block, bfq: fix UAF problem in bfqg_stats_init()

In bfq_pd_alloc(), the function bfqg_stats_init() init bfqg. If
blkg_rwstat_init() init bfqg_stats->bytes successful and init
bfqg_stats->ios failed, bfqg_stats_init() return failed, bfqg will
be freed. But blkg_rwstat->cpu_cnt is not deleted from the list of
percpu_counters. If we traverse the list of percpu_counters, It will
have UAF problem.

we should use blkg_rwstat_exit() to cleanup bfqg_stats bytes in the
above scenario.

Fixes: commit fd41e60331b ("bfq-iosched: stop using blkg->stat_bytes and ->stat_ios")
Signed-off-by: Zheng Liang <zhengliang6@huawei.com>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20211018024225.1493938-1-zhengliang6@huawei.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c
index 882ec4b..24a5c53 100644 (file)
--- a/block/bfq-cgroup.c
+++ b/block/bfq-cgroup.c
@@ -463,7 +463,7 @@ static int bfqg_stats_init(struct bfqg_stats *stats, gfp_t gfp)
 {
        if (blkg_rwstat_init(&stats->bytes, gfp) ||
            blkg_rwstat_init(&stats->ios, gfp))
-               return -ENOMEM;
+               goto error;
 
 #ifdef CONFIG_BFQ_CGROUP_DEBUG
        if (blkg_rwstat_init(&stats->merged, gfp) ||
@@ -476,13 +476,15 @@ static int bfqg_stats_init(struct bfqg_stats *stats, gfp_t gfp)
            bfq_stat_init(&stats->dequeue, gfp) ||
            bfq_stat_init(&stats->group_wait_time, gfp) ||
            bfq_stat_init(&stats->idle_time, gfp) ||
-           bfq_stat_init(&stats->empty_time, gfp)) {
-               bfqg_stats_exit(stats);
-               return -ENOMEM;
-       }
+           bfq_stat_init(&stats->empty_time, gfp))
+               goto error;
 #endif
 
        return 0;
+
+error:
+       bfqg_stats_exit(stats);
+       return -ENOMEM;
 }
 
 static struct bfq_group_data *cpd_to_bfqgd(struct blkcg_policy_data *cpd)