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

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Date:   Fri, 11 Nov 2022 02:05:25 -0800
From:   Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>
To:     unlisted-recipients:; (no To-header on input)
Cc:     harshit.m.mogalapalli@...cle.com, error27@...il.com,
        harshit.m.mogalapalli@...il.com,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Douglas Gilbert <dgilbert@...erlog.com>,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] scsi: scsi_debug: Fix a warning in resp_write_scat()

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>
---
 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)
-- 
2.38.1