linux-kernel - Re: iommu: Fix NULL pointer deref when io_page

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Message-ID: <aW5YnTnOJ2dJNuhq@aspen.lan>
Date: Mon, 19 Jan 2026 16:15:25 +0000
From: Daniel Thompson <daniel@...cstar.com>
To: Markus Elfring <Markus.Elfring@....de>
Cc: linux-trace-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Robin Murphy <robin.murphy@....com>, Will Deacon <will@...nel.org>
Subject: Re: iommu: Fix NULL pointer deref when io_page_fault tracepoint fires

On Mon, Jan 19, 2026 at 04:56:04PM +0100, Markus Elfring wrote:
> >> …
> >>> 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

That's not what I asked! You suggested I add people to Cc:, who do you
think I missed?


> >> * 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

I dislike the proposed new summary. I think keeping "io_page_fault"
in the summary is a much better use of characters than spelling
dereference in full.


Daniel.