net: sctp: keep owned chunk in destructor_arg instead of skb->cb
It's just silly to hold the skb destructor argument around inside skb->cb[] as we currently do in SCTP. Nowadays, we're sort of cheating on data accounting in the sense that due to commit 4c3a5bda ("sctp: Don't charge for data in sndbuf again when transmitting packet"), we orphan the skb already in the SCTP output path, i.e. giving back charged data memory, and use a different destructor only to make sure the sk doesn't vanish on skb destruction time. Thus, cb[] is still valid here as we operate within the SCTP layer. (It's generally actually a big candidate for future rework, imho.) However, storing the destructor in the cb[] can easily cause issues should an non sctp_packet_set_owner_w()'ed skb ever escape the SCTP layer, since cb[] may get overwritten by lower layers and thus can corrupt the chunk pointer. There are no such issues at present, but lets keep the chunk in destructor_arg, as this is the actual purpose for it. Signed-off-by: NDaniel Borkmann <dborkman@redhat.com> Acked-by: NVlad Yasevich <vyasevich@gmail.com> Acked-by: NNeil Horman <nhorman@tuxdriver.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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