On Wed, Mar 31, 2021 at 11:59:20AM +0200, Jan Kara wrote: > On Wed 31-03-21 11:31:38, Zhang Yi wrote: > > When CONFIG_QUOTA is enabled, if we failed to mount the filesystem due > > to some error happens behind ext4_orphan_cleanup(), it will end up > > triggering a after free issue of super_block. The problem is that > > ext4_orphan_cleanup() will set SB_ACTIVE flag if CONFIG_QUOTA is > > enabled, after we cleanup the truncated inodes, the last iput() will put > > them into the lru list, and these inodes' pages may probably dirty and > > will be write back by the writeback thread, so it could be raced by > > freeing super_block in the error path of mount_bdev(). > > > > After check the setting of SB_ACTIVE flag in ext4_orphan_cleanup(), it > > was used to ensure updating the quota file properly, but evict inode and > > trash data immediately in the last iput does not affect the quotafile, > > so setting the SB_ACTIVE flag seems not required[1]. Fix this issue by > > just remove the SB_ACTIVE setting. > > Thanks for the patch. Let me rephrase the changelog a little: > > When CONFIG_QUOTA is enabled and if we later fail to finish mounting the > filesystem due to some error after ext4_orphan_cleanup(), we may hit use > after free issues. The problem is that ext4_orphan_cleanup() sets SB_ACTIVE > flag and so inodes processed during the orphan cleanup are put to the > superblock's LRU list instead of being immediately destroyed. However the > path handling error recovery after failed ->fill_super() call does not > destroy inodes attached to the superblock and so they are left active in > memory while the superblock is freed. > > Originally, SB_ACTIVE setting was added so that updated quota information > is not destroyed when we drop quota inode references after orphan cleanup. > However VFS does not purge dirty inode pages without SB_ACTIVE flag for many > years already. So just remove the hack with setting SB_ACTIVE flag from > ext4_orphan_cleanup(). > > Also feel free to add: > > Reviewed-by: Jan Kara <jack@xxxxxxx> > > Honza Applied, thanks. - Ted
