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Message-ID: <Zfrmv4u0tVcYGS5n@nanopsycho>
Date: Wed, 20 Mar 2024 14:38:07 +0100
From: Jiri Pirko <jiri@...nulli.us>
To: Anastasia Belova <abelova@...ralinux.ru>
Cc: "David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
linux-kernel@...r.kernel.org, lvc-project@...uxtesting.org
Subject: Re: [PATCH] flow_dissector: prevent NULL pointer dereference in
__skb_flow_dissect
Wed, Mar 20, 2024 at 01:56:35PM CET, abelova@...ralinux.ru wrote:
>skb is an optional parameter, so it may be NULL.
>Add check defore dereference in eth_hdr.
>
>Found by Linux Verification Center (linuxtesting.org) with SVACE.
Either drop this line which provides no value, or attach a link to the
actual report.
>
>Fixes: 67a900cc0436 ("flow_dissector: introduce support for Ethernet addresses")
This looks incorrect. I believe that this is the offending commit:
commit 690e36e726d00d2528bc569809048adf61550d80
Author: David S. Miller <davem@...emloft.net>
Date: Sat Aug 23 12:13:41 2014 -0700
net: Allow raw buffers to be passed into the flow dissector.
>Signed-off-by: Anastasia Belova <abelova@...ralinux.ru>
>---
> net/core/flow_dissector.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
>diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
>index 272f09251343..05db3a8aa771 100644
>--- a/net/core/flow_dissector.c
>+++ b/net/core/flow_dissector.c
>@@ -1137,7 +1137,7 @@ bool __skb_flow_dissect(const struct net *net,
> rcu_read_unlock();
> }
>
>- if (dissector_uses_key(flow_dissector,
>+ if (skb && dissector_uses_key(flow_dissector,
> FLOW_DISSECTOR_KEY_ETH_ADDRS)) {
> struct ethhdr *eth = eth_hdr(skb);
> struct flow_dissector_key_eth_addrs *key_eth_addrs;
Looks like FLOW_DISSECT_RET_OUT_BAD should be returned in case the
FLOW_DISSECTOR_KEY_ETH_ADDRS are selected and there is no skb, no?
pw-bot: cr
>--
>2.30.2
>
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