[Qemu-devel] [PATCH] SCSI improved LBA-out-of-range checks

[Qemu-devel] [PATCH] SCSI improved LBA-out-of-range checks

[Ronnie Sahlberg]

Paolo, List

Please find a small patch to the scsi emulation.
This patch improves the checkign that the requested lbas are all available.
We check both that lba+len is not going past the end of the device
but also if    lba+len < lba

This second condition could occur for deviously crafted scsi packets where
lba is set to 0xffffffffffffffff  and len is set to 2
in which case lba+len would wrap to 1

[Qemu-devel] [PATCH] SCSI: improve the lba-out-of-range tests for read/write/verify

[Ronnie Sahlberg]

Improve the tests for the LBA to cover more cases, the new test looks like this
        if (r->req.cmd.lba > r->req.cmd.lba + len
        ||  r->req.cmd.lba + len > s->qdev.max_lba) {

For the 16 byte opcodes, the lba is a uint64, so the first check is to make sure that we do not wrap.
For example if an opcode would specify the LBA:0xffffffffffffffff and LEN:2
then lba+len would wrap to 1.

The second part of the test is to verify that ALL requested blocks are available, not just the first one.

Signed-off-by: Ronnie Sahlberg <ronniesahlberg@gmail.com>
---
 hw/scsi-disk.c |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/hw/scsi-disk.c b/hw/scsi-disk.c
index b2f3c0c..40c05de 100644
--- a/hw/scsi-disk.c
+++ b/hw/scsi-disk.c
@@ -1558,7 +1558,8 @@ static int32_t scsi_send_command(SCSIRequest *req, uint8_t *buf)
         if (r->req.cmd.buf[1] & 0xe0) {
             goto fail;
         }
-        if (r->req.cmd.lba > s->qdev.max_lba) {
+        if (r->req.cmd.lba > r->req.cmd.lba + len
+        ||  r->req.cmd.lba + len > s->qdev.max_lba) {
             goto illegal_lba;
         }
         r->sector = r->req.cmd.lba * (s->qdev.blocksize / 512);
@@ -1581,7 +1582,8 @@ static int32_t scsi_send_command(SCSIRequest *req, uint8_t *buf)
         if (r->req.cmd.buf[1] & 0xe0) {
             goto fail;
         }
-        if (r->req.cmd.lba > s->qdev.max_lba) {
+        if (r->req.cmd.lba > r->req.cmd.lba + len
+        ||  r->req.cmd.lba + len > s->qdev.max_lba) {
             goto illegal_lba;
         }
         r->sector = r->req.cmd.lba * (s->qdev.blocksize / 512);
-- 
1.7.3.1

Re: [Qemu-devel] [PATCH] SCSI: improve the lba-out-of-range tests for read/write/verify

[Paolo Bonzini]

Il 12/07/2012 08:52, Ronnie Sahlberg ha scritto:
> Improve the tests for the LBA to cover more cases, the new test looks like this
>         if (r->req.cmd.lba > r->req.cmd.lba + len
>         ||  r->req.cmd.lba + len > s->qdev.max_lba) {
> 
> For the 16 byte opcodes, the lba is a uint64, so the first check is to make sure that we do not wrap.
> For example if an opcode would specify the LBA:0xffffffffffffffff and LEN:2
> then lba+len would wrap to 1.
> 
> The second part of the test is to verify that ALL requested blocks are available, not just the first one.

Fixed code style for || and applied to scsi-next.

Thanks!

Paolo

> Signed-off-by: Ronnie Sahlberg <ronniesahlberg@gmail.com>
> ---
>  hw/scsi-disk.c |    6 ++++--
>  1 files changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/scsi-disk.c b/hw/scsi-disk.c
> index b2f3c0c..40c05de 100644
> --- a/hw/scsi-disk.c
> +++ b/hw/scsi-disk.c
> @@ -1558,7 +1558,8 @@ static int32_t scsi_send_command(SCSIRequest *req, uint8_t *buf)
>          if (r->req.cmd.buf[1] & 0xe0) {
>              goto fail;
>          }
> -        if (r->req.cmd.lba > s->qdev.max_lba) {
> +        if (r->req.cmd.lba > r->req.cmd.lba + len
> +        ||  r->req.cmd.lba + len > s->qdev.max_lba) {
>              goto illegal_lba;
>          }
>          r->sector = r->req.cmd.lba * (s->qdev.blocksize / 512);
> @@ -1581,7 +1582,8 @@ static int32_t scsi_send_command(SCSIRequest *req, uint8_t *buf)
>          if (r->req.cmd.buf[1] & 0xe0) {
>              goto fail;
>          }
> -        if (r->req.cmd.lba > s->qdev.max_lba) {
> +        if (r->req.cmd.lba > r->req.cmd.lba + len
> +        ||  r->req.cmd.lba + len > s->qdev.max_lba) {
>              goto illegal_lba;
>          }
>          r->sector = r->req.cmd.lba * (s->qdev.blocksize / 512);
> 

Re: [Qemu-devel] [PATCH] SCSI: improve the lba-out-of-range tests for read/write/verify

[ronnie sahlberg]

Sorry,   there is a bug in it.

Can you change it to :
      ||  r->req.cmd.lba + len > s->qdev.max_lba + 1) {

or else the last lba of the device will be flagged as out of range.



On Thu, Jul 12, 2012 at 5:04 PM, Paolo Bonzini <pbonzini@redhat.com> wrote:
> Il 12/07/2012 08:52, Ronnie Sahlberg ha scritto:
>> Improve the tests for the LBA to cover more cases, the new test looks like this
>>         if (r->req.cmd.lba > r->req.cmd.lba + len
>>         ||  r->req.cmd.lba + len > s->qdev.max_lba) {
>>
>> For the 16 byte opcodes, the lba is a uint64, so the first check is to make sure that we do not wrap.
>> For example if an opcode would specify the LBA:0xffffffffffffffff and LEN:2
>> then lba+len would wrap to 1.
>>
>> The second part of the test is to verify that ALL requested blocks are available, not just the first one.
>
> Fixed code style for || and applied to scsi-next.
>
> Thanks!
>
> Paolo
>
>> Signed-off-by: Ronnie Sahlberg <ronniesahlberg@gmail.com>
>> ---
>>  hw/scsi-disk.c |    6 ++++--
>>  1 files changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/hw/scsi-disk.c b/hw/scsi-disk.c
>> index b2f3c0c..40c05de 100644
>> --- a/hw/scsi-disk.c
>> +++ b/hw/scsi-disk.c
>> @@ -1558,7 +1558,8 @@ static int32_t scsi_send_command(SCSIRequest *req, uint8_t *buf)
>>          if (r->req.cmd.buf[1] & 0xe0) {
>>              goto fail;
>>          }
>> -        if (r->req.cmd.lba > s->qdev.max_lba) {
>> +        if (r->req.cmd.lba > r->req.cmd.lba + len
>> +        ||  r->req.cmd.lba + len > s->qdev.max_lba) {
>>              goto illegal_lba;
>>          }
>>          r->sector = r->req.cmd.lba * (s->qdev.blocksize / 512);
>> @@ -1581,7 +1582,8 @@ static int32_t scsi_send_command(SCSIRequest *req, uint8_t *buf)
>>          if (r->req.cmd.buf[1] & 0xe0) {
>>              goto fail;
>>          }
>> -        if (r->req.cmd.lba > s->qdev.max_lba) {
>> +        if (r->req.cmd.lba > r->req.cmd.lba + len
>> +        ||  r->req.cmd.lba + len > s->qdev.max_lba) {
>>              goto illegal_lba;
>>          }
>>          r->sector = r->req.cmd.lba * (s->qdev.blocksize / 512);
>>
>
>

Re: [Qemu-devel] [PATCH] SCSI: improve the lba-out-of-range tests for read/write/verify

[Paolo Bonzini]

Il 12/07/2012 09:06, ronnie sahlberg ha scritto:
> Sorry,   there is a bug in it.
> 
> Can you change it to :
>       ||  r->req.cmd.lba + len > s->qdev.max_lba + 1) {
> 
> or else the last lba of the device will be flagged as out of range.

Yes, done that already.  Can you add a test for the last LBA to your
testsuite?

Paolo