From patchwork Mon Nov 20 23:54:28 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Brown X-Patchwork-Id: 13462291 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 1C4C83B786; Mon, 20 Nov 2023 23:55:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="JYAZrAIT" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 213C5C433C8; Mon, 20 Nov 2023 23:55:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1700524522; bh=a/9neu1tFH+KJoMSs60BVIB0GUVr2b3mTNMGBRScTUk=; h=From:Subject:Date:To:Cc:From; b=JYAZrAITo3f0CN1qCjUsi9Vrq+8+7jKeIfVoT45KT2zX/2A5Rr2KblHWs9MPX+m8K 2ez0uqC9h1O5ZcRIbKPiSsohDRTKlLZqeKvIIVZ+EUVeRuq0Zf03qGoh9tXVkyqpaO bZC6KDU7ajg0kVbbjANrLhq/knFkoh+eQFgp4R+MLgop8ASueQJm8iSIZpe5CUArnq sjGT20Zvyt2OMEj6ovhiW7DKP3G0ykDsgS/OGZ9VUsrHgVLu8zZd7tmUZ+jAWSVA6O N6smpgKwib5vO60jvWpsGhasCKZ/+QGbbuNJ3FDNM4Yz++2/AFO2/2Wsh6TaAZctr0 YnWK/dbZ8X+Kg== From: Mark Brown Subject: [PATCH RFT v3 0/5] fork: Support shadow stacks in clone3() Date: Mon, 20 Nov 2023 23:54:28 +0000 Message-Id: <20231120-clone3-shadow-stack-v3-0-a7b8ed3e2acc@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=H4sIALXxW2UC/23NQQ7CIBAF0KsY1mIYKFhdufIAxp1x0ZZpS9qAg QY1Te8uwYUx6fLPz7w/k4DeYCDHzUw8RhOMsymI7YY0fWU7pEanTDjjAhgcaDM6i4KGvtLuScN UNQMFqQumed1KoUj6fHhszSurN3I5X8k9HXsTJuffeSlCrr4oF6toBMqoLtVeszr5mp0G9BbHn fNdBiP/IQDFOsITUisQbalKACn/kGVZPoNZvpIBAQAA 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 , Daniel Bristot de Oliveira , Valentin Schneider , Christian Brauner , Shuah Khan Cc: linux-kernel@vger.kernel.org, Catalin Marinas , Will Deacon , Kees Cook , jannh@google.com, bsegall@google.com, linux-kselftest@vger.kernel.org, linux-api@vger.kernel.org, Mark Brown , David Hildenbrand X-Mailer: b4 0.13-dev-0438c X-Developer-Signature: v=1; a=openpgp-sha256; l=4572; i=broonie@kernel.org; h=from:subject:message-id; bh=a/9neu1tFH+KJoMSs60BVIB0GUVr2b3mTNMGBRScTUk=; b=owEBbQGS/pANAwAKASTWi3JdVIfQAcsmYgBlW/He+R9tbOuG3iCWWr+KroLJVc1KteepSJ28g1T0 o7YadV2JATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCZVvx3gAKCRAk1otyXVSH0M9yB/ 4glbrgSuL+qqlZo7pncWnZALQCHVi6bW1l9IilkRhvgdoz8H2MSQ2YP59x56pa0uMUOQoSoHH5l4v+ Jjd7S3MDqc6TAuYwxmA4Vr6Bu74wm5etkRBbggKZEExxdu270I2gHsdx3CZzJ95ls2v2KsgGIHTOrY u9f5Amky+q7z+QcbPk9SJVj33XeKiBJgRFRQg/tK+xrAM/HZ3n/zIth3a+ys/nKNhjDcdLJqt6wYvk Z9lBOdYyMXQML24PyXvC6jyy5PRJaXgmo8EhLPcJy2zsUKNbQM+Okb54Kj1rrRZA9J2kJFI6xIxzLH zd/ls6HZZDHxG6V4SEu7lAVilp8STa 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 in a similar manner to how the normal stack is specified, keeping the current implicit allocation behaviour if one is not specified either with clone3() or through the use of clone(). Unlike normal stacks only the shadow stack size is specified, similar issues to those that lead to the creation of map_shadow_stack() apply. 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 avaible to me, I have done testing with an integration into my pending work for GCS. There is some possibility that the arm64 implementation may require the use of clone3() and explicit userspace allocation of shadow stacks, this is still under discussion. A new architecture feature Kconfig option for shadow stacks is added as here, this was suggested as part of the review comments for the arm64 GCS series and since we need to detect if shadow stacks are supported it seemed sensible to roll it in here. [1] https://lore.kernel.org/r/20231009-arm64-gcs-v6-0-78e55deaa4dd@kernel.org/ Signed-off-by: Mark Brown --- 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 (5): mm: Introduce ARCH_HAS_USER_SHADOW_STACK fork: Add shadow stack support to clone3() selftests/clone3: Factor more of main loop into test_clone3() selftests/clone3: Allow tests to flag if -E2BIG is a valid error code kselftest/clone3: Test shadow stack support arch/x86/Kconfig | 1 + arch/x86/include/asm/shstk.h | 11 +- arch/x86/kernel/process.c | 2 +- arch/x86/kernel/shstk.c | 59 +++++-- fs/proc/task_mmu.c | 2 +- include/linux/mm.h | 2 +- include/linux/sched/task.h | 1 + include/uapi/linux/sched.h | 4 + kernel/fork.c | 22 ++- mm/Kconfig | 6 + tools/testing/selftests/clone3/clone3.c | 200 +++++++++++++++++----- tools/testing/selftests/clone3/clone3_selftests.h | 7 + 12 files changed, 250 insertions(+), 67 deletions(-) --- base-commit: 98b1cc82c4affc16f5598d4fa14b1858671b2263 change-id: 20231019-clone3-shadow-stack-15d40d2bf536 Best regards,