From e474ac24a79211f83e214d856630829f77363459 Mon Sep 17 00:00:00 2001 From: Leon Hwang Date: Wed, 15 Jul 2026 21:12:58 +0800 Subject: [PATCH] mm/mseal: fix mseal documentation for 32-bit kernels MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit mseal.o is built only for 64-bit kernels, so 32-bit kernels fall back to sys_ni_syscall() and return -ENOSYS rather than -EPERM. Drop architecture description in mseal.rst, since the arch feature doc has the latest state of mseal for each architecture. Fix the CONFIG_MSEAL_SYSTEM_MAPPINGS typo in init/Kconfig. Link: https://lore.kernel.org/20260715131258.55499-1-leon.hwang@linux.dev Signed-off-by: Leon Hwang Acked-by: Lance Yang Cc: Alice Ryhl Cc: Anand Moon Cc: Doug Anderson Cc: Gary Guo Cc: Jann Horn Cc: Jonathan Corbet Cc: Leon Hwang Cc: Liam R. Howlett Cc: Lorenzo Stoakes Cc: Miguel Ojeda Cc: Nathan Chancellor Cc: Pedro Falcato Cc: Peter Zijlstra Cc: Randy Dunlap Cc: Thomas Weißschuh Cc: Vlastimil Babka Signed-off-by: Andrew Morton --- Documentation/userspace-api/mseal.rst | 14 ++++++-------- init/Kconfig | 2 +- 2 files changed, 7 insertions(+), 9 deletions(-) diff --git a/Documentation/userspace-api/mseal.rst b/Documentation/userspace-api/mseal.rst index ea9b11a0bd89..c039d782f9f5 100644 --- a/Documentation/userspace-api/mseal.rst +++ b/Documentation/userspace-api/mseal.rst @@ -50,8 +50,8 @@ mseal syscall signature * The start address (``addr``) is not allocated. * The end address (``addr`` + ``len``) is not allocated. * A gap (unallocated memory) between start and end address. - - **-EPERM**: - * sealing is supported only on 64-bit CPUs, 32-bit is not supported. + - **-ENOSYS**: + * The kernel does not implement ``mseal()``. **Note about error return**: - For above error cases, users can expect the given memory range is @@ -62,7 +62,8 @@ mseal syscall signature memory range could happen. However, those cases should be rare. **Architecture support**: - mseal only works on 64-bit CPUs, not 32-bit CPUs. + mseal is built only for 64-bit kernels. 32-bit kernels return + ``-ENOSYS``. **Idempotent**: users can call mseal multiple times. mseal on an already sealed memory @@ -131,11 +132,11 @@ Use cases - Chrome browser: protect some security sensitive data structures. - System mappings: - The system mappings are created by the kernel and includes vdso, vvar, + The system mappings are created by the kernel and include vdso, vvar, vvar_vclock, vectors (arm compat-mode), sigpage (arm compat-mode), uprobes. Those system mappings are readonly only or execute only, memory sealing can - protect them from ever changing to writable or unmmap/remapped as different + protect them from ever changing to writable or unmapped/remapped as different attributes. This is useful to mitigate memory corruption issues where a corrupted pointer is passed to a memory management system. @@ -143,9 +144,6 @@ Use cases the CONFIG_MSEAL_SYSTEM_MAPPINGS seals all system mappings of this architecture. - The following architectures currently support this feature: x86-64, arm64, - loongarch and s390. - WARNING: This feature breaks programs which rely on relocating or unmapping system mappings. Known broken software at the time of writing includes CHECKPOINT_RESTORE, UML, gVisor, rr. Therefore diff --git a/init/Kconfig b/init/Kconfig index c24f345f794b..13cb6fdd9c37 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -2123,7 +2123,7 @@ config ARCH_SUPPORTS_MSEAL_SYSTEM_MAPPINGS from a kernel perspective. After the architecture enables this, a distribution can set - CONFIG_MSEAL_SYSTEM_MAPPING to manage access to the feature. + CONFIG_MSEAL_SYSTEM_MAPPINGS to manage access to the feature. For complete descriptions of memory sealing, please see Documentation/userspace-api/mseal.rst