From: Michael Ellerman <mpe@ellerman•id.au>
To: "Thomas Weißschuh" <thomas.weissschuh@linutronix•de>,
"Rob Herring" <robh@kernel•org>,
"Saravana Kannan" <saravanak@google•com>
Cc: devicetree@vger•kernel.org, linux-kernel@vger•kernel.org,
"Thomas Weißschuh" <thomas.weissschuh@linutronix•de>,
linuxppc-dev@lists•ozlabs.org
Subject: Re: [PATCH] of: address: Unify resource bounds overflow checking
Date: Fri, 13 Sep 2024 23:15:21 +1000 [thread overview]
Message-ID: <87plp7r8ye.fsf@mail.lhotse> (raw)
In-Reply-To: <20240906-of-address-overflow-v1-1-19567aaa61da@linutronix.de>
Thomas Weißschuh <thomas.weissschuh@linutronix•de> writes:
> The members "start" and "end" of struct resource are of type
> "resource_size_t" which can be 32bit wide.
> Values read from OF however are always 64bit wide.
>
> Refactor the diff overflow checks into a helper function.
> Also extend the checks to validate each calculation step.
>
> Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix•de>
> ---
> drivers/of/address.c | 45 ++++++++++++++++++++++++++-------------------
> 1 file changed, 26 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/of/address.c b/drivers/of/address.c
> index 7e59283a4472..df854bb427ce 100644
> --- a/drivers/of/address.c
> +++ b/drivers/of/address.c
> @@ -198,6 +198,25 @@ static u64 of_bus_pci_map(__be32 *addr, const __be32 *range, int na, int ns,
>
> #endif /* CONFIG_PCI */
>
> +static int __of_address_resource_bounds(struct resource *r, u64 start, u64 size)
> +{
> + u64 end = start;
> +
> + if (overflows_type(start, r->start))
> + return -EOVERFLOW;
> + if (size == 0)
> + return -EOVERFLOW;
> + if (check_add_overflow(end, size - 1, &end))
> + return -EOVERFLOW;
> + if (overflows_type(end, r->end))
> + return -EOVERFLOW;
This breaks PCI on powerpc qemu. Part of the PCI probe reads a resource
that's zero sized, which used to succeed but now fails due to the size
check above.
The diff below fixes it for me.
It leaves r.end == r.start, which is fine in my case, because the code
only uses r.start.
And it seems more sane than the old code which would return
end = start - 1, for zero sized resources.
cheers
diff --git a/drivers/of/address.c b/drivers/of/address.c
index df854bb427ce..a001e789a6c4 100644
--- a/drivers/of/address.c
+++ b/drivers/of/address.c
@@ -204,9 +204,7 @@ static int __of_address_resource_bounds(struct resource *r, u64 start, u64 size)
if (overflows_type(start, r->start))
return -EOVERFLOW;
- if (size == 0)
- return -EOVERFLOW;
- if (check_add_overflow(end, size - 1, &end))
+ if (size > 0 && check_add_overflow(end, size - 1, &end))
return -EOVERFLOW;
if (overflows_type(end, r->end))
return -EOVERFLOW;
next parent reply other threads:[~2024-09-13 13:15 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20240906-of-address-overflow-v1-1-19567aaa61da@linutronix.de>
2024-09-13 13:15 ` Michael Ellerman [this message]
2024-09-13 18:56 ` [PATCH] of: address: Unify resource bounds overflow checking Rob Herring
2024-09-13 23:10 ` Michael Ellerman
2025-01-08 14:04 ` Basharath Hussain Khaja
2025-01-08 22:43 ` Rob Herring
2025-01-17 6:53 ` Basharath Hussain Khaja
2025-01-17 13:06 ` Thomas Weißschuh
2025-01-20 10:09 ` Basharath Hussain Khaja
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