linux-kernel - Re: [PATCH] scsi: sd: don't crash the host on invalid commands

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Date:   Thu, 20 Sep 2018 11:18:19 -0700
From:   Bart Van Assche <bvanassche@....org>
To:     Johannes Thumshirn <jthumshirn@...e.de>,
        "Martin K . Petersen" <martin.petersen@...cle.com>
Cc:     Linux Kernel Mailinglist <linux-kernel@...r.kernel.org>,
        Linux SCSI Mailinglist <linux-scsi@...r.kernel.org>,
        Hannes Reinecke <hare@...e.de>, Christoph Hellwig <hch@....de>
Subject: Re: [PATCH] scsi: sd: don't crash the host on invalid commands

On Thu, 2018-09-20 at 09:19 +0200, Johannes Thumshirn wrote:
> When sd_init_command() get's a with a unknown req_op() it crashes the
> system via BUG().
> 
> This makes debugging the actual reason for the broken request
> cmd_flags pretty hard as the system is down before it's able to write
> out debugging data on the serial console or the trace buffer.
> 
> Change the BUG() to a WARN_ON() and return BLKPREP_KILL to fail
> gracefully and return an I/O error to the producer of the request.
> 
> Signed-off-by: Johannes Thumshirn <jthumshirn@...e.de>
> Cc: Hannes Reinecke <hare@...e.de>
> Cc: Bart Van Assche <bvanassche@....org>
> Cc: Christoph Hellwig <hch@....de>
> ---
> Fixed Typo in Bart's mail, sorry for this.
> 
>  drivers/scsi/sd.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
> index b79b366a94f7..19f28962d65b 100644
> --- a/drivers/scsi/sd.c
> +++ b/drivers/scsi/sd.c
> @@ -1276,7 +1276,8 @@ static int sd_init_command(struct scsi_cmnd *cmd)
>  	case REQ_OP_ZONE_RESET:
>  		return sd_zbc_setup_reset_cmnd(cmd);
>  	default:
> -		BUG();
> +		WARN_ON(1);
> +		return BLKPREP_KILL;
>  	}
>  }

Have you considered to use WARN_ON_ONCE() instead of WARN_ON(1)? Otherwise
this patch looks good to me.

Thanks,

Bart.