Messages in this thread | | | Date | Thu, 21 Mar 2024 12:36:53 +0300 | Subject | Re: [PATCH] flow_dissector: prevent NULL pointer dereference in __skb_flow_dissect | From | Anastasia Belova <> |
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20/03/24 16:38, Jiri Pirko пишет: > Wed, Mar 20, 2024 at 01:56:35PM CET, abelova@astralinux.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. >
It is an established practice for our project. You can find 700+ applied patches with similar line: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/log/?qt=grep&q=linuxtesting.org
>> 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@davemloft.net> > Date: Sat Aug 23 12:13:41 2014 -0700 > > net: Allow raw buffers to be passed into the flow dissector. >
Got it.
> >> Signed-off-by: Anastasia Belova <abelova@astralinux.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?
I agree, I'll send the second version.
Anastasia Belova
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