netdev - [PATCH] tipc: fix dereference before check warning

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Date:	Wed, 13 Nov 2013 09:35:11 +0100
From:	<erik.hugne@...csson.com>
To:	<jon.maloy@...csson.com>, <paul.gortmaker@...driver.com>,
	<dan.carpenter@...cle.com>, <maloy@...jonn.com>,
	<netdev@...r.kernel.org>
CC:	<tipc-discussion@...ts.sourceforge.net>, <ying.xue@...driver.com>,
	Erik Hugne <erik.hugne@...csson.com>
Subject: [PATCH] tipc: fix dereference before check warning

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

This fixes the following Smatch warning:
net/tipc/link.c:2364 tipc_link_recv_fragment()
    warn: variable dereferenced before check '*head' (see line 2361)

A null pointer might be passed to skb_try_coalesce if
a malicious sender injects orphan fragments on a link.

Signed-off-by: Erik Hugne <erik.hugne@...csson.com>
---
 net/tipc/link.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/tipc/link.c b/net/tipc/link.c
index cf465d6..69cd9bf 100644
--- a/net/tipc/link.c
+++ b/net/tipc/link.c
@@ -2358,7 +2358,8 @@ int tipc_link_recv_fragment(struct sk_buff **head, struct sk_buff **tail,
 		*head = frag;
 		skb_frag_list_init(*head);
 		return 0;
-	} else if (skb_try_coalesce(*head, frag, &headstolen, &delta)) {
+	} else if (*head &&
+		   skb_try_coalesce(*head, frag, &headstolen, &delta)) {
 		kfree_skb_partial(frag, headstolen);
 	} else {
 		if (!*head)
-- 
1.7.9.5

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