bfq: Make sure bfqg for which we are queueing requests is online

Bios queued into BFQ IO scheduler can be associated with a cgroup that
was already offlined. This may then cause insertion of this bfq_group
into a service tree. But this bfq_group will get freed as soon as last
bio associated with it is completed leading to use after free issues for
service tree users. Fix the problem by making sure we always operate on
online bfq_group. If the bfq_group associated with the bio is not
online, we pick the first online parent.

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/20220401102752.8599-9-jack@suse.cz
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c
index 32d2c2a47480f7f9e74f953c2f431066db3d9791..09574af835662ff1bf998fbd6dcf0df6b53c5b68 100644 (file)
--- a/block/bfq-cgroup.c
+++ b/block/bfq-cgroup.c
@@ -612,10 +612,19 @@ static void bfq_link_bfqg(struct bfq_data *bfqd, struct bfq_group *bfqg)
 struct bfq_group *bfq_bio_bfqg(struct bfq_data *bfqd, struct bio *bio)
 {
        struct blkcg_gq *blkg = bio->bi_blkg;
+       struct bfq_group *bfqg;
 
-       if (!blkg)
-               return bfqd->root_group;
-       return blkg_to_bfqg(blkg);
+       while (blkg) {
+               bfqg = blkg_to_bfqg(blkg);
+               if (bfqg->online) {
+                       bio_associate_blkg_from_css(bio, &blkg->blkcg->css);
+                       return bfqg;
+               }
+               blkg = blkg->parent;
+       }
+       bio_associate_blkg_from_css(bio,
+                               &bfqg_to_blkg(bfqd->root_group)->blkcg->css);
+       return bfqd->root_group;
 }
 
 /**