linux-kernel - [RFC PATCH 07/13] udp_tunnel: remove the usage of the list iterator after the loop

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Message-Id: <20220217184829.1991035-8-jakobkoschel@gmail.com>
Date:   Thu, 17 Feb 2022 19:48:23 +0100
From:   Jakob Koschel <jakobkoschel@...il.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-kernel@...r.kernel.org
Cc:     linux-arch@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Arnd Bergman <arnd@...db.de>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Kees Cook <keescook@...omium.org>,
        Mike Rapoport <rppt@...nel.org>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Brian Johannesmeyer <bjohannesmeyer@...il.com>,
        Cristiano Giuffrida <c.giuffrida@...nl>,
        "Bos, H.J." <h.j.bos@...nl>, Jakob Koschel <jakobkoschel@...il.com>
Subject: [RFC PATCH 07/13] udp_tunnel: remove the usage of the list iterator after the loop

The usage of node->dev after the loop body is a legitimate type
confusion if the break was not hit. It will compare an undefined
memory location with dev that could potentially be equal. The value
of node->dev in this case could either be a random struct member of the
head element or an out-of-bounds value.

Therefore it is more safe to use the found variable. With the
introduction of speculative safe list iterator this check could be
replaced with if (!node).

Signed-off-by: Jakob Koschel <jakobkoschel@...il.com>
---
 net/ipv4/udp_tunnel_nic.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/udp_tunnel_nic.c b/net/ipv4/udp_tunnel_nic.c
index b91003538d87..c47f9fb36d29 100644
--- a/net/ipv4/udp_tunnel_nic.c
+++ b/net/ipv4/udp_tunnel_nic.c
@@ -842,11 +842,14 @@ udp_tunnel_nic_unregister(struct net_device *dev, struct udp_tunnel_nic *utn)
 	 */
 	if (info->shared) {
 		struct udp_tunnel_nic_shared_node *node, *first;
+		bool found = false;
 
 		list_for_each_entry(node, &info->shared->devices, list)
-			if (node->dev == dev)
+			if (node->dev == dev) {
+				found = true;
 				break;
-		if (node->dev != dev)
+			}
+		if (!found)
 			return;
 
 		list_del(&node->list);
-- 
2.25.1