In the Linux kernel, the following vulnerability has been resolved:
erofs: fix use-after-free on sbi->sync_decompress
z_erofs_decompress_kickoff() can race with filesystem unmount, causing
a use-after-free on sbi->sync_decompress.
When I/O completes, z_erofs_endio() calls z_erofs_decompress_kickoff()
to queue z_erofs_decompressqueue_work() asynchronously. Then, after all
folios are unlocked, unmount workflow can proceed and sbi will be freed
before accessing to sbi->sync_decompress.
Thread (unmount) I/O completion kworker
queue_work
z_erofs_decompressqueue_work
(all folios are unlocked)
cleanup_mnt
..
erofs_kill_sb
erofs_sb_free
kfree(sbi)
access sbi->sync_decompress // UAF!!