In the Linux kernel, the following vulnerability has been resolved:
efivarfs: Fix slab-out-of-bounds in efivarfsdcompare
Observed on kernel 6.6 (present on master as well):
BUG: KASAN: slab-out-of-bounds in memcmp+0x98/0xd0 Call trace: kasancheckrange+0xe8/0x190 _asanloadN+0x1c/0x28 memcmp+0x98/0xd0 efivarfsdcompare+0x68/0xd8 _dlookuprcuopcompare+0x178/0x218 _dlookuprcu+0x1f8/0x228 dallocparallel+0x150/0x648 lookupopen.isra.0+0x5f0/0x8d0 openlastlookups+0x264/0x828 pathopenat+0x130/0x3f8 dofilpopen+0x114/0x248 dosysopenat2+0x340/0x3c0 _arm64sys_openat+0x120/0x1a0
If dentry->dname.len < EFIVARIABLEGUIDLEN , 'guid' can become negative, leadings to oob. The issue can be triggered by parallel lookups using invalid filename:
T1 T2 lookupopen ->lookup simplelookup 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.