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

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Message-ID: <fa578a51-5bae-21be-df5b-a72f5f79c662@oracle.com>
Date:   Sat, 12 Nov 2022 12:43:40 +0530
From:   Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>
To:     dgilbert@...erlog.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()

Hi Doug,

On 11/11/22 10:53 pm, Douglas Gilbert wrote:
> 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>
> 

Thank you very much for checking the patch.

We have two more similar cases in the scsi_debug.c file in resp_verify() 
and resp_report_zones() functions. These are also detected using static 
analysis with smatch.

I have sent out patches for those.

Thanks,
Harshit

> 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)
>