netdev - [PATCH net] tipc: fix message corruption bug for deferred packets

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Message-ID: <1392115106-16178-1-git-send-email-erik.hugne@ericsson.com>
Date:	Tue, 11 Feb 2014 11:38:26 +0100
From:	<erik.hugne@...csson.com>
To:	<netdev@...r.kernel.org>, <jon.maloy@...csson.com>
CC:	<ying.xue@...driver.com>, <paul.gortmaker@...driver.com>,
	<tipc-discussion@...ts.sourceforge.net>,
	Erik Hugne <erik.hugne@...csson.com>
Subject: [PATCH net] tipc: fix message corruption bug for deferred packets

From: Erik Hugne <erik.hugne@...csson.com>

If a packet received on a link is out-of-sequence, it will be
placed on a deferred queue and later reinserted in the receive
path once the preceding packets have been processed. The problem
with this is that it will be subject to the buffer adjustment from
link_recv_buf_validate twice. The second adjustment for 20 bytes
header space will corrupt the packet.

We solve this by tagging the deferred packets and bail out from
receive buffer validation for packets that have already been
subjected to this.

Signed-off-by: Erik Hugne <erik.hugne@...csson.com>
Reviewed-by: Jon Maloy <jon.maloy@...csson.com>
---

This was found in a 12 node cluster with hundreds to thousands of
publications on each node. When a node came alive after a reboot,
each node redistributed their publications in 5-10 NAME_DISTRIBUTOR
messages. The bundled publications where sometimes corrupted on the
receiver side. It was always the last 20 bytes of the payload, and
further tracing showed that the corruption was isolated to messages
that had once been deferred. However the corruption applies to
_all_ deferred traffic.

 net/tipc/core.h |    1 +
 net/tipc/link.c |    7 +++++++
 2 files changed, 8 insertions(+)

diff --git a/net/tipc/core.h b/net/tipc/core.h
index 1ff477b..5569d96 100644
--- a/net/tipc/core.h
+++ b/net/tipc/core.h
@@ -192,6 +192,7 @@ static inline void k_term_timer(struct timer_list *timer)

 struct tipc_skb_cb {
 	void *handle;
+	bool deferred;
 };

 #define TIPC_SKB_CB(__skb) ((struct tipc_skb_cb *)&((__skb)->cb[0]))
diff --git a/net/tipc/link.c b/net/tipc/link.c
index d4b5de4..da6018b 100644
--- a/net/tipc/link.c
+++ b/net/tipc/link.c
@@ -1391,6 +1391,12 @@ static int link_recv_buf_validate(struct sk_buff *buf)
 	u32 hdr_size;
 	u32 min_hdr_size;

+	/* If this packet comes from the defer queue, the skb has already
+	 * been validated
+	 */
+	if (unlikely(TIPC_SKB_CB(buf)->deferred))
+		return 1;
+
 	if (unlikely(buf->len < MIN_H_SIZE))
 		return 0;

@@ -1703,6 +1709,7 @@ static void link_handle_out_of_seq_msg(struct tipc_link *l_ptr,
 				&l_ptr->newest_deferred_in, buf)) {
 		l_ptr->deferred_inqueue_sz++;
 		l_ptr->stats.deferred_recv++;
+		TIPC_SKB_CB(buf)->deferred = true;
 		if ((l_ptr->deferred_inqueue_sz % 16) == 1)
 			tipc_link_send_proto_msg(l_ptr, STATE_MSG, 0, 0, 0, 0, 0);
 	} else
-- 
1.7.9.5

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