title: blk-mq: fix IO hang from sbitmap wakeup race
description: In the Linux kernel, the following vulnerability has been resolved:
blk-mq: fix IO hang from sbitmap wakeup race
In blk_mq_mark_tag_wait(), __add_wait_queue() may be re-ordered
with the following blk_mq_get_driver_tag() in case of getting driver
tag failure.
Then in __sbitmap_queue_wake_up(), waitqueue_active() may not observe
the added waiter in blk_mq_mark_tag_wait() and wake up nothing, meantime
blk_mq_mark_tag_wait() can't get driver tag successfully.
This issue can be reproduced by running the following test in loop, and
fio hang can be observed in < 30min when running it on my test VM
in laptop.
modprobe -r scsi_debug
modprobe scsi_debug delay=0 dev_size_mb=4096 max_queue=1 host_max_queue=1 submit_queues=4
dev=`ls -d /sys/bus/pseudo/drivers/scsi_debug/adapter*/host*/target*/*/block/* | head -1 | xargs basename`
fio --filename=/dev/"$dev" --direct=1 --rw=randrw --bs=4k --iodepth=1 \
--runtime=100 --numjobs=40 --time_based --name=test \
--ioengine=libaio
Fix the issue by adding one explicit barrier in blk_mq_mark_tag_wait(), which
is just fine in case of running out of tag.
affected:
{
product: Linux
vendor: Linux
defaultStatus: unaffected
repo: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
versions:
version: 1da177e4c3f4, lessThan: 9525b38180e2, status: affected, versionType: git
version: 1da177e4c3f4, lessThan: ecd7744a1446, status: affected, versionType: git
version: 1da177e4c3f4, lessThan: 7610ba131925, status: affected, versionType: git
version: 1da177e4c3f4, lessThan: 89e0e66682e1, status: affected, versionType: git
version: 1da177e4c3f4, lessThan: 1d9c777d3e70, status: affected, versionType: git
version: 1da177e4c3f4, lessThan: 6d8b01624a25, status: affected, versionType: git
version: 1da177e4c3f4, lessThan: f1bc0d8163f8, status: affected, versionType: git
version: 1da177e4c3f4, lessThan: 5266caaf5660, status: affected, versionType: git
}
{
product: Linux
vendor: Linux
defaultStatus: affected
repo: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
versions:
version: 4.19.307, lessThanOrEqual: 4.19.*, status: unaffected, versionType: custom
version: 5.4.269, lessThanOrEqual: 5.4.*, status: unaffected, versionType: custom
version: 5.10.210, lessThanOrEqual: 5.10.*, status: unaffected, versionType: custom
version: 5.15.149, lessThanOrEqual: 5.15.*, status: unaffected, versionType: custom
version: 6.1.77, lessThanOrEqual: 6.1.*, status: unaffected, versionType: custom
version: 6.6.16, lessThanOrEqual: 6.6.*, status: unaffected, versionType: custom
version: 6.7.4, lessThanOrEqual: 6.7.*, status: unaffected, versionType: custom
version: 6.8, lessThanOrEqual: *, status: unaffected, versionType: original_commit_for_fix
}
