mbuf: do not restore dying interfaces
When we remove an interface it is first removed from the interface list V_ifnet (by if_unlink_ifnet()) and marked as IFF_DYING. We then wait for any possible references to stop being used (i.e. epoch_wait/epoch_drain_callbacks) before we tear it fully down. However, the index in ifindex_table is not removed, so m_rcvif_restore() can still find the (now dying) interface. This results in panics, for example when dummynet restores the rcvif pointer and passes a packet to ip6_input() we can panic because the AF_INET6 domain has already been removed (so we end up dereferencing a NULL pointer there). Check that the interface is not dying before we restore it, which is equivalent to checking its presence in V_ifnet, and thus ensures that future accesses (while in NET_EPOCH) are safe. Reviewed by: glebius Sponsored by: Rubicon Communications, LLC ("Netgate") Differential Revision: https://reviews.freebsd.org/D34076
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@ -1650,11 +1650,16 @@ m_rcvif_serialize(struct mbuf *m)
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struct ifnet *
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m_rcvif_restore(struct mbuf *m)
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{
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struct ifnet *ifp;
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M_ASSERTPKTHDR(m);
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NET_EPOCH_ASSERT();
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return ((m->m_pkthdr.rcvif = ifnet_byindexgen(m->m_pkthdr.rcvidx,
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m->m_pkthdr.rcvgen)));
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ifp = ifnet_byindexgen(m->m_pkthdr.rcvidx, m->m_pkthdr.rcvgen);
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if (ifp == NULL || (ifp->if_flags & IFF_DYING))
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return (NULL);
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return (m->m_pkthdr.rcvif = ifp);
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}
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/*
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