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Message-Id: <20121207.141055.2052060513814647508.davem@davemloft.net> Date: Fri, 07 Dec 2012 14:10:55 -0500 (EST) From: David Miller <davem@...emloft.net> To: eric@...it.org Cc: netdev@...r.kernel.org Subject: Re: [RFC PATCH] af_packet: don't to defrag shared skb From: Eric Leblond <eric@...it.org> Date: Fri, 7 Dec 2012 19:56:01 +0100 > This patch is adding a check on skb before trying to defrag the > packet for the hash computation in fanout mode. The goal of this > patch is to avoid an kernel crash in pskb_expand_head. > It appears that under some specific condition there is a shared > skb reaching the defrag code and this lead to a crash due to the > following code: > > if (skb_shared(skb)) > BUG(); > > I've observed this crash under the following condition: > 1. a program is listening to an wifi interface (let say wlan0) > 2. it is using fanout capture in flow load balancing mode > 3. defrag option is on on the fanout socket > 4. the interface disconnect (radio down for example) > 5. the interface reconnect (radio switched up) > 6. once reconnected a single packet is seen with skb->users=2 > 7. the kernel crash in pskb_expand_head at skbuff.c:1035 ... > Signed-off-by: Eric Leblond <eric@...it.org> Thanks Eric. I'll try to figure out if we should instead change the wireless code to avoid sending shared SKBs into the input path like that. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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