From 45c8b7b175ceb2d542e0fe15247377bf3bce29ec Mon Sep 17 00:00:00 2001 From: Jon Paul Maloy Date: Mon, 19 Oct 2015 11:33:00 -0400 Subject: [PATCH] tipc: allow non-linear first fragment buffer The current code for message reassembly is erroneously assuming that the the first arriving fragment buffer always is linear, and then goes ahead resetting the fragment list of that buffer in anticipation of more arriving fragments. However, if the buffer already happens to be non-linear, we will inadvertently drop the already attached fragment list, and later on trig a BUG() in __pskb_pull_tail(). We see this happen when running fragmented TIPC multicast across UDP, something made possible since commit d0f91938bede ("tipc: add ip/udp media type") We fix this by not resetting the fragment list when the buffer is non- linear, and by initiatlizing our private fragment list tail pointer to the tail of the existing fragment list. Fixes: commit d0f91938bede ("tipc: add ip/udp media type") Signed-off-by: Jon Maloy Signed-off-by: David S. Miller --- net/tipc/msg.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/net/tipc/msg.c b/net/tipc/msg.c index c5ac436235e0..5f73450159df 100644 --- a/net/tipc/msg.c +++ b/net/tipc/msg.c @@ -121,7 +121,7 @@ int tipc_buf_append(struct sk_buff **headbuf, struct sk_buff **buf) { struct sk_buff *head = *headbuf; struct sk_buff *frag = *buf; - struct sk_buff *tail; + struct sk_buff *tail = NULL; struct tipc_msg *msg; u32 fragid; int delta; @@ -141,9 +141,15 @@ int tipc_buf_append(struct sk_buff **headbuf, struct sk_buff **buf) if (unlikely(skb_unclone(frag, GFP_ATOMIC))) goto err; head = *headbuf = frag; - skb_frag_list_init(head); - TIPC_SKB_CB(head)->tail = NULL; *buf = NULL; + TIPC_SKB_CB(head)->tail = NULL; + if (skb_is_nonlinear(head)) { + skb_walk_frags(head, tail) { + TIPC_SKB_CB(head)->tail = tail; + } + } else { + skb_frag_list_init(head); + } return 0; } -- 2.34.1