CVE-2026-63814

In the Linux kernel, the following vulnerability has been resolved:

f2fs: validate ACL entry sizes in f2fs_acl_from_disk()

f2fs_acl_count() only validates the aggregate ACL xattr length. A

malformed ACL can still place ACL_USER or ACL_GROUP in a slot that only

contains struct f2fs_acl_entry_short bytes, and f2fs_acl_from_disk()

then reads entry->e_id before verifying that a full entry fits.

Require a short entry before reading e_tag and e_perm, and require a

full entry before reading e_id for ACL_USER and ACL_GROUP. Return

-EFSCORRUPTED from these new truncated-entry checks, while keeping the

pre-existing -EINVAL paths unchanged.

Validation reproduced this kernel report:

KASAN slab-out-of-bounds in __f2fs_get_acl+0x6fb/0x7e0

RIP: 0033:0x7f4b835ea7aa

The buggy address belongs to the object at ffff888114589960 which belongs

to the cache kmalloc-8 of size 8

The buggy address is located 0 bytes to the right of allocated 8-byte

region [ffff888114589960, ffff888114589968)

Read of size 4

Call trace:

dump_stack_lvl+0x66/0xa0 (?:?)

print_report+0xce/0x630 (?:?)

__f2fs_get_acl+0x6fb/0x7e0 (fs/f2fs/acl.c:169)

srso_alias_return_thunk+0x5/0xfbef5 (?:?)

__virt_addr_valid+0x224/0x430 (?:?)

kasan_report+0xe0/0x110 (?:?)

__f2fs_get_acl+0x5/0x7e0 (fs/f2fs/acl.c:169)

__get_acl+0x281/0x380 (?:?)

vfs_get_acl+0x10b/0x190 (?:?)

do_get_acl+0x2a/0x410 (?:?)

do_get_acl+0x9/0x410 (?:?)

do_getxattr+0xe8/0x260 (?:?)

filename_getxattr+0xd1/0x140 (?:?)

do_getname+0x2d/0x2d0 (?:?)

path_getxattrat+0x16c/0x200 (?:?)

lock_release+0xc8/0x290 (?:?)

cgroup_update_frozen+0x9d/0x320 (?:?)

lockdep_hardirqs_on_prepare+0xea/0x1a0 (?:?)

trace_hardirqs_on+0x1a/0x170 (?:?)

_raw_spin_unlock_irq+0x28/0x50 (?:?)

do_syscall_64+0x115/0x6a0 (arch/x86/entry/syscall_64.c:87)

entry_SYSCALL_64_after_hwframe+0x77/0x7f (?:?)