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| author | Daniel Borkmann <dborkman@redhat.com> | 2014-11-20 01:54:48 +0100 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2014-11-21 14:46:12 -0500 |
| commit | f869c912869edc2754355af9e10e5aaff8ff5a40 (patch) | |
| tree | e70a9e95f1b235903f50821d8c9f3a0dd7842fda /net/sctp | |
| parent | 44c8bc3ce39f4cbeb7bf13162666fb6d0aad864d (diff) | |
| download | linux-f869c912869edc2754355af9e10e5aaff8ff5a40.tar.gz linux-f869c912869edc2754355af9e10e5aaff8ff5a40.tar.bz2 linux-f869c912869edc2754355af9e10e5aaff8ff5a40.zip | |
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 4c3a5bdae293 ("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: Daniel Borkmann <dborkman@redhat.com>
Acked-by: Vlad Yasevich <vyasevich@gmail.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/sctp')
| -rw-r--r-- | net/sctp/socket.c | 12 |
1 files changed, 4 insertions, 8 deletions
diff --git a/net/sctp/socket.c b/net/sctp/socket.c index 2120292c842d..85e0b653edd7 100644 --- a/net/sctp/socket.c +++ b/net/sctp/socket.c @@ -162,7 +162,7 @@ static inline void sctp_set_owner_w(struct sctp_chunk *chunk) chunk->skb->destructor = sctp_wfree; /* Save the chunk pointer in skb for sctp_wfree to use later. */ - *((struct sctp_chunk **)(chunk->skb->cb)) = chunk; + skb_shinfo(chunk->skb)->destructor_arg = chunk; asoc->sndbuf_used += SCTP_DATA_SNDSIZE(chunk) + sizeof(struct sk_buff) + @@ -6870,14 +6870,10 @@ static void sctp_wake_up_waiters(struct sock *sk, */ static void sctp_wfree(struct sk_buff *skb) { - struct sctp_association *asoc; - struct sctp_chunk *chunk; - struct sock *sk; + struct sctp_chunk *chunk = skb_shinfo(skb)->destructor_arg; + struct sctp_association *asoc = chunk->asoc; + struct sock *sk = asoc->base.sk; - /* Get the saved chunk pointer. */ - chunk = *((struct sctp_chunk **)(skb->cb)); - asoc = chunk->asoc; - sk = asoc->base.sk; asoc->sndbuf_used -= SCTP_DATA_SNDSIZE(chunk) + sizeof(struct sk_buff) + sizeof(struct sctp_chunk); |