blk-mq: fix use-after-free in blk_mq_free_tag_set()

tags is freed in blk_mq_free_rq_map() and should not be used after that.
The problem doesn't manifest if CONFIG_CPUMASK_OFFSTACK is false because
free_cpumask_var() is nop.

tags->cpumask is allocated in blk_mq_init_tags() so it's natural to
free cpumask in its counter part, blk_mq_free_tags().

Fixes: f26cdc8536ad ("blk-mq: Shared tag enhancements")
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Cc: Keith Busch <keith.busch@intel.com>
Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index ed96474d75cb62fb261526736727c67ea2238d46..ec2d11915142a8f9b7a49e839e41a2f54a55aa09 100644 (file)
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -641,6 +641,7 @@ void blk_mq_free_tags(struct blk_mq_tags *tags)
 {
        bt_free(&tags->bitmap_tags);
        bt_free(&tags->breserved_tags);
+       free_cpumask_var(tags->cpumask);
        kfree(tags);
 }
 

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 7785ae96267a197926c700f74bcd6524892a8c01..85f014327342efc775c31833a52f531b69a66329 100644 (file)
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2296,10 +2296,8 @@ void blk_mq_free_tag_set(struct blk_mq_tag_set *set)
        int i;
 
        for (i = 0; i < set->nr_hw_queues; i++) {
-               if (set->tags[i]) {
+               if (set->tags[i])
                        blk_mq_free_rq_map(set, set->tags[i], i);
-                       free_cpumask_var(set->tags[i]->cpumask);
-               }
        }
 
        kfree(set->tags);