linux-kernel - RE: [EXTERNAL] [PATCH 1/1] scsi: Fix possible buffer overflows in storvsc

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Date:   Tue, 8 Dec 2020 16:30:01 +0000
From:   KY Srinivasan <kys@...rosoft.com>
To:     Xiaohui Zhang <ruc_zhangxiaohui@....com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Wei Liu <wei.liu@...nel.org>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [EXTERNAL] [PATCH 1/1] scsi: Fix possible buffer overflows in
 storvsc_queuecommand



> -----Original Message-----
> From: Xiaohui Zhang <ruc_zhangxiaohui@....com>
> Sent: Tuesday, December 8, 2020 5:19 AM
> To: Xiaohui Zhang <ruc_zhangxiaohui@....com>; KY Srinivasan
> <kys@...rosoft.com>; Haiyang Zhang <haiyangz@...rosoft.com>; Stephen
> Hemminger <sthemmin@...rosoft.com>; Wei Liu <wei.liu@...nel.org>;
> James E.J. Bottomley <jejb@...ux.ibm.com>; Martin K. Petersen
> <martin.petersen@...cle.com>; linux-hyperv@...r.kernel.org; linux-
> scsi@...r.kernel.org; linux-kernel@...r.kernel.org
> Subject: [EXTERNAL] [PATCH 1/1] scsi: Fix possible buffer overflows in
> storvsc_queuecommand
> 
> From: Zhang Xiaohui <ruc_zhangxiaohui@....com>
> 
> storvsc_queuecommand() calls memcpy() without checking the destination size
> may trigger a buffer overflower, which a local user could use to cause denial of
> service or the execution of arbitrary code.
> Fix it by putting the length check before calling memcpy().
> 
> Signed-off-by: Zhang Xiaohui <ruc_zhangxiaohui@....com>
> ---
>  drivers/scsi/storvsc_drv.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c index
> 0c65fbd41..09b60a4c0 100644
> --- a/drivers/scsi/storvsc_drv.c
> +++ b/drivers/scsi/storvsc_drv.c
> @@ -1729,6 +1729,8 @@ static int storvsc_queuecommand(struct Scsi_Host
> *host, struct scsi_cmnd *scmnd)
> 
>  	vm_srb->cdb_length = scmnd->cmd_len;
> 
> +	if (vm_srb->cdb_length > STORVSC_MAX_CMD_LEN)
> +		vm_srb->cdb_length = STORVSC_MAX_CMD_LEN;
>  	memcpy(vm_srb->cdb, scmnd->cmnd, vm_srb->cdb_length);

The data  structure is sized correctly to handle the max command length. Besides
your check is bogus - you cannot truncate the command!

K. Y
> 
>  	sgl = (struct scatterlist *)scsi_sglist(scmnd);
> --
> 2.17.1