Re: [PATCH] block: blk-mq: fix UAF in blk_mq_tagset_busy_iter

[Bart Van Assche <bvanassche@acm.org>]

On 4/29/26 9:28 PM, l1za0.sec@gmail.com wrote:
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index d626d32f6e57..4357625a512d 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -4738,6 +4738,7 @@ static int blk_mq_realloc_tag_set_tags(struct blk_mq_tag_set *set,
>   				       int new_nr_hw_queues)
>   {
>   	struct blk_mq_tags **new_tags;
> +	struct blk_mq_tags **old_tags;
>   	int i;
>   
>   	if (set->nr_hw_queues >= new_nr_hw_queues)
> @@ -4751,8 +4752,10 @@ static int blk_mq_realloc_tag_set_tags(struct blk_mq_tag_set *set,
>   	if (set->tags)
>   		memcpy(new_tags, set->tags, set->nr_hw_queues *
>   		       sizeof(*set->tags));
> -	kfree(set->tags);
> +	old_tags = set->tags;
>   	set->tags = new_tags;
> +	synchronize_srcu(&set->tags_srcu);
> +	kfree(old_tags);
>   
>   	for (i = set->nr_hw_queues; i < new_nr_hw_queues; i++) {
>   		if (!__blk_mq_alloc_map_and_rqs(set, i)) {

The function blk_mq_realloc_tag_set_tags() no longer exists.

> base-commit: 7d0a66e4bb9081d75c82ec4957c50034cb0ea449

That commit is too old. It's description is as follows: "Merge tag
'timers_urgent_for_v6.18_rc8' of git://git.kernel.org/pub/scm/linux/
kernel/git/tip/tip". Please develop block layer fixes against the
for-next branch of this kernel tree:
https://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux.git/

Thanks,

Bart.