Re: [PATCH] irqdomain: check irq mapping against domain size

[Ben Dooks]

On 05/11/2021 12:09, Marc Zyngier wrote:
> Hi Ben,
>
> On Fri, 05 Nov 2021 09:06:01 +0000,
> Ben Dooks <ben.dooks@xxxxxxxxxxxxxxx> wrote:
> > The irq translate code does not check the irq number against
> > the maximum a domain can handle. This can cause an OOPS if
> > the firmware data has been damaged in any way. Check the intspec
> > or fwdata against the irqdomain and return -EINVAL if over.
> >
> > This is the result of bug somewhere in the boot of a SiFive Unmatched
> > board where the 5th argument of the pcie node is being damaged which
> > causes an OOPS in the startup code.
> >
> > Signed-off-by: Ben Dooks <ben.dooks@xxxxxxxxxxxxxxx>
> > ---
> >   kernel/irq/irqdomain.c | 8 ++++++++
> >   1 file changed, 8 insertions(+)
> >
> > diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c
> > index 6284443b87ec..e61397420723 100644
> > --- a/kernel/irq/irqdomain.c
> > +++ b/kernel/irq/irqdomain.c
> > @@ -906,6 +906,8 @@ int irq_domain_xlate_onecell(struct irq_domain *d, struct device_node *ctrlr,
> >   {
> >   	if (WARN_ON(intsize < 1))
> >   		return -EINVAL;
> > +	if (WARN_ON(intspec[0] > d->hwirq_max))
> > +		return -EINVAL;
>
> This doesn't seem right.
>
> For a start, d->hwirq_max is 0 when the domain is backed by a radix
> tree. Also, nothing says that what you read from the DT is something
> that should be directly meaningful to the irqdomain. A driver could
> well call into this and perform some extra processing on the data
> before it lands into the irqdomain.

Thanks, didn't know that.

would doing:

+	if (WARN_ON(d->hwirq_max && intspec[0] > d->hwirq_max))
+		return -EINVAL;

be acceptable?

> In general, this looks like DT validation code, and I'm not keen on
> that in the core code.

I thought the core was probably the only place to do this, I didn't
think the DT code would know about the hardware capabilities of the
DT controller.

It seems bad that some corrupted data can just crash the kernel in
a non-recoverable and early way that requires some specific debug
features like early-printk enabled. Would anyone else have a way of
fixing this?

--
Ben Dooks				http://www.codethink.co.uk/
Senior Engineer				Codethink - Providing Genius

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