From: Cengiz Can <cengiz@kernel.wtf>
Date: Mon, 7 Dec 2020 08:14:24 +0000 (+0300)
Subject: net: tipc: prevent possible null deref of link
X-Git-Tag: v5.9.16~18
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4dd9051068f536453e7e8fedc7c6cc873a0910d7;p=thirdparty%2Fkernel%2Fstable.git

net: tipc: prevent possible null deref of link

[ Upstream commit 0398ba9e5a4b5675aa571e0445689d3c2e499c2d ]

`tipc_node_apply_property` does a null check on a `tipc_link_entry`
pointer but also accesses the same pointer out of the null check block.

This triggers a warning on Coverity Static Analyzer because we're
implying that `e->link` can BE null.

Move "Update MTU for node link entry" line into if block to make sure
that we're not in a state that `e->link` is null.

Signed-off-by: Cengiz Can <cengiz@kernel.wtf>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/net/tipc/node.c b/net/tipc/node.c
index 8c9c12072a784..052c41cec89b4 100644
--- a/net/tipc/node.c
+++ b/net/tipc/node.c
@@ -2170,9 +2170,11 @@ void tipc_node_apply_property(struct net *net, struct tipc_bearer *b,
 							&xmitq);
 			else if (prop == TIPC_NLA_PROP_MTU)
 				tipc_link_set_mtu(e->link, b->mtu);
+
+			/* Update MTU for node link entry */
+			e->mtu = tipc_link_mss(e->link);
 		}
-		/* Update MTU for node link entry */
-		e->mtu = tipc_link_mss(e->link);
+
 		tipc_node_write_unlock(n);
 		tipc_bearer_xmit(net, bearer_id, &xmitq, &e->maddr, NULL);
 	}