6.6-stable review patch. If anyone has any objections, please let me know.
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From: Li Nan linan122@huawei.com
[ Upstream commit a6358f8cf64850f3f27857b8ed8c1b08cfc4685c ]
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.
Fixes: da27a24383b2 ("efivarfs: guid part of filenames are case-insensitive") Signed-off-by: Li Nan linan122@huawei.com Signed-off-by: Wu Guanghao wuguanghao3@huawei.com Signed-off-by: Ard Biesheuvel ardb@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- fs/efivarfs/super.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/fs/efivarfs/super.c b/fs/efivarfs/super.c index 586c5709dfb55..34438981ddd80 100644 --- a/fs/efivarfs/super.c +++ b/fs/efivarfs/super.c @@ -90,6 +90,10 @@ static int efivarfs_d_compare(const struct dentry *dentry, { int guid = len - EFI_VARIABLE_GUID_LEN;
+ /* Parallel lookups may produce a temporary invalid filename */ + if (guid <= 0) + return 1; + if (name->len != len) return 1;