High · published September 16, 2025
In the Linux kernel, the following vulnerability has been resolved:
efivarfs: Fix slab-out-of-bounds in efivarfs_d_compare
Observed on kernel 6.6 (present on master as well):
BUG: KASAN: slab-out-of-bounds in memcmp+0x98/0xd0
Call trace:
kasan_check_range+0xe8/0x190
__asan_loadN+0x1c/0x28
memcmp+0x98/0xd0
efivarfs_d_compare+0x68/0xd8
__d_lookup_rcu_op_compare+0x178/0x218
__d_lookup_rcu+0x1f8/0x228
d_alloc_parallel+0x150/0x648
lookup_open.isra.0+0x5f0/0x8d0
open_last_lookups+0x264/0x828
path_openat+0x130/0x3f8
do_filp_open+0x114/0x248
do_sys_openat2+0x340/0x3c0
__arm64_sys_openat+0x120/0x1a0
If dentry->d_name.len < EFI_VARIABLE_GUID_LEN , 'guid' can become
negative, leadings to oob. The issue can be triggered by parallel
lookups using invalid filename:
T1 T2
lookup_open
->lookup
simple_lookup
d_add
// invalid dentry is added to hash list
lookup_open
d_alloc_parallel
__d_lookup_rcu
__d_lookup_rcu_op_compare
hlist_bl_for_each_entry_rcu
// invalid dentry can be retrieved
->d_compare
efivarfs_d_compare
// oob
Fix it by checking 'guid' before cmp.
| Product | Versions | Fixed in |
|---|---|---|
| linux/linux_kernel | ≥ 3.8.2, < 5.4.298 | 5.4.298 |
| linux/linux_kernel | ≥ 5.5, < 5.10.242 | 5.10.242 |
| linux/linux_kernel | ≥ 5.11, < 5.15.191 | 5.15.191 |
| linux/linux_kernel | ≥ 5.16, < 6.1.150 | 6.1.150 |
| linux/linux_kernel | ≥ 6.2, < 6.6.104 | 6.6.104 |
| linux/linux_kernel | ≥ 6.7, < 6.12.45 | 6.12.45 |
| linux/linux_kernel | ≥ 6.13, < 6.16.5 | 6.16.5 |
| linux/linux_kernel | all versions | — |
| linux/linux_kernel | all versions | — |
| linux/linux_kernel | all versions | — |
| debian/debian_linux | all versions | — |