netfilter: nf_iterate: fix incorrect RCU usage
As noticed by Eric, nf_iterate doesn't use RCU correctly by accessing the prev pointer of a RCU protected list element when a verdict of NF_REPEAT is issued. Fix by jumping backwards to the hook invocation directly instead of loading the previous list element before continuing the list iteration. Reported-by: Eric Dumazet <eric.dumazet@gmail.com> Acked-by: Eric Dumazet <eric.dumazet@gmail.com> Signed-off-by: Patrick McHardy <kaber@trash.net>
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@ -133,6 +133,7 @@ unsigned int nf_iterate(struct list_head *head,
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/* Optimization: we don't need to hold module
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reference here, since function can't sleep. --RR */
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repeat:
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verdict = elem->hook(hook, skb, indev, outdev, okfn);
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if (verdict != NF_ACCEPT) {
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#ifdef CONFIG_NETFILTER_DEBUG
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@ -145,7 +146,7 @@ unsigned int nf_iterate(struct list_head *head,
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#endif
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if (verdict != NF_REPEAT)
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return verdict;
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*i = (*i)->prev;
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goto repeat;
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}
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}
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return NF_ACCEPT;
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