linux-kernel - [PATCH RESEND] tipc: Reduce scope for the variable “fdefq” in tipc_link_tnl

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Message-ID: <08fe8fc3-19c3-4324-8719-0ee74b0f32c9@web.de>
Date: Sun, 2 Mar 2025 21:30:27 +0100
From: Markus Elfring <Markus.Elfring@....de>
To: kernel-janitors@...r.kernel.org, tipc-discussion@...ts.sourceforge.net,
 netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Jon Maloy <jmaloy@...hat.com>, Paolo Abeni <pabeni@...hat.com>,
 Simon Horman <horms@...nel.org>, Tuong Lien <tuong.t.lien@...tech.com.au>,
 Ying Xue <ying.xue@...driver.com>
Cc: cocci@...ia.fr, LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH RESEND] tipc: Reduce scope for the variable “fdefq” in tipc_link_tnl_prepare()

From: Markus Elfring <elfring@...rs.sourceforge.net>
Date: Thu, 13 Apr 2023 17:00:11 +0200

The address of a data structure member was determined before
a corresponding null pointer check in the implementation of
the function “tipc_link_tnl_prepare”.

Thus avoid the risk for undefined behaviour by moving the definition
for the local variable “fdefq” into an if branch at the end.

This issue was detected by using the Coccinelle software.

Fixes: 58ee86b8c775 ("tipc: adapt link failover for new Gap-ACK algorithm")
Signed-off-by: Markus Elfring <elfring@...rs.sourceforge.net>
---
 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 b3ce24823f50..5aa645e3cb35 100644
--- a/net/tipc/link.c
+++ b/net/tipc/link.c
@@ -1973,7 +1973,6 @@ void tipc_link_create_dummy_tnl_msg(struct tipc_link *l,
 void tipc_link_tnl_prepare(struct tipc_link *l, struct tipc_link *tnl,
 			   int mtyp, struct sk_buff_head *xmitq)
 {
-	struct sk_buff_head *fdefq = &tnl->failover_deferdq;
 	struct sk_buff *skb, *tnlskb;
 	struct tipc_msg *hdr, tnlhdr;
 	struct sk_buff_head *queue = &l->transmq;
@@ -2100,6 +2099,8 @@ void tipc_link_tnl_prepare(struct tipc_link *l, struct tipc_link *tnl,
 	tipc_link_xmit(tnl, &tnlq, xmitq);

 	if (mtyp == FAILOVER_MSG) {
+		struct sk_buff_head *fdefq = &tnl->failover_deferdq;
+
 		tnl->drop_point = l->rcv_nxt;
 		tnl->failover_reasm_skb = l->reasm_buf;
 		l->reasm_buf = NULL;
--
2.40.0