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 for malformed on-disk ACL blobs so corrupted ACL xattrs
are reported as filesystem corruption instead of generic invalid
arguments.
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 (?:?)
Fixes: af48b85b8cd3 ("f2fs: add xattr and acl functionalities")
Assisted-by: Codex:gpt-5.5
Signed-off-by: Zhang Cen <[email protected]>
---
Changes in v2:
- Wrap the new ACL entry-size checks in unlikely().
- Return -EFSCORRUPTED for malformed on-disk ACL blobs.
fs/f2fs/acl.c | 17 ++++++++++++-----
1 file changed, 12 insertions(+), 5 deletions(-)
diff --git a/fs/f2fs/acl.c b/fs/f2fs/acl.c
index fa8d81a30fb91..e62ce979be0b7 100644
--- a/fs/f2fs/acl.c
+++ b/fs/f2fs/acl.c
@@ -53,14 +53,14 @@ static struct posix_acl *f2fs_acl_from_disk(const char
*value, size_t size)
const char *end = value + size;
if (size < sizeof(struct f2fs_acl_header))
- return ERR_PTR(-EINVAL);
+ return ERR_PTR(-EFSCORRUPTED);
if (hdr->a_version != cpu_to_le32(F2FS_ACL_VERSION))
- return ERR_PTR(-EINVAL);
+ return ERR_PTR(-EFSCORRUPTED);
count = f2fs_acl_count(size);
if (count < 0)
- return ERR_PTR(-EINVAL);
+ return ERR_PTR(-EFSCORRUPTED);
if (count == 0)
return NULL;
@@ -70,7 +70,8 @@ static struct posix_acl *f2fs_acl_from_disk(const char
*value, size_t size)
for (i = 0; i < count; i++) {
- if ((char *)entry > end)
+ if (unlikely((char *)entry +
+ sizeof(struct f2fs_acl_entry_short) > end))
goto fail;
acl->a_entries[i].e_tag = le16_to_cpu(entry->e_tag);
@@ -86,6 +87,9 @@ static struct posix_acl *f2fs_acl_from_disk(const char
*value, size_t size)
break;
case ACL_USER:
+ if (unlikely((char *)entry +
+ sizeof(struct f2fs_acl_entry) > end))
+ goto fail;
acl->a_entries[i].e_uid =
make_kuid(&init_user_ns,
le32_to_cpu(entry->e_id));
@@ -93,6 +97,9 @@ static struct posix_acl *f2fs_acl_from_disk(const char
*value, size_t size)
sizeof(struct f2fs_acl_entry));
break;
case ACL_GROUP:
+ if (unlikely((char *)entry +
+ sizeof(struct f2fs_acl_entry) > end))
+ goto fail;
acl->a_entries[i].e_gid =
make_kgid(&init_user_ns,
le32_to_cpu(entry->e_id));
@@ -108,7 +115,7 @@ static struct posix_acl *f2fs_acl_from_disk(const char
*value, size_t size)
return acl;
fail:
posix_acl_release(acl);
- return ERR_PTR(-EINVAL);
+ return ERR_PTR(-EFSCORRUPTED);
}
static void *f2fs_acl_to_disk(struct f2fs_sb_info *sbi,
--
2.43.0
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