Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933005Ab3D2VnF (ORCPT ); Mon, 29 Apr 2013 17:43:05 -0400 Received: from mail-qc0-f176.google.com ([209.85.216.176]:33235 "EHLO mail-qc0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932914Ab3D2Vmi (ORCPT ); Mon, 29 Apr 2013 17:42:38 -0400 From: Benjamin Poirier To: "David S. Miller" , Eric Dumazet , Pavel Emelyanov , Cong Wang Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v3 2/3] unix/dgram: fix peeking with an offset larger than data in queue Date: Mon, 29 Apr 2013 17:42:13 -0400 Message-Id: <1367271734-14379-2-git-send-email-bpoirier@suse.de> X-Mailer: git-send-email 1.7.10.4 In-Reply-To: <1367271734-14379-1-git-send-email-bpoirier@suse.de> References: <1367271734-14379-1-git-send-email-bpoirier@suse.de> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3634 Lines: 109 Currently, peeking on a unix datagram socket with an offset larger than len of the data in the sk receive queue returns immediately with bogus data. That's because *off is not reset between each skb_queue_walk(). This patch fixes this so that the behavior is the same as peeking with no offset on an empty queue: the caller blocks. Signed-off-by: Benjamin Poirier --- v2: address review feedback from Eric Dumazet v3: address review feedback from Cong Wang net/core/datagram.c | 21 +++++++++++++-------- 1 file changed, 13 insertions(+), 8 deletions(-) diff --git a/net/core/datagram.c b/net/core/datagram.c index 99c4f52..b5d48ac 100644 --- a/net/core/datagram.c +++ b/net/core/datagram.c @@ -78,9 +78,10 @@ static int receiver_wake_function(wait_queue_t *wait, unsigned int mode, int syn return autoremove_wake_function(wait, mode, sync, key); } /* - * Wait for a packet.. + * Wait for the last received packet to be different from skb */ -static int wait_for_packet(struct sock *sk, int *err, long *timeo_p) +static int wait_for_more_packets(struct sock *sk, int *err, long *timeo_p, + const struct sk_buff *skb) { int error; DEFINE_WAIT_FUNC(wait, receiver_wake_function); @@ -92,7 +93,7 @@ static int wait_for_packet(struct sock *sk, int *err, long *timeo_p) if (error) goto out_err; - if (!skb_queue_empty(&sk->sk_receive_queue)) + if (sk->sk_receive_queue.prev != skb) goto out; /* Socket shut down? */ @@ -131,9 +132,9 @@ out_noerr: * __skb_recv_datagram - Receive a datagram skbuff * @sk: socket * @flags: MSG_ flags + * @peeked: returns non-zero if this packet has been seen before * @off: an offset in bytes to peek skb from. Returns an offset * within an skb where data actually starts - * @peeked: returns non-zero if this packet has been seen before * @err: error code returned * * Get a datagram skbuff, understands the peeking, nonblocking wakeups @@ -161,7 +162,7 @@ out_noerr: struct sk_buff *__skb_recv_datagram(struct sock *sk, unsigned int flags, int *peeked, int *off, int *err) { - struct sk_buff *skb; + struct sk_buff *skb, *last; long timeo; /* * Caller is allowed not to check sk->sk_err before skb_recv_datagram() @@ -182,14 +183,17 @@ struct sk_buff *__skb_recv_datagram(struct sock *sk, unsigned int flags, */ unsigned long cpu_flags; struct sk_buff_head *queue = &sk->sk_receive_queue; + int _off = *off; + last = (struct sk_buff *)queue; spin_lock_irqsave(&queue->lock, cpu_flags); skb_queue_walk(queue, skb) { + last = skb; *peeked = skb->peeked; if (flags & MSG_PEEK) { - if (*off >= skb->len && (skb->len || *off || + if (_off >= skb->len && (skb->len || _off || skb->peeked)) { - *off -= skb->len; + _off -= skb->len; continue; } skb->peeked = 1; @@ -198,6 +202,7 @@ struct sk_buff *__skb_recv_datagram(struct sock *sk, unsigned int flags, __skb_unlink(skb, queue); spin_unlock_irqrestore(&queue->lock, cpu_flags); + *off = _off; return skb; } spin_unlock_irqrestore(&queue->lock, cpu_flags); @@ -207,7 +212,7 @@ struct sk_buff *__skb_recv_datagram(struct sock *sk, unsigned int flags, if (!timeo) goto no_packet; - } while (!wait_for_packet(sk, err, &timeo)); + } while (!wait_for_more_packets(sk, err, &timeo, last)); return NULL; -- 1.7.10.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/