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SubjectRe: [PATCH] scsi: sr: fix oob access in get_capabilities
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On 2017/3/20 22:29, Martin K. Petersen wrote:
> Kefeng Wang <wangkefeng.wang@huawei.com> writes:
>
> Kefeng,
>
>> The issue still exists, the patch return zero in scsi_mode_sense(), but zero means
>> SAM_STAT_GOOD in scsi_status_is_good(), so n will be still bigger than 512;
>
> OK, I checked the other users of scsi_mode_sense(). So let's keep this
> fix local to sr.c for now.
>
> How about the following?
>
>
> scsi: sr: Sanity check returned mode data
>
> Kefeng Wang discovered that old versions of the QEMU CD driver would
> return mangled mode data causing us to walk off the end of the buffer in
> an attempt to parse it. Sanity check the returned mode sense data.
>
> Cc: <stable@vger.kernel.org>
> Reported-by: Kefeng Wang <wangkefeng.wang@huawei.com>
> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
>
> diff --git a/drivers/scsi/sr.c b/drivers/scsi/sr.c
> index 0b29b9329b1c..a8f630213a1a 100644
> --- a/drivers/scsi/sr.c
> +++ b/drivers/scsi/sr.c
> @@ -836,6 +836,7 @@ static void get_capabilities(struct scsi_cd *cd)
> unsigned char *buffer;
> struct scsi_mode_data data;
> struct scsi_sense_hdr sshdr;
> + unsigned int ms_len = 128;
> int rc, n;
>
> static const char *loadmech[] =
> @@ -862,10 +863,11 @@ static void get_capabilities(struct scsi_cd *cd)
> scsi_test_unit_ready(cd->device, SR_TIMEOUT, MAX_RETRIES, &sshdr);
>
> /* ask for mode page 0x2a */
> - rc = scsi_mode_sense(cd->device, 0, 0x2a, buffer, 128,
> + rc = scsi_mode_sense(cd->device, 0, 0x2a, buffer, ms_len,
> SR_TIMEOUT, 3, &data, NULL);
>

move n = data.header_length + data.block_descriptor_length; here,

> - if (!scsi_status_is_good(rc)) {
> + if (!scsi_status_is_good(rc) || data.length > ms_len ||
> + data.header_length + data.block_descriptor_length > data.length) {

n > data.length

Tested-by: Kefeng Wang <wangkefeng.wang@huawei.com>

Thanks,
Kefeng

> /* failed, drive doesn't have capabilities mode page */
> cd->cdi.speed = 1;
> cd->cdi.mask |= (CDC_CD_R | CDC_CD_RW | CDC_DVD_R |
>
>
>
> .
>

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