In the Linux kernel, the following vulnerability has been resolved:
xfs: fix cursor and pointer handling when recovering iunlink buckets
LOLLM pointed out a bug in xlog_recover_iunlink_bucket:
1. We don’t null out prev_ip after releasing it, which can lead to UAF
problems if the inodegc flush call in the loop fails.
at which point I noticed even more bugs:
2. If the inodegc flush inside the loop fails, we also leak @ip.
3. We set prev_agino to agino having already advanced agino, which
results in inodes with i_prev_unlinked set to itself.
4. If we exit the bottom of the loop with prev_ip set, then prev_ip
aliases ip and we also set its i_prev_unlinked to itself.
Bugs 3 and 4 introduce loops into the unlinked list, though these loops
don’t surface because we immediately flush each unlinked inode after
loading it.
Fix all of these issues.
