bfq: Update cgroup information before merging bio

BugLink: https://bugs.launchpad.net/bugs/1981864
commit ea591cd4eb270393810e7be01feb8fde6a34fbbe upstream.

When the process is migrated to a different cgroup (or in case of
writeback just starts submitting bios associated with a different
cgroup) bfq_merge_bio() can operate with stale cgroup information in
bic. Thus the bio can be merged to a request from a different cgroup or
it can result in merging of bfqqs for different cgroups or bfqqs of
already dead cgroups and causing possible use-after-free issues. Fix the
problem by updating cgroup information in bfq_merge_bio().

CC: stable@vger.kernel.org
Fixes: e21b7a0b9887 ("block, bfq: add full hierarchical scheduling and cgroups support")
Tested-by: "yukuai (C)" <yukuai3@huawei.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220401102752.8599-4-jack@suse.cz
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index d32d4efba9684d7c66b14a043c2006c9d32b3b08..e1183596de0676058f8dcd924054d3ca5fe8ae66 100644 (file)
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -2335,10 +2335,17 @@ static bool bfq_bio_merge(struct request_queue *q, struct bio *bio,
 
        spin_lock_irq(&bfqd->lock);
 
-       if (bic)
+       if (bic) {
+               /*
+                * Make sure cgroup info is uptodate for current process before
+                * considering the merge.
+                */
+               bfq_bic_update_cgroup(bic, bio);
+
                bfqd->bio_bfqq = bic_to_bfqq(bic, op_is_sync(bio->bi_opf));
-       else
+       } else {
                bfqd->bio_bfqq = NULL;
+       }
        bfqd->bio_bic = bic;
 
        ret = blk_mq_sched_try_merge(q, bio, nr_segs, &free);