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blk-mq: fix null-ptr-deref in blk_mq_free_tags() from error path 

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: ad0d05dbdd ("blk-mq: Defer freeing of tags page_list to SRCU callback")
Reported-by: syzbot+5c5d41e80248d610221f@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/68d1b079.a70a0220.1b52b.0000.GAE@google.com/
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Yu Kuai 2025-09-23 15:01:01 +08:00 committed by Jens Axboe
parent fea55691ac
commit 670bfe6838
2 changed files with 9 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
block/blk-mq-tag.c
View File

@ -566,6 +566,8 @@ struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
tags->nr_tags = total_tags; tags->nr_tags = total_tags;
tags->nr_reserved_tags = reserved_tags; tags->nr_reserved_tags = reserved_tags;
spin_lock_init(&tags->lock); spin_lock_init(&tags->lock);
INIT_LIST_HEAD(&tags->page_list);
if (bt_alloc(&tags->bitmap_tags, depth, round_robin, node)) if (bt_alloc(&tags->bitmap_tags, depth, round_robin, node))
goto out_free_tags; goto out_free_tags;
if (bt_alloc(&tags->breserved_tags, reserved_tags, round_robin, node)) if (bt_alloc(&tags->breserved_tags, reserved_tags, round_robin, node))
@ -603,6 +605,13 @@ 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->bitmap_tags);
sbitmap_queue_free(&tags->breserved_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); call_srcu(&set->tags_srcu, &tags->rcu_head, blk_mq_free_tags_callback);
} }

2
block/blk-mq.c
View File

@ -3582,8 +3582,6 @@ static int blk_mq_alloc_rqs(struct blk_mq_tag_set *set,
if (node == NUMA_NO_NODE) if (node == NUMA_NO_NODE)
node = set->numa_node; node = set->numa_node;
INIT_LIST_HEAD(&tags->page_list);
/* /*
* rq_size is the size of the request plus driver payload, rounded * rq_size is the size of the request plus driver payload, rounded
* to the cacheline size * to the cacheline size