Messages in this thread | | | Date | Thu, 21 Mar 2024 14:39:33 +0300 | Subject | Re: [PATCH] flow_dissector: prevent NULL pointer dereference in __skb_flow_dissect | From | Denis Kirjanov <> |
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On 3/21/24 13:57, Jiri Pirko wrote: > Thu, Mar 21, 2024 at 10:36:53AM CET, abelova@astralinux.ru wrote: >> >> >> 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 > > Okay. So would it be possible to 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@davemloft.net> >>> Date: Sat Aug 23 12:13:41 2014 -0700 >>> >>> net: Allow raw buffers to be passed into the flow dissector. >>> >> >> Got it.
Looks like it's a static checker, there is no actual bug report or kernel oops/crash
>> >>> >>>> 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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