Re: [Qemu-devel] [PATCH] scsi: fix buffer overflow in scsi_req_parse_cdb (CVE-2015-5158)

["Daniel P. Berrange" <berrange@redhat.com>]

On Wed, Jul 22, 2015 at 04:18:00PM +0200, Paolo Bonzini wrote:
> This is a guest-triggerable buffer overflow present in QEMU 2.2.0
> and newer.  scsi_cdb_length returns -1 as an error value, but the
> caller does not check it.
> 
> Luckily, the massive overflow means that QEMU will just SIGSEGV,
> making the impact much smaller.

FWIW, would be nice to mention which disk frontends could trigger
this bug. eg was it all of the devices in hw/scsi/ or just a subset ?

> 
> Reported-by: Zhu Donghai (朱东海) <donghai.zdh@alibaba-inc.com>
> Fixes: 1894df02811f6b79ea3ffbf1084599d96f316173
> Cc: qemu-stable@nongnu.org
> ---
>  hw/scsi/scsi-bus.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/scsi/scsi-bus.c b/hw/scsi/scsi-bus.c
> index f50b2f0..f0ae462 100644
> --- a/hw/scsi/scsi-bus.c
> +++ b/hw/scsi/scsi-bus.c
> @@ -1239,10 +1239,15 @@ int scsi_cdb_length(uint8_t *buf) {
>  int scsi_req_parse_cdb(SCSIDevice *dev, SCSICommand *cmd, uint8_t *buf)
>  {
>      int rc;
> +    int len;
>  
>      cmd->lba = -1;
> -    cmd->len = scsi_cdb_length(buf);
> +    len = scsi_cdb_length(buf);
> +    if (len < 0) {
> +        return -1;
> +    }
>  
> +    cmd->len = len;
>      switch (dev->type) {
>      case TYPE_TAPE:
>          rc = scsi_req_stream_xfer(cmd, dev, buf);


Regards,
Daniel
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