diff options
| author | Chris Mason <mason@kernel.org> | 2026-10-29 11:43:25 +0100 |
|---|---|---|
| committer | David Hildenbrand (Arm) <david@kernel.org> | 2026-11-02 11:21:28 +0100 |
| commit | 0237c47ca17005ea41b510c6116f0257dbf84eab (patch) | |
| tree | 6c951fd3362eb2322e0456e094aba921910c0570 /include | |
| parent | d5d861ee303da01e59fdf8e8b2f7096c76e7efd5 (diff) | |
mm/shmem: honour F_SEAL_EXEC when an ACL is set
The owner of a memfd sealed with F_SEAL_EXEC can still change its
execute bits by setting a POSIX access ACL. With CONFIG_TMPFS_POSIX_ACL,
this lets an unprivileged owner make a non-executable memfd executable,
bypassing vm.memfd_noexec=2.
simple_set_acl() updates i_mode directly, bypassing the seal check in
shmem_setattr(). Add shmem_set_acl() to check the resulting mode. Share
the F_SEAL_EXEC check with shmem_setattr() using memfd_check_seals_mode()
in include/linux/memfd.h.
Fix generated by an LLM and sent by Chris Mason in private.
Fixes: 6fd7353829ca ("mm/memfd: add F_SEAL_EXEC")
Cc: stable@vger.kernel.org
Signed-off-by: Chris Mason <mason@kernel.org>
Acked-by: Pedro Falcato <pfalcato@suse.de>
Acked-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
Acked-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Tested-by: Gregory Price (Meta) <gourry@gourry.net>
[ david: use common helper; simplify description ]
Link: https://patch.msgid.link/20261029-fixes_shmem-v4-4-392fc715d8f6@kernel.org
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/memfd.h | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/include/linux/memfd.h b/include/linux/memfd.h index c159e40e3f34..272479317cf1 100644 --- a/include/linux/memfd.h +++ b/include/linux/memfd.h @@ -2,10 +2,19 @@ #ifndef __LINUX_MEMFD_H #define __LINUX_MEMFD_H +#include <linux/fcntl.h> #include <linux/file.h> #define MEMFD_ANON_NAME "[memfd]" +static inline int memfd_check_seals_mode(unsigned int seals, umode_t old_mode, + umode_t new_mode) +{ + if ((seals & F_SEAL_EXEC) && ((old_mode ^ new_mode) & 0111)) + return -EPERM; + return 0; +} + #ifdef CONFIG_MEMFD_CREATE extern long memfd_fcntl(struct file *file, unsigned int cmd, unsigned int arg); struct folio *memfd_alloc_folio(struct file *memfd, pgoff_t idx); |