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tipc: fix bug in broadcast retransmit code

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In commit 58dc55f256 ("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 <ying.xue@windriver.com>
Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jon Maloy 2015-01-09 15:26:58 +08:00 committed by David S. Miller
parent 45e81834a4
commit 703068eee6
1 changed files with 3 additions and 2 deletions
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5
net/tipc/bcast.c
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@ -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));
}
/**