From: Yu Kuai <yukuai3@xxxxxxxxxx>
blk_mq_free_tags() can be called after blk_mq_init_tags(), while
tags->page_list is still not initialized, causing null-ptr-deref.
Fix this problem by initializing tags->page_list at blk_mq_init_tags(),
meanwhile, also free tags directly from error path because there is no
srcu barrier.
Fixes: ad0d05dbddc1 ("blk-mq: Defer freeing of tags page_list to SRCU callback")
Reported-by: syzbot+5c5d41e80248d610221f@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://lore.kernel.org/all/68d1b079.a70a0220.1b52b.0000.GAE@xxxxxxxxxx/
Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
---
block/blk-mq-tag.c | 9 +++++++++
block/blk-mq.c | 2 --
2 files changed, 9 insertions(+), 2 deletions(-)
diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index a63d21a4aab4..23f7731f19d1 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -569,6 +569,8 @@ struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
tags->nr_tags = total_tags;
tags->nr_reserved_tags = reserved_tags;
spin_lock_init(&tags->lock);
+ INIT_LIST_HEAD(&tags->page_list);
+
if (bt_alloc(&tags->bitmap_tags, depth, round_robin, node))
goto out_free_tags;
if (bt_alloc(&tags->breserved_tags, reserved_tags, round_robin, node))
@@ -606,6 +608,13 @@ void blk_mq_free_tags(struct blk_mq_tag_set *set, struct blk_mq_tags *tags)
{
sbitmap_queue_free(&tags->bitmap_tags);
sbitmap_queue_free(&tags->breserved_tags);
+
+ /* if tags pages is not allocated yet, free tags directly */
+ if (list_empty(&tags->page_list)) {
+ kfree(tags);
+ return;
+ }
+
call_srcu(&set->tags_srcu, &tags->rcu_head, blk_mq_free_tags_callback);
}
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 4ccf11cadf8c..09f579414161 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -3582,8 +3582,6 @@ static int blk_mq_alloc_rqs(struct blk_mq_tag_set *set,
if (node == NUMA_NO_NODE)
node = set->numa_node;
- INIT_LIST_HEAD(&tags->page_list);
-
/*
* rq_size is the size of the request plus driver payload, rounded
* to the cacheline size
--
2.39.2
