diff options
author | Soheil Hassas Yeganeh <soheil@google.com> | 2016-11-03 18:24:27 -0400 |
---|---|---|
committer | David S. Miller <davem@davemloft.net> | 2016-11-07 20:29:10 -0500 |
commit | f5f99309fa7481f59a500f0d08f3379cd6424c1f (patch) | |
tree | b1de394448ccd8c4851be4183f9d7f92aa319e35 | |
parent | 5f7f75027f89b741a977db730abd66695fe75f2d (diff) |
sock: do not set sk_err in sock_dequeue_err_skb
Do not set sk_err when dequeuing errors from the error queue.
Doing so results in:
a) Bugs: By overwriting existing sk_err values, it possibly
hides legitimate errors. It is also incorrect when local
errors are queued with ip_local_error. That happens in the
context of a system call, which already returns the error
code.
b) Inconsistent behavior: When there are pending errors on
the error queue, sk_err is sometimes 0 (e.g., for
the first timestamp on the error queue) and sometimes
set to an error code (after dequeuing the first
timestamp).
c) Suboptimality: Setting sk_err to ENOMSG on simple
TX timestamps can abort parallel reads and writes.
Removing this line doesn't break userspace. This is because
userspace code cannot rely on sk_err for detecting whether
there is something on the error queue. Except for ICMP messages
received for UDP and RAW, sk_err is not set at enqueue time,
and as a result sk_err can be 0 while there are plenty of
errors on the error queue.
For ICMP packets in UDP and RAW, sk_err is set when they are
enqueued on the error queue, but that does not result in aborting
reads and writes. For such cases, sk_err is only readable via
getsockopt(SO_ERROR) which will reset the value of sk_err on
its own. More importantly, prior to this patch,
recvmsg(MSG_ERRQUEUE) has a race on setting sk_err (i.e.,
sk_err is set by sock_dequeue_err_skb without atomic ops or
locks) which can store 0 in sk_err even when we have ICMP
messages pending. Removing this line from sock_dequeue_err_skb
eliminates that race.
Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r-- | net/core/skbuff.c | 1 |
1 files changed, 0 insertions, 1 deletions
diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 1e3e0087245b..0b2a6e94af2d 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -3725,7 +3725,6 @@ struct sk_buff *sock_dequeue_err_skb(struct sock *sk) err = SKB_EXT_ERR(skb_next)->ee.ee_errno; spin_unlock_irqrestore(&q->lock, flags); - sk->sk_err = err; if (err) sk->sk_error_report(sk); |