From patchwork Thu Aug 8 08:15:21 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Brown X-Patchwork-Id: 13757095 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 6C6C16F30E; Thu, 8 Aug 2024 08:16:27 +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=1723104987; cv=none; b=GEHlYcAPnDUqpmz1QIemltgRAHr0BTqAjkCZId/xCPPeFck3uA+5ItaRD0M532/WRCgy82E86YpYS5PZCs+f9TtICs0wQtM6HDz2P6feTaDnBj4L9bC8cnX2fgKZjIL7LCALl6P5fOsD6QRxsrIw8AwqvbFwM7QB5ZTVgpQ9aQc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723104987; c=relaxed/simple; bh=tYfPWHQkb5HpeM9E7Nl8dJHKPDlLHCxfggIkjFxrTnE=; h=From:Subject:Date:Message-Id:MIME-Version:Content-Type:To:Cc; b=nWegpcqCVhfRlnwr81Az4Pu8BYDJrNqYG5ez+PZXf0TRUUUTNH5opiDPoqhR9E+7USer7mcNRnStElgic2893NIoa1FWxiPJQ9tCO4Xhs8GyF17Pgm05eynifFB/vmjAvX39iLDBbpFyV9qhQWUxhWXbCWEOnVIgdh6psBesrPk= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=l6tQ/84+; 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="l6tQ/84+" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7917AC32786; Thu, 8 Aug 2024 08:16:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1723104986; bh=tYfPWHQkb5HpeM9E7Nl8dJHKPDlLHCxfggIkjFxrTnE=; h=From:Subject:Date:To:Cc:From; b=l6tQ/84+jkwPCxlBTYrKQCc/9Vizesus8ynU1dzKk79AyCNfgt5Kma4d/4Jw4CtbL M/WmWVj+fOouekEAhG8qmXuIf49vNFPn5MnA5SArZ248a4jRq6jaFIL20PKj8p9vsP u2Y/QXQBG7A76mz55pexJt4DvF9SiGjJi5m+S+8gUFNm+NZdTUBUwBAxm3nIEODE5n sOb3MgXhZFbWF+Ft9F5RE3CADKZshOKowMCaGEER+FJsbqXgxB0kwWrFgjL5c7aOq9 MJXEuW0g31L6GDhOY2tMXl8WOHhPESGuBBO3FZlK8b/hNBfUoKfT/ezfaT5LwFSUAD Niufvxjr2gRsg== From: Mark Brown Subject: [PATCH RFT v8 0/9] fork: Support shadow stacks in clone3() Date: Thu, 08 Aug 2024 09:15:21 +0100 Message-Id: <20240808-clone3-shadow-stack-v8-0-0acf37caf14c@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=H4sIAJl+tGYC/3XQTU7DMBAF4KtUXmPkGf+zYsUBEDvEIo7HrdUqQ U4VQFXujglCKUq6fDOab6R3YQOVTAN72F1YoTEPue9qcHc71h6abk88x5oZCpQgwPP21Hck+XB oYv/Bh3PTHjnoqETEkLQ0rF6+F0r5c1Zf2fPTC3urw0Mezn35mj+NMK9+UZSb6Ahc8OiMjSJUP 4rHI5WOTvd92c/giAsCoLYRrEgwIJMzDkDrFSKvEBTbiKxIY4OjKAmbtl0h6hpx24iqiAvoUiK VjDUrRP8hSqC40YmuiERsjdfekQorxCyIuVWsqYgnstbJACn4FWIXxErYRuxPJ15LJAopQPyHT NP0DUqryadaAgAA 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, linux-kselftest@vger.kernel.org, linux-api@vger.kernel.org, Mark Brown , Kees Cook , David Hildenbrand X-Mailer: b4 0.15-dev-37811 X-Developer-Signature: v=1; a=openpgp-sha256; l=6701; i=broonie@kernel.org; h=from:subject:message-id; bh=tYfPWHQkb5HpeM9E7Nl8dJHKPDlLHCxfggIkjFxrTnE=; b=owEBbQGS/pANAwAKASTWi3JdVIfQAcsmYgBmtH7FMSZMSyV0Oaf1jOcV3spGdxsEzL2UEay2M Sc9EfXfuVGJATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCZrR+xQAKCRAk1otyXVSH 0CJTB/0fEFx5Dd5GjJ6FB55c4W0450ayb0bsg3OIOXGuxYJcE2wYQm5pUIyhqTSw1kTEx76upnL dt9FqqTF9FlzK7JSfrBRXo4by1mFsIKQsWVEBhOJnOWsJQDxKG3Xko3hef/HTgb8FHveDf+06RU /D3E9P4ILbasPGbooEkV1l2XIA+fnsdT6g2mnrvrBAMqcwmVKs/dGYOOVETcX8I7cVa1S6YGUZr FS03ZQ8bz2gucxfmp01vtE8jVX5l+ssZdsjHV6X2MioaYGYZ0RVFoPNAXLLfJsnphVlUA31tESq ucf0pVJlrsjA9y+213kUhz6vE9K09fLiLB5WX2RnDIP6Ci7k 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(). The user must provide a shadow stack address and size, this must point to memory mapped for use as a shadow stackby map_shadow_stack() with a 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 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. Please further note that the token consumption done by clone3() is not currently implemented in an atomic fashion, Rick indicated that he would look into fixing this if people are OK with the implementation. 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 Reviewed-by: Kees Cook Tested-by: Kees Cook --- 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 (9): Documentation: userspace-api: Add shadow stack API documentation selftests: Provide helper header for shadow stack testing mm: Introduce ARCH_HAS_USER_SHADOW_STACK 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: Explicitly handle child exits due to signals 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 | 41 ++++ arch/x86/Kconfig | 1 + arch/x86/include/asm/shstk.h | 11 +- arch/x86/kernel/process.c | 2 +- arch/x86/kernel/shstk.c | 105 +++++++--- fs/proc/task_mmu.c | 2 +- include/linux/mm.h | 2 +- include/linux/sched/task.h | 13 ++ include/uapi/linux/sched.h | 13 +- kernel/fork.c | 76 ++++++-- mm/Kconfig | 6 + tools/testing/selftests/clone3/clone3.c | 224 ++++++++++++++++++---- tools/testing/selftests/clone3/clone3_selftests.h | 40 +++- tools/testing/selftests/ksft_shstk.h | 63 ++++++ 15 files changed, 513 insertions(+), 87 deletions(-) --- base-commit: 8400291e289ee6b2bf9779ff1c83a291501f017b change-id: 20231019-clone3-shadow-stack-15d40d2bf536 Best regards,