Re: [PATCH] block: Fix handling of offline queues in blk_mq_alloc_request_hctx()

[Ming Lei <ming.lei@redhat.com>]

On Wed, Jun 15, 2022 at 02:00:04PM -0700, Bart Van Assche wrote:
> This patch prevents that test nvme/004 triggers the following:
> 
> UBSAN: array-index-out-of-bounds in block/blk-mq.h:135:9
> index 512 is out of range for type 'long unsigned int [512]'
> Call Trace:
>  show_stack+0x52/0x58
>  dump_stack_lvl+0x49/0x5e
>  dump_stack+0x10/0x12
>  ubsan_epilogue+0x9/0x3b
>  __ubsan_handle_out_of_bounds.cold+0x44/0x49
>  blk_mq_alloc_request_hctx+0x304/0x310
>  __nvme_submit_sync_cmd+0x70/0x200 [nvme_core]
>  nvmf_connect_io_queue+0x23e/0x2a0 [nvme_fabrics]
>  nvme_loop_connect_io_queues+0x8d/0xb0 [nvme_loop]
>  nvme_loop_create_ctrl+0x58e/0x7d0 [nvme_loop]
>  nvmf_create_ctrl+0x1d7/0x4d0 [nvme_fabrics]
>  nvmf_dev_write+0xae/0x111 [nvme_fabrics]
>  vfs_write+0x144/0x560
>  ksys_write+0xb7/0x140
>  __x64_sys_write+0x42/0x50
>  do_syscall_64+0x35/0x80
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
> 
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Ming Lei <ming.lei@redhat.com>
> Fixes: 20e4d8139319 ("blk-mq: simplify queue mapping & schedule with each possisble CPU")
> Signed-off-by: Bart Van Assche <bvanassche@acm.org>
> ---
>  block/blk-mq.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index 7a5558bbc7f6..1c09c6017ea9 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -579,6 +579,8 @@ struct request *blk_mq_alloc_request_hctx(struct request_queue *q,
>  	if (!blk_mq_hw_queue_mapped(data.hctx))
>  		goto out_queue_exit;
>  	cpu = cpumask_first_and(data.hctx->cpumask, cpu_online_mask);
> +	if (cpu >= nr_cpu_ids)
> +		goto out_queue_exit;
>  	data.ctx = __blk_mq_get_ctx(q, cpu);
>  
>  	if (!q->elevator)
> 

Reviewed-by: Ming Lei <ming.lei@redhat.com>


Thanks,
Ming