In the Linux kernel, the following vulnerability has been resolved:
btrfs: only release the dirty pages io tree after successful writes
[WARNING]
With extra warning on dirty extent buffers at umount (aka, the next
patch in the series), test case generic/388 can trigger the following
warning about dirty extent buffers at unmount time:
BTRFS critical (device dm-2 state E): emergency shutdown
BTRFS error (device dm-2 state E): error while writing out transaction: -30
BTRFS warning (device dm-2 state E): Skipping commit of aborted transaction.
BTRFS error (device dm-2 state EA): Transaction 9 aborted (error -30)
BTRFS: error (device dm-2 state EA) in cleanup_transaction:2068: errno=-30 Readonly filesystem
BTRFS info (device dm-2 state EA): forced readonly
BTRFS info (device dm-2 state EA): last unmount of filesystem 4fbf2e15-f941-49a0-bc7c-716315d2777c
------------[ cut here ]------------
WARNING: disk-io.c:3311 at invalidate_and_check_btree_folios+0xfd/0x1ca [btrfs], CPU#8: umount/914368
CPU: 8 UID: 0 PID: 914368 Comm: umount Tainted: G OE 7.1.0-rc1-custom+ #372 PREEMPT(full) 2de38db8d1deae71fde295430a0ff3ab98ccf596
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS unknown 02/02/2022
RIP: 0010:invalidate_and_check_btree_folios+0xfd/0x1ca [btrfs]
Call Trace:
<TASK>
close_ctree+0x52e/0x574 [btrfs d2f0b1cd330d1287e7a9919d112eadfc0e914efd]
generic_shutdown_super+0x89/0x1a0
kill_anon_super+0x16/0x40
btrfs_kill_super+0x16/0x20 [btrfs d2f0b1cd330d1287e7a9919d112eadfc0e914efd]
deactivate_locked_super+0x2d/0xb0
cleanup_mnt+0xdc/0x140
task_work_run+0x5a/0xa0
exit_to_user_mode_loop+0x123/0x4b0
do_syscall_64+0x243/0x7c0
entry_SYSCALL_64_after_hwframe+0x4b/0x53
</TASK>
---[ end trace 0000000000000000 ]---
BTRFS warning (device dm-2 state EA): unable to release extent buffer 30539776 owner 9 gen 9 refs 2 flags 0x7
BTRFS warning (device dm-2 state EA): unable to release extent buffer 30621696 owner 257 gen 9 refs 2 flags 0x7
BTRFS warning (device dm-2 state EA): unable to release extent buffer 30638080 owner 258 gen 9 refs 2 flags 0x7
BTRFS warning (device dm-2 state EA): unable to release extent buffer 30654464 owner 7 gen 9 refs 2 flags 0x7
BTRFS warning (device dm-2 state EA): unable to release extent buffer 30703616 owner 2 gen 9 refs 2 flags 0x7
BTRFS warning (device dm-2 state EA): unable to release extent buffer 30720000 owner 10 gen 9 refs 2 flags 0x7
BTRFS warning (device dm-2 state EA): unable to release extent buffer 30736384 owner 4 gen 9 refs 2 flags 0x7
BTRFS warning (device dm-2 state EA): unable to release extent buffer 30752768 owner 11 gen 9 refs 2 flags 0x7
I'm using a stripped down version, which seems to trigger the warning
more reliably:
_fsstress_pid=""
workload()
{
dmesg -C
mkfs.btrfs -f -K $dev > /dev/null
echo 1 > /sys/kernel/debug/clear_warn_once
mount $dev $mnt
$fsstress -w -n 1024 -p 4 -d $mnt &
_fsstress_pid=$!
sleep 0
$godown $mnt
pkill --echo -PIPE fsstress > /dev/null
wait $_fsstress_pid
unset _fsstress_pid
umount $mnt
<pre>
if dmesg | grep -q "WARNING"; then
fail
fi
</pre>
}
for (( i = 0; i < $runtime; i++ )); do
echo "=== $i/$runtime ==="
workload
done
[CAUSE]
Inside btrfs_write_and_wait_transaction(), we first try to write all
dirty ebs, then wait for them to finish.
After that we call btrfs_extent_io_tree_release() to free all
extent states from dirty_pages io tree.
However if we hit an error from btrfs_write_marked_extent(), then we
still call btrfs_extent_io_tree_release() to clear that dirty_pages io
tree, which may contain dirty records that we haven't yet submitted.
Furthermore, the later transaction cleanup path will utilize that
dirty_pages io tree to properly cleanup those dirty ebs, but since it's
already empty, no dirty ebs are properly cleaned up, thus will later
trigger the warnings inside invalidate_btree_folios().
---truncated---