ext4: validate EA inode i_nlink in ext4_xattr_inode_iget

Validate EA inode state in ext4_xattr_inode_iget() to reject corrupted
EA inodes early, before they trigger WARN_ONCE in
ext4_xattr_inode_update_ref().

When a corrupted ext4 image has an EA inode with inconsistent i_nlink
and ref_count values (e.g. i_nlink=65535), the code currently allows it
through and later hits WARN_ONCE when ref_count transitions cross the
0/1 boundary.  This is better handled as an early sanity check that
returns -EFSCORRUPTED, consistent with how ext4 treats other on-disk
corruption.

Since ext4_xattr_inode_iget() resolves references from active xattr
entries, the target EA inode must be in active state (i_nlink=1,
ref_count>0).  Reject any inode that does not satisfy this.

Reported-by: syzbot+76916a45d2294b551fd9@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=76916a45d2294b551fd9
Fixes: dec214d00e0d ("ext4: xattr inode deduplication")
Signed-off-by: Yun Zhou <yun.zhou@windriver.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/20260724100255.144768-1-yun.zhou@windriver.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

0 files changed, 0 insertions, 0 deletions