linux-kernel - Re: [PATCH] scsi: scsi_debug: Fix a warning in resp_write

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Date:   Fri, 11 Nov 2022 12:23:51 -0500
From:   Douglas Gilbert <dgilbert@...erlog.com>
To:     Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>
Cc:     error27@...il.com, harshit.m.mogalapalli@...il.com,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] scsi: scsi_debug: Fix a warning in resp_write_scat()

On 2022-11-11 05:05, Harshit Mogalapalli wrote:
> As 'lbdof_blen' is coming from user, if the size in kzalloc()
> is >= MAX_ORDER then we hit a warning.
> 
> Call trace:
> 
> sg_ioctl
>   sg_ioctl_common
>     scsi_ioctl
>      sg_scsi_ioctl
>       blk_execute_rq
>        blk_mq_sched_insert_request
>         blk_mq_run_hw_queue
>          __blk_mq_delay_run_hw_queue
>           __blk_mq_run_hw_queue
>            blk_mq_sched_dispatch_requests
>             __blk_mq_sched_dispatch_requests
>              blk_mq_dispatch_rq_list
>               scsi_queue_rq
>                scsi_dispatch_cmd
>                 scsi_debug_queuecommand
>                  schedule_resp
>                   resp_write_scat
> 
> If you try to allocate a memory larger than(>=) MAX_ORDER, then kmalloc()
> will definitely fail.  It creates a stack trace and messes up dmesg.
> The user controls the size here so if they specify a too large size it
> will fail.
> 
> Add __GFP_NOWARN in order to avoid too large allocation warning.
> This is detected by static analysis using smatch.
> 
> Fixes: 481b5e5c7949 ("scsi: scsi_debug: add resp_write_scat function")
> Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>

Acked-by: Douglas Gilbert <dgilbert@...erlog.com>

Thanks.

> ---
>   drivers/scsi/scsi_debug.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
> index 697fc57bc711..273224d29ce9 100644
> --- a/drivers/scsi/scsi_debug.c
> +++ b/drivers/scsi/scsi_debug.c
> @@ -3778,7 +3778,7 @@ static int resp_write_scat(struct scsi_cmnd *scp,
>   		mk_sense_buffer(scp, ILLEGAL_REQUEST, INVALID_FIELD_IN_CDB, 0);
>   		return illegal_condition_result;
>   	}
> -	lrdp = kzalloc(lbdof_blen, GFP_ATOMIC);
> +	lrdp = kzalloc(lbdof_blen, GFP_ATOMIC | __GFP_NOWARN);
>   	if (lrdp == NULL)
>   		return SCSI_MLQUEUE_HOST_BUSY;
>   	if (sdebug_verbose)