From patchwork Sat Oct 5 10:31:27 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Brown X-Patchwork-Id: 13823206 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 5B2A3145A09; Sat, 5 Oct 2024 10:32:39 +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=1728124360; cv=none; b=qumBu0x40MxAbwAWtK28NYxApujTeHl+bVmldlDCZ2d7ow8mjp8domEIV/eBhMaxXqeOtSIBK/9oitkILdrM6H6j2sR+IKibI+HrAlqYgcEaIlb1HyXfF6i74g5FqJm/bFpYqAskKV94NKiuyngH9RgdVfw5D3gynYlKn1fe3/o= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728124360; c=relaxed/simple; bh=XsBBt9+t8yXn9dg+YujCNxrelnkKQB+3nk37zwPXgio=; h=From:Subject:Date:Message-Id:MIME-Version:Content-Type:To:Cc; b=qu49kIbvur9f3EJeVMZ+6+/ji5aowNzqe13fzirTQ0F0Qiiq36YMXrcY0nouflnkAfDo/joAhcxgeTbJYhE+Poi38eQGcw9exvctQiOB9PNdIqEO4LSbqEMlK8GJg5QFuqDiow9zybxQic2YWdSrzSBYhHKWcramJkE+2W1bZzE= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ZYLadirp; 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="ZYLadirp" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 023B2C4CEC2; Sat, 5 Oct 2024 10:32:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1728124359; bh=XsBBt9+t8yXn9dg+YujCNxrelnkKQB+3nk37zwPXgio=; h=From:Subject:Date:To:Cc:From; b=ZYLadirpm9Yhmgb/rMfoHjHmReYjsu1IAwVmoBBpqKXxKFWyQYgMIs0ll0KZahKoK Vy++BE6Efl8VkQetwFJrE4Mu/CFXCAHSb+mUMMkpxSUDNFPu/zb6IWoc4QK1csqXhQ ucZqOldttU+fFezqweKis/ciHaVpzZ6y0cydojcJJ5KIS7DTpKXaaDGm3wjKBpi8rP 5m0NywfVghCS+uZNugp5q5XGl1g+JCUUoaVGOpAOqv8DW2gPi/GV1Cuhy1IAFDeoUp FDVvwzCCxxdia213BhYww7FsNv6gajvDzj8OBi2/I+WJaNVi2Pef4sxWaYrJg35H48 DAZhyCJXaI9+w== From: Mark Brown Subject: [PATCH RFT v11 0/8] fork: Support shadow stacks in clone3() Date: Sat, 05 Oct 2024 11:31:27 +0100 Message-Id: <20241005-clone3-shadow-stack-v11-0-2a6a2bd6d651@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=H4sIAH8VAWcC/3XSzU7DMAwH8FeZcqYodr534sQDIG6IQ5M4W7WpR e1UQNPenawItSjtMY78S/yXr2ygvqGB7XdX1tPYDE3X5gPAw46FY90eqGpiLjDkKICDq8K5a0l Uw7GO3Wc1XOpwqkBFySP6pIRmufOjp9R8Tewbe3l+Ze+5eGyGS9d/T0+NMF39oihW0REqXkWrT eQ++5E/nahv6fzY9YcJHHFGAOQ6ghnxGkSy2gIoVSBigSBfR0RGauMtRUFYh1AgconYdURmxHq 0KZFM2ugCUX+I5Mg3MlEZEYhBO+UsSV8gekb0VrA6I47IGCs8JO8KxMyIEbCOmHsmTgkk8slDL BA7I5ZvZGIzwuuQhAl1AlkG6xbIxvKN7j6Oxmhkck5qWSDAFwpuzAP8/hdN1jjjnZT/N+V2u/0 AyBW+PCwDAAA= 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=7132; i=broonie@kernel.org; h=from:subject:message-id; bh=XsBBt9+t8yXn9dg+YujCNxrelnkKQB+3nk37zwPXgio=; b=owEBbQGS/pANAwAKASTWi3JdVIfQAcsmYgBnARW6SaMiqGrNXX3HwfhzMLwyAq+Qowfw1M4Z1mrC EgUwlomJATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCZwEVugAKCRAk1otyXVSH0EuDB/ 9I8leHuMuB7CaAF5elsrJPlgNbaSqa+Ud2vWsMgRwB+HfZtGXThJBQPRqKq+N2a8MNm+Itbc+3GplJ xXJmnDYfg8rwflE8P3mUDqxdB4106lYbJDbSXBVS9R6dkVRrwrjlrVtP+cy4mQbLjigGbqFDvBzHXy Kgt92DCAYILn4jy35I2MNNJCiCt7dI39zDd5A5fbbpujRbMpkqIfnyFZh902pzeWPbNpoJXalPvWZl dePy7RaZFlo7P3kcT8o1nTAp79YiiR+sCd64/ehd07ki2O+fpIVEBJ8mwfPUFziQATdGmsGFv7tq0W xsYRO4FPwEOEctFAVYwvfOPAVhOAdM 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 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 | 41 ++++ 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, 632 insertions(+), 81 deletions(-) --- base-commit: d17cd7b7cc92d37ee8b2df8f975fc859a261f4dc change-id: 20231019-clone3-shadow-stack-15d40d2bf536 Best regards,