Re: How to fix problems with the sashiko review model

James Bottomley <[email protected]> writes:

Hi James!

> There doesn't seem to be a Sashiko list, so I added ksummit as the most
> likely one to catch attention.

We actually have one: [email protected] 

> We got this review in SCSI on this
> thread:
>
> https://lore.kernel.org/linux-scsi/[email protected]/
>
> But this part of the review
>
> On Wed, 2026-07-22 at 04:27 +0000, [email protected] wrote:
> [...]
>> > +
>> > +	reply_len = mpi_reply->MsgLength * 4;
>> > +	if (reply_len < event_offset || reply_len > ioc->reply_sz)
>> > +		return false;
>> > +
>> > +	event_data_len = le16_to_cpu(mpi_reply->EventDataLength) *
>> > 4;
>> 
>> [Severity: High]
>> Is there a Time-of-Check to Time-of-Use window here since mpi_reply
>> is read directly from shared DMA memory?
>> 
>> The validation function reads bounds from mpi_reply, but after
>> validation passes, mpt3sas_scsih_event_callback() re-reads fields
>> like EventDataLength and NumEntries directly from the same DMA-backed
>> memory.
>> 
>> Could a malicious device mutate these fields in the window between
>> validation and use to bypass the checks introduced by this patch?
>
> Is wrong.  Hardware may never be presumed to be malicious (well, except
> if it's virtual hardware provided by an untrusted host to a
> confidential guest, but that's a very small list of drivers or it's a
> USB or thunderbolt device designed to attack or exfiltrate data from an
> unattended system).  It may be buggy, but we never presume bugs until
> someone finds a device exhibiting the bug in the field (so we don't
> proactively fix them).
>
> The bigger part of this is that I was looking into how to fix this
> (which might interest a broader swathe of developers than just SCSI). 
> I think the fault is in the review prompts:
>
> https://github.com/masoncl/review-prompts
>
> And what I need to do is to add an additional drivers.md file to
> kernel/subsystems explaining this?  If that's right I can send a pull
> request, but I thought I'd check here because the audience is much
> bigger than if it were to get discussed in the github PR.

I like the idea to inject the security threat model document from the
kernel source tree, I'll add it.

Thanks