Re: [PATCH] scsi: scsi_debug: Fix a warning in resp_write_scat()

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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@xxxxxxxxxx>

Acked-by: Douglas Gilbert <dgilbert@xxxxxxxxxxxx>


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)




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