Re: [Qemu-devel] [PATCH] scsi-disk: fix buffer overflow

From: Aurelien Jarno <aurelien@aurel32.net>
To: Gerd Hoffmann <kraxel@redhat.com>
Cc: qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [PATCH] scsi-disk: fix buffer overflow
Date: Sat, 13 Mar 2010 12:19:51 +0100	[thread overview]
Message-ID: <20100313111951.GB26705@volta.aurel32.net> (raw)
In-Reply-To: <1268239637-24524-1-git-send-email-kraxel@redhat.com>

On Wed, Mar 10, 2010 at 05:47:17PM +0100, Gerd Hoffmann wrote:
> In case s->version is shorter than 4 bytes we overflow the memcpy src
> buffer.  Fix it by clearing the target buffer, then copy only the
> amount of bytes we actually have.
> 
> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
> ---
>  hw/scsi-disk.c |    4 +++-
>  1 files changed, 3 insertions(+), 1 deletions(-)
> 
> diff --git a/hw/scsi-disk.c b/hw/scsi-disk.c
> index b2f61fe..5792545 100644
> --- a/hw/scsi-disk.c
> +++ b/hw/scsi-disk.c
> @@ -459,7 +459,9 @@ static int scsi_disk_emulate_inquiry(SCSIRequest *req, uint8_t *outbuf)
>          memcpy(&outbuf[16], "QEMU HARDDISK   ", 16);
>      }
>      memcpy(&outbuf[8], "QEMU    ", 8);
> -    memcpy(&outbuf[32], s->version ? s->version : QEMU_VERSION, 4);
> +    memset(&outbuf[32], 0, 4);
> +    memcpy(&outbuf[32], s->version ? s->version : QEMU_VERSION,
> +           MIN(4, strlen(s->version ? s->version : QEMU_VERSION)));

Wouldn't be simpler to use strncpy() instead of a memcpy()?

>      /* Identify device as SCSI-3 rev 1.
>         Some later commands are also implemented. */
>      outbuf[2] = 5;
> -- 
> 1.6.6.1
> 
> 
> 
> 

-- 
Aurelien Jarno                          GPG: 1024D/F1BCDB73
aurelien@aurel32.net                 http://www.aurel32.net