From patchwork Tue Dec 3 18:43:34 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Brown X-Patchwork-Id: 13892807 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 CBF1A1632F3; Tue, 3 Dec 2024 18:43:55 +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=1733251435; cv=none; b=pqGSH13CAaDMYOktvkWCo3OXr3+IMEjHXOFORB0H/eE/HFmV2Q2Ryqb9fv/i+XanbZ0A7abfrP11wXsCEft7hy1uPUX+OHTBLO3SYKIepoiTuApKzpKmuf1wZuombhkGtvyOSykEKRo/jR4dm9wO2fBHh/IzUuMswam/GB25RhM= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733251435; c=relaxed/simple; bh=qMyvWLOMEYcXsb7codEeSmahMIrsZFObgjZPEP95daQ=; h=From:Subject:Date:Message-Id:MIME-Version:Content-Type:To:Cc; b=uXuxqu2La15+l8cGSIByDbPJ84S0NEMAYDKsTSMTTuAhbpZfdkUMNfKRFCjKxNtyzn8BYmAmKKBQa6c3mbRQDgCy12tuxoz8sS5Tx0M3KQnMdRtFumnTQISWmpaIj84vT/RF1Mrr4GtYbz3ZLIDrvaXaoU9nbzmOVnYu+cAjPR0= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=BJLc4Upq; 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="BJLc4Upq" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A9F77C4CECF; Tue, 3 Dec 2024 18:43:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1733251435; bh=qMyvWLOMEYcXsb7codEeSmahMIrsZFObgjZPEP95daQ=; h=From:Subject:Date:To:Cc:From; b=BJLc4UpqPSYFc2ysDjcNqjir97j0+fFGgn3vQTd5+oTMXtSxqK+425xstL8MzxtXk ptOKtZZb8f0tR+hnPLNr3qnuVn2Voe8lt6a7/mulTeRH5TQ4nXttMfK+KxK5Fp4488 2mPdDe5Ekx2xLXBcfrQj0HGX4iePGb0HDe5PfUVab4Cl4ML6sX4AwK2wUgzzNRywsZ RglAuaKZcOG61/P2c2ojExDyqAKto+RPIjPKHZXE/roj30BHC6bX8HOSPKB4G/9gIQ 8C/vzicF7vI3e84+UckFpju4dleB+UORglBJUCJFDOPAxA9Xsr0PNN1eSd62bxZHx2 mMxWuk0pngSCw== From: Mark Brown Subject: [PATCH RFT v13 0/8] fork: Support shadow stacks in clone3() Date: Tue, 03 Dec 2024 18:43:34 +0000 Message-Id: <20241203-clone3-shadow-stack-v13-0-93b89a81a5ed@kernel.org> Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-B4-Tracking: v=1; b=H4sIAFZRT2cC/3XSTU7DMBAF4KtUXhPkGf+zYsUBEDvEwo7HbdQqQ UkVQFXvjhMEDXKytC1/9jy9Cxuob2hgD7sL62lshqZr8wLE3Y7VB9/uqWpi3mDIUQAHV9WnriV RDQcfu49qOPv6WIGKkkcMSQnN8s33nlLzObOv7Pnphb3lzUMznLv+a35qhPnoB0Wxio5Q8Spab SIP2Y/88Uh9S6f7rt/P4Ig3BECuI5iRoEEkqy2AUgUiFgjydURkxJtgKQpCX9cFIpeIXUdkRmx AmxLJpI0uEPWLSI58IxOVEYFYa6ecJRkKRN8QvRWszogjMsaKACm4AjE3xAhYR8yUiVMCiUIKE AvE3hDLNzKxGeG+TsLUPoEsg3ULZKN8o5vG0RiNTM5JLQsE+ELBjXmAT3/RZI0zwUlZNgX+Siu Bc7XBTK1Frz2GqKNWUDK4YLbSham3BqygYAMRmH/M9Xr9BmbmC3y6AwAA X-Change-ID: 20231019-clone3-shadow-stack-15d40d2bf536 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-9b746 X-Developer-Signature: v=1; a=openpgp-sha256; l=7498; i=broonie@kernel.org; h=from:subject:message-id; bh=qMyvWLOMEYcXsb7codEeSmahMIrsZFObgjZPEP95daQ=; b=owEBbQGS/pANAwAKASTWi3JdVIfQAcsmYgBnT1Fe8J3zqap41wMLj5MppVFw6YmUje+1n+UxE2+S o0xLhmeJATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCZ09RXgAKCRAk1otyXVSH0Be7B/ 93D3P81HJ10uBRoTb/Docn0nkvZ/zPWamPs5r0Y7urJ+tNnV1L81JJLzSn9W9Gg6LsU/z9/ogq/d51 jslDXsKG0zEM30uD8vpOGk2L9AVyVDFhRJCeEHdNVJ+ceM5ibT7RqVZ9gLGiyeoBw7GLue2TaOmihz d26MxtGZbcYQVqHpXWMNK+f9XH0DlsZ2DMX4drBUPyRfoMihxwSDDy/HKzJ9LRzsI4H0MZwsuJyo0c 8dDQYPPEFjgOIghv9TsGb8moVfkM4cPQe4/qAeineY84X2/sje6pp3E8P7584l3uXqsVoNI4Orklzb kB2D5gSXjNCPZ2gy5Tb9aTM5TTMScu X-Developer-Key: i=broonie@kernel.org; a=openpgp; fpr=3F2568AAC26998F9E813A1C5C3F436CA30F5D8EB The kernel has recently added support for shadow stacks, currently x86 only using their CET feature but both arm64 and RISC-V have equivalent features (GCS and Zicfiss respectively), I am actively working on GCS[1]. With shadow stacks the hardware maintains an additional stack containing only the return addresses for branch instructions which is not generally writeable by userspace and ensures that any returns are to the recorded addresses. This provides some protection against ROP attacks and making it easier to collect call stacks. These shadow stacks are allocated in the address space of the userspace process. Our API for shadow stacks does not currently offer userspace any flexiblity for managing the allocation of shadow stacks for newly created threads, instead the kernel allocates a new shadow stack with the same size as the normal stack whenever a thread is created with the feature enabled. The stacks allocated in this way are freed by the kernel when the thread exits or shadow stacks are disabled for the thread. This lack of flexibility and control isn't ideal, in the vast majority of cases the shadow stack will be over allocated and the implicit allocation and deallocation is not consistent with other interfaces. As far as I can tell the interface is done in this manner mainly because the shadow stack patches were in development since before clone3() was implemented. Since clone3() is readily extensible let's add support for specifying a shadow stack when creating a new thread or process, keeping the current implicit allocation behaviour if one is not specified either with clone3() or through the use of clone(). The user must provide a shadow stack pointer, this must point to memory mapped for use as a shadow stackby map_shadow_stack() with an architecture specified shadow stack token at the top of the stack. Please note that the x86 portions of this code are build tested only, I don't appear to have a system that can run CET available to me. [1] https://lore.kernel.org/linux-arm-kernel/20241001-arm64-gcs-v13-0-222b78d87eee@kernel.org/T/#mc58f97f27461749ccf400ebabf6f9f937116a86b Signed-off-by: Mark Brown --- Changes in v13: - Rebase onto v6.13-rc1. - Link to v12: https://lore.kernel.org/r/20241031-clone3-shadow-stack-v12-0-7183eb8bee17@kernel.org Changes in v12: - Add the regular prctl() to the userspace API document since arm64 support is queued in -next. - Link to v11: https://lore.kernel.org/r/20241005-clone3-shadow-stack-v11-0-2a6a2bd6d651@kernel.org Changes in v11: - Rebase onto arm64 for-next/gcs, which is based on v6.12-rc1, and integrate arm64 support. - Rework the interface to specify a shadow stack pointer rather than a base and size like we do for the regular stack. - Link to v10: https://lore.kernel.org/r/20240821-clone3-shadow-stack-v10-0-06e8797b9445@kernel.org Changes in v10: - Integrate fixes & improvements for the x86 implementation from Rick Edgecombe. - Require that the shadow stack be VM_WRITE. - Require that the shadow stack base and size be sizeof(void *) aligned. - Clean up trailing newline. - Link to v9: https://lore.kernel.org/r/20240819-clone3-shadow-stack-v9-0-962d74f99464@kernel.org Changes in v9: - Pull token validation earlier and report problems with an error return to parent rather than signal delivery to the child. - Verify that the top of the supplied shadow stack is VM_SHADOW_STACK. - Rework token validation to only do the page mapping once. - Drop no longer needed support for testing for signals in selftest. - Fix typo in comments. - Link to v8: https://lore.kernel.org/r/20240808-clone3-shadow-stack-v8-0-0acf37caf14c@kernel.org Changes in v8: - Fix token verification with user specified shadow stack. - Don't track user managed shadow stacks for child processes. - Link to v7: https://lore.kernel.org/r/20240731-clone3-shadow-stack-v7-0-a9532eebfb1d@kernel.org Changes in v7: - Rebase onto v6.11-rc1. - Typo fixes. - Link to v6: https://lore.kernel.org/r/20240623-clone3-shadow-stack-v6-0-9ee7783b1fb9@kernel.org Changes in v6: - Rebase onto v6.10-rc3. - Ensure we don't try to free the parent shadow stack in error paths of x86 arch code. - Spelling fixes in userspace API document. - Additional cleanups and improvements to the clone3() tests to support the shadow stack tests. - Link to v5: https://lore.kernel.org/r/20240203-clone3-shadow-stack-v5-0-322c69598e4b@kernel.org Changes in v5: - Rebase onto v6.8-rc2. - Rework ABI to have the user allocate the shadow stack memory with map_shadow_stack() and a token. - Force inlining of the x86 shadow stack enablement. - Move shadow stack enablement out into a shared header for reuse by other tests. - Link to v4: https://lore.kernel.org/r/20231128-clone3-shadow-stack-v4-0-8b28ffe4f676@kernel.org Changes in v4: - Formatting changes. - Use a define for minimum shadow stack size and move some basic validation to fork.c. - Link to v3: https://lore.kernel.org/r/20231120-clone3-shadow-stack-v3-0-a7b8ed3e2acc@kernel.org Changes in v3: - Rebase onto v6.7-rc2. - Remove stale shadow_stack in internal kargs. - If a shadow stack is specified unconditionally use it regardless of CLONE_ parameters. - Force enable shadow stacks in the selftest. - Update changelogs for RISC-V feature rename. - Link to v2: https://lore.kernel.org/r/20231114-clone3-shadow-stack-v2-0-b613f8681155@kernel.org Changes in v2: - Rebase onto v6.7-rc1. - Remove ability to provide preallocated shadow stack, just specify the desired size. - Link to v1: https://lore.kernel.org/r/20231023-clone3-shadow-stack-v1-0-d867d0b5d4d0@kernel.org --- Mark Brown (8): arm64/gcs: Return a success value from gcs_alloc_thread_stack() Documentation: userspace-api: Add shadow stack API documentation selftests: Provide helper header for shadow stack testing fork: Add shadow stack support to clone3() selftests/clone3: Remove redundant flushes of output streams selftests/clone3: Factor more of main loop into test_clone3() selftests/clone3: Allow tests to flag if -E2BIG is a valid error code selftests/clone3: Test shadow stack support Documentation/userspace-api/index.rst | 1 + Documentation/userspace-api/shadow_stack.rst | 42 ++++ arch/arm64/include/asm/gcs.h | 8 +- arch/arm64/kernel/process.c | 8 +- arch/arm64/mm/gcs.c | 62 +++++- 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 +++++++-- tools/testing/selftests/clone3/clone3.c | 226 ++++++++++++++++++---- tools/testing/selftests/clone3/clone3_selftests.h | 65 ++++++- tools/testing/selftests/ksft_shstk.h | 98 ++++++++++ 15 files changed, 633 insertions(+), 81 deletions(-) --- base-commit: 40384c840ea1944d7c5a392e8975ed088ecf0b37 change-id: 20231019-clone3-shadow-stack-15d40d2bf536 Best regards,