From 164167794c1f9f34264e3d9281385728b0d22018 Mon Sep 17 00:00:00 2001 From: Jon Paul Maloy Date: Thu, 8 Jan 2015 12:27:27 -0500 Subject: [PATCH] tipc: fix bug in broadcast retransmit code In commit 58dc55f25631178ee74cd27185956a8f7dcb3e32 ("tipc: use generic SKB list APIs to manage link transmission queue") we replace all list traversal loops with the macros skb_queue_walk() or skb_queue_walk_safe(). While the previous loops were based on the assumption that the list was NULL-terminated, the standard macros stop when the iterator reaches the list head, which is non-NULL. In the function bclink_retransmit_pkt() this macro replacement has lead to a bug. When we receive a BCAST STATE_MSG we unconditionally call the function bclink_retransmit_pkt(), whether there really is anything to retransmit or not, assuming that the sequence number comparisons will lead to the correct behavior. However, if the transmission queue is empty, or if there are no eligible buffers in the transmission queue, we will by mistake pass the list head pointer to the function tipc_link_retransmit(). Since the list head is not a valid sk_buff, this leads to a crash. In this commit we fix this by only calling tipc_link_retransmit() if we actually found eligible buffers in the transmission queue. Reviewed-by: Ying Xue Signed-off-by: Jon Maloy Signed-off-by: David S. Miller --- net/tipc/bcast.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/net/tipc/bcast.c b/net/tipc/bcast.c index 96ceefeb9daf..a9e174fc0f91 100644 --- a/net/tipc/bcast.c +++ b/net/tipc/bcast.c @@ -220,10 +220,11 @@ static void bclink_retransmit_pkt(u32 after, u32 to) struct sk_buff *skb; skb_queue_walk(&bcl->outqueue, skb) { - if (more(buf_seqno(skb), after)) + if (more(buf_seqno(skb), after)) { + tipc_link_retransmit(bcl, skb, mod(to - after)); break; + } } - tipc_link_retransmit(bcl, skb, mod(to - after)); } /** -- 2.20.1