CVE-2026-63814: f2fs: validate ACL entry sizes in f2fs_acl_from_disk()

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

f2fs: validate ACL entry sizes in f2fsaclfromdisk()

f2fsaclcount() only validates the aggregate ACL xattr length. A malformed ACL can still place ACLUSER or ACLGROUP in a slot that only contains struct f2fsaclentryshort bytes, and f2fsaclfromdisk() then reads entry->eid before verifying that a full entry fits.

Require a short entry before reading etag and eperm, and require a full entry before reading eid for ACLUSER and ACLGROUP. 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 f2fsgetacl+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: dumpstacklvl+0x66/0xa0 (?:?) printreport+0xce/0x630 (?:?) f2fsgetacl+0x6fb/0x7e0 (fs/f2fs/acl.c:169) srsoaliasreturnthunk+0x5/0xfbef5 (?:?) virtaddrvalid+0x224/0x430 (?:?) kasanreport+0xe0/0x110 (?:?) f2fsgetacl+0x5/0x7e0 (fs/f2fs/acl.c:169) getacl+0x281/0x380 (?:?) vfsgetacl+0x10b/0x190 (?:?) dogetacl+0x2a/0x410 (?:?) dogetacl+0x9/0x410 (?:?) dogetxattr+0xe8/0x260 (?:?) filenamegetxattr+0xd1/0x140 (?:?) dogetname+0x2d/0x2d0 (?:?) pathgetxattrat+0x16c/0x200 (?:?) lockrelease+0xc8/0x290 (?:?) cgroupupdatefrozen+0x9d/0x320 (?:?) lockdephardirqsonprepare+0xea/0x1a0 (?:?) tracehardirqson+0x1a/0x170 (?:?) rawspinunlockirq+0x28/0x50 (?:?) dosyscall64+0x115/0x6a0 (arch/x86/entry/syscall64.c:87) entrySYSCALL64afterhwframe+0x77/0x7f (?:?)