Messages in this thread Patch in this message | | | Date | Wed, 6 Jan 2010 00:07:46 +0100 | From | Jarek Poplawski <> | Subject | [PATCH] af_packet: Don't use skb after dev_queue_xmit() |
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David Miller wrote, On 12/27/2009 05:11 AM:
> From: David Miller <davem@davemloft.net> > Date: Sat, 26 Dec 2009 19:44:18 -0800 (PST) > >> From: Stephen Hemminger <shemminger@linux-foundation.org> >> Date: Sat, 26 Dec 2009 14:05:44 -0800 >> >>> Other drivers may have same problem, I really think this ought >>> to be done at higher level. >> I tend to agree with you, and I thought we had handled all >> cases. Let's simply make AF_PACKET linearize the link >> level header before sending things out to the transmit path. >> >> I can work on this if you want. > > Actually Stephen, I took a look and I can't see how AF_PACKET > can create this situation. > > It always copies into the linear area of the SKB it allocates > for sendmsg() processing. Whether the data comes from sendmsg > data or the mmap() ring buffer.
Actually, I think there is a bug in this place, but of course this might be unconnected. Anyway, Michael, could you try this patch? BTW, did you try with CONFIG_PACKET_MMAP disabled?
Thanks, Jarek P. ----------------->
Changing an skb after dev_queue_xmit() is illegal. And since it's inconsistent to treat specially net_xmit_errno() non-zero return, while ignoring other dev_queue_xmit() errors, there is no reason to break the loop in tpacket_snd() in this case.
With debugging by: Stephen Hemminger <shemminger@linux-foundation.org>
Reported-by: Michael Breuer <mbreuer@majjas.com> Signed-off-by: Jarek Poplawski <jarkao2@gmail.com> ---
net/packet/af_packet.c | 8 +++----- 1 files changed, 3 insertions(+), 5 deletions(-)
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index e0516a2..984a1fa 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -1021,8 +1021,9 @@ static int tpacket_snd(struct packet_sock *po, struct msghdr *msg) status = TP_STATUS_SEND_REQUEST; err = dev_queue_xmit(skb); - if (unlikely(err > 0 && (err = net_xmit_errno(err)) != 0)) - goto out_xmit; + if (unlikely(err > 0)) + err = net_xmit_errno(err); + packet_increment_head(&po->tx_ring); len_sum += tp_len; } while (likely((ph != NULL) || @@ -1033,9 +1034,6 @@ static int tpacket_snd(struct packet_sock *po, struct msghdr *msg) err = len_sum; goto out_put; -out_xmit: - skb->destructor = sock_wfree; - atomic_dec(&po->tx_ring.pending); out_status: __packet_set_status(po, ph, status); kfree_skb(skb);
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