Re: Please consider mainline commit 9393c8de628c for stable

Re: Please consider mainline commit 9393c8de628c for stable

[Sasha Levin]

On Tue, Nov 12, 2019 at 03:52:47PM +1300, Michael Schmitz wrote:
>Dear stable kernel maintainers,
>
>please consider including commit 9393c8de628c ("scsi: core: Handle 
>drivers which set sg_tablesize to zero") for inclusion in stable.
>
>The commit fixes a long standing bug that affects all SCSI low-level 
>drivers setting sg_tablesize to zero, introduced in commit d285203c 
>("scsi: add support for a blk-mq based I/O path.") around kernel 
>version 3.16.
>
>Use of the option use_blk_mq=y in kernel versions prior to 5.1, and 
>any use of such drivers in later kernels, will result in a null 
>pointer dereference from the block layer.
>
>I hadn't expected Martin Petersen to pick my fix over another one 
>submitted by Finn Thain, so I never added CC: or Fixes: tags.

Could you provide a backport for 4.19 and older?

We would need to work around not having 3dccdf53c2f3 ("scsi: core: avoid
preallocating big SGL for data") in older kernels, and I'm not confident
about what I ended up as a backport without ability to test it.

-- 
Thanks,
Sasha

Re: Please consider mainline commit 9393c8de628c for stable

[Michael Schmitz]

Hi Sasha,

Am 13.11.2019 um 14:27 schrieb Sasha Levin:
> On Tue, Nov 12, 2019 at 03:52:47PM +1300, Michael Schmitz wrote:
>> Dear stable kernel maintainers,
>>
>> please consider including commit 9393c8de628c ("scsi: core: Handle
>> drivers which set sg_tablesize to zero") for inclusion in stable.
>>
>> The commit fixes a long standing bug that affects all SCSI low-level
>> drivers setting sg_tablesize to zero, introduced in commit d285203c
>> ("scsi: add support for a blk-mq based I/O path.") around kernel
>> version 3.16.
>>
>> Use of the option use_blk_mq=y in kernel versions prior to 5.1, and
>> any use of such drivers in later kernels, will result in a null
>> pointer dereference from the block layer.
>>
>> I hadn't expected Martin Petersen to pick my fix over another one
>> submitted by Finn Thain, so I never added CC: or Fixes: tags.
>
> Could you provide a backport for 4.19 and older?
>
> We would need to work around not having 3dccdf53c2f3 ("scsi: core: avoid
> preallocating big SGL for data") in older kernels, and I'm not confident
> about what I ended up as a backport without ability to test it.

I hadn't spotted that. From  what I've seen, that commit renamed 
scsi_mq_inline_sgl_size() by scsi_mq_sgl_size() (among all the other 
changes) so modifying my patch with that in mind should suffice.

For safety, I'll test that version though.

Cheers,

	Michael