Commit 45c8b7b1 authored Oct 19, 2015 by Jon Paul Maloy Committed by David S. Miller Oct 21, 2015

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 d0f91938 ("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 d0f91938 ("tipc: add ip/udp media type")
Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 1241365f

net/tipc/msg.c

+9 −3

Original line number	Diff line number	Diff line
		@@ -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;
		}

Admin message