONE3_ARGS_SHADOW_STACK, + .filter = no_shadow_stack, + }, + { + .name = "Shadow stack with misaligned address", + .flags = CLONE_VM, + .size = 0, + .expected = -EINVAL, + .e2big_valid = true, + .test_mode = CLONE3_ARGS_SHADOW_STACK_MISALIGNED, + .filter = no_shadow_stack, + }, + { + .name = "Shadow stack with normal memory", + .flags = CLONE_VM, + .size = 0, + .expected = -EFAULT, + .e2big_valid = true, + .test_mode = CLONE3_ARGS_SHADOW_STACK_NORMAL_MEMORY, + .filter = no_shadow_stack, + }, + { + .name = "Shadow stack with no token", + .flags = CLONE_VM, + .size = 0, + .expected = -EINVAL, + .e2big_valid = true, + .test_mode = CLONE3_ARGS_SHADOW_STACK_NO_TOKEN, + .filter = no_shadow_stack, + }, + { + .name = "Shadow stack on system without shadow stack", + .flags = CLONE_VM, + .size = 0, + .expected = -EINVAL, + .e2big_valid = true, + .test_mode = CLONE3_ARGS_SHADOW_STACK, + .filter = have_shadow_stack, + }, }; int main(int argc, char *argv[]) @@ -334,9 +472,12 @@ int main(int argc, char *argv[]) size_t size; int i; + enable_shadow_stack(); + ksft_print_header(); ksft_set_plan(ARRAY_SIZE(tests)); test_clone3_supported(); + test_shadow_stack_supported(); for (i = 0; i < ARRAY_SIZE(tests); i++) test_clone3(&tests[i]); diff --git a/tools/testing/selftests/clone3/clone3_selftests.h b/tools/testing/selftests/clone3/clone3_selftests.h index 39b5dcba663c30b9fc2542d9a0d2686105ce5761..24d40860fe2a3c2e66731a8b2afe94c5d2dff278 100644 --- a/tools/testing/selftests/clone3/clone3_selftests.h +++ b/tools/testing/selftests/clone3/clone3_selftests.h @@ -31,12 +31,75 @@ struct __clone_args { __aligned_u64 set_tid; __aligned_u64 set_tid_size; __aligned_u64 cgroup; +#ifndef CLONE_ARGS_SIZE_VER2 +#define CLONE_ARGS_SIZE_VER2 88 /* sizeof third published struct */ +#endif + __aligned_u64 shadow_stack_pointer; +#ifndef CLONE_ARGS_SIZE_VER3 +#define CLONE_ARGS_SIZE_VER3 96 /* sizeof fourth published struct */ +#endif }; +/* + * For architectures with shadow stack support we need to be + * absolutely sure that the clone3() syscall will be inline and not a + * function call so we open code. + */ +#ifdef __x86_64__ +static __always_inline pid_t sys_clone3(struct __clone_args *args, size_t size) +{ + register long _num __asm__ ("rax") = __NR_clone3; + register long _args __asm__ ("rdi") = (long)(args); + register long _size __asm__ ("rsi") = (long)(size); + long ret; + + __asm__ volatile ( + "syscall\n" + : "=a"(ret) + : "r"(_args), "r"(_size), + "0"(_num) + : "rcx", "r11", "memory", "cc" + ); + + if (ret < 0) { + errno = -ret; + return -1; + } + + return ret; +} +#elif defined(__aarch64__) +static __always_inline pid_t sys_clone3(struct __clone_args *args, size_t size) +{ + register long _num __asm__ ("x8") = __NR_clone3; + register long _args __asm__ ("x0") = (long)(args); + register long _size __asm__ ("x1") = (long)(size); + register long arg2 __asm__ ("x2") = 0; + register long arg3 __asm__ ("x3") = 0; + register long arg4 __asm__ ("x4") = 0; + + __asm__ volatile ( + "svc #0\n" + : "=r"(_args) + : "r"(_args), "r"(_size), + "r"(_num), "r"(arg2), + "r"(arg3), "r"(arg4) + : "memory", "cc" + ); + + if ((int)_args < 0) { + errno = -((int)_args); + return -1; + } + + return _args; +} +#else static pid_t sys_clone3(struct __clone_args *args, size_t size) { return syscall(__NR_clone3, args, size); } +#endif static inline void test_clone3_supported(void) {