ocfs2: validate inline xattr size and entry count in ocfs2_xattr_ibody_list
Add comprehensive validation of inline xattr metadata in
ocfs2_xattr_ibody_list() to prevent out-of-bounds access and
use-after-free bugs when processing corrupted inline xattrs.
The patch adds two critical validations:
1. Validates i_xattr_inline_size before use:
- Ensures it does not exceed block size
- Ensures it is at least large enough for xattr header
- Prevents pointer arithmetic with corrupted size values that could
point outside the inode block
2. Validates xattr entry count (xh_count):
- Calculates maximum entries that can fit in the inline space
- Rejects counts that exceed this limit
- Prevents out-of-bounds array access in subsequent code
Without these checks, a corrupted filesystem with invalid inline xattr
metadata can cause the code to access memory beyond the allocated space.
For example:
- A corrupted i_xattr_inline_size of 0 would cause header pointer
calculation to point past the end of the block
- A corrupted xh_count of 22 with inline_size of 256 would cause
array access 7 entries beyond the 15 that actually fit (the syzbot
reproducer used xh_count of 20041), leading to use-after-free when
accessing freed memory pages
The validation uses the correct inline_size (from di->i_xattr_inline_size)
rather than block size, ensuring accurate bounds checking for inline
xattrs specifically.
Link: https://lkml.kernel.org/r/20251120041145.33176-1-kartikey406@gmail.com
Link: https://lore.kernel.org/all/20251111073831.2027072-1-kartikey406@gmail.com/ [v1]
Link: https://lore.kernel.org/all/20251117063217.5690-1-kartikey406@gmail.com/ [v2]
Link: https://lore.kernel.org/all/20251117114224.12948-1-kartikey406@gmail.com/ [v3]
Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
Reported-by: syzbot+ab0ad25088673470d2d9@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=ab0ad25088673470d2d9
Tested-by: syzbot+ab0ad25088673470d2d9@syzkaller.appspotmail.com
Suggested-by: Heming Zhao <heming.zhao@suse.com>
Reviewed-by: Heming Zhao <heming.zhao@suse.com>
Acked-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Changwei Ge <gechangwei@live.cn>
Cc: Jun Piao <piaojun@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
diff --git a/fs/ocfs2/xattr.c b/fs/ocfs2/xattr.c
index 73c028f..610f1a8 100644
--- a/fs/ocfs2/xattr.c
+++ b/fs/ocfs2/xattr.c
@@ -971,13 +971,39 @@ static int ocfs2_xattr_ibody_list(struct inode *inode,
struct ocfs2_xattr_header *header = NULL;
struct ocfs2_inode_info *oi = OCFS2_I(inode);
int ret = 0;
+ u16 xattr_count;
+ size_t max_entries;
+ u16 inline_size;
if (!(oi->ip_dyn_features & OCFS2_INLINE_XATTR_FL))
return ret;
+ inline_size = le16_to_cpu(di->i_xattr_inline_size);
+
+ /* Validate inline size is reasonable */
+ if (inline_size > inode->i_sb->s_blocksize ||
+ inline_size < sizeof(struct ocfs2_xattr_header)) {
+ ocfs2_error(inode->i_sb,
+ "Invalid xattr inline size %u in inode %llu\n",
+ inline_size,
+ (unsigned long long)OCFS2_I(inode)->ip_blkno);
+ return -EFSCORRUPTED;
+ }
+
header = (struct ocfs2_xattr_header *)
- ((void *)di + inode->i_sb->s_blocksize -
- le16_to_cpu(di->i_xattr_inline_size));
+ ((void *)di + inode->i_sb->s_blocksize - inline_size);
+
+ xattr_count = le16_to_cpu(header->xh_count);
+ max_entries = (inline_size - sizeof(struct ocfs2_xattr_header)) /
+ sizeof(struct ocfs2_xattr_entry);
+
+ if (xattr_count > max_entries) {
+ ocfs2_error(inode->i_sb,
+ "xattr entry count %u exceeds maximum %zu in inode %llu\n",
+ xattr_count, max_entries,
+ (unsigned long long)OCFS2_I(inode)->ip_blkno);
+ return -EFSCORRUPTED;
+ }
ret = ocfs2_xattr_list_entries(inode, header, buffer, buffer_size);
