iommu: Fix NULL pointer deref when io_page_fault tracepoint fires

[Markus Elfring]

>> …
>>> Fix this by adding logic to the tracepoint to safely propagate NULL.
>>
>> * How do you think about to add any tags (like “Fixes” and “Cc”) accordingly?
> 
> I could add a
> 
> Fixes: f8f934c180f6 ("iommu/arm-smmu: Add support for driver IOMMU fault handlers")
> 
> However, who do you think I neglected to Cc:?

See also once more:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/submitting-patches.rst?h=v6.19-rc5#n262
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/stable-kernel-rules.rst?h=v6.19-rc5#n34


>> * Would a summary phrase like “Prevent null pointer dereference for a tracepoint”
>>   be a bit nicer?
> 
> I don't understand what is wrong with the original phrasing. Can you
> explain why this change matters to you?

* Questionable abbreviation “deref”

* when clause


Regards,
Markus