Subject: Re: [PATCH] sd: fix uninitialized variable access in error handling
To: Arnd Bergmann <arnd@arndb.de>,
        "James E.J. Bottomley" <jejb@linux.vnet.ibm.com>,
        "Martin K. Petersen" <martin.petersen@oracle.com>
References: <20161021153246.3456962-1-arnd@arndb.de>
CC: Hannes Reinecke <hare@suse.de>,
        Shaun Tancheff <shaun.tancheff@seagate.com>, Jens Axboe <axboe@fb.com>,
        Damien Le Moal <damien.lemoal@hgst.com>, <linux-scsi@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>
From: Damien Le Moal <damien.lemoal@wdc.com>
Organization: Western Digital
Message-ID: <4bd72b9c-7826-0bfd-7004-09732c774091@wdc.com>
Date: Mon, 24 Oct 2016 08:37:37 +0900
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On 10/22/16 00:32, Arnd Bergmann wrote:
> If sd_zbc_report_zones fails, the check for 'zone_blocks == 0'
> later in the function accesses uninitialized data:
> 
> drivers/scsi/sd_zbc.c: In function ‘sd_zbc_read_zones’:
> drivers/scsi/sd_zbc.c:520:7: error: ‘zone_blocks’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
> 
> This sets it to zero, which has the desired effect of leaving
> the sd_zbc_read_zones successfully with sdkp->zone_blocks = 0.
> 
> Fixes: 89d947561077 ("sd: Implement support for ZBC devices")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
>  drivers/scsi/sd_zbc.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/scsi/sd_zbc.c b/drivers/scsi/sd_zbc.c
> index 16d3fa62d8ac..d5b3bd915d9e 100644
> --- a/drivers/scsi/sd_zbc.c
> +++ b/drivers/scsi/sd_zbc.c
> @@ -455,8 +455,10 @@ static int sd_zbc_check_zone_size(struct scsi_disk *sdkp)
>  
>  	/* Do a report zone to get the same field */
>  	ret = sd_zbc_report_zones(sdkp, buf, SD_ZBC_BUF_SIZE, 0);
> -	if (ret)
> +	if (ret) {
> +		zone_blocks = 0;
>  		goto out;
> +	}
>  
>  	same = buf[4] & 0x0f;
>  	if (same > 0) {

Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>

-- 
Damien Le Moal, Ph.D.
Sr. Manager, System Software Research Group,
Western Digital Corporation
Damien.LeMoal@wdc.com
(+81) 0466-98-3593 (ext. 513593)
1 kirihara-cho, Fujisawa,
Kanagawa, 252-0888 Japan
www.wdc.com, www.hgst.com