netdev - [PATCH net-next v3 8/9] net: warn, if pf->create does not clear sock->sk on error

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Message-Id: <20241014153808.51894-9-ignat@cloudflare.com>
Date: Mon, 14 Oct 2024 16:38:07 +0100
From: Ignat Korchagin <ignat@...udflare.com>
To: "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Marcel Holtmann <marcel@...tmann.org>,
	Johan Hedberg <johan.hedberg@...il.com>,
	Luiz Augusto von Dentz <luiz.dentz@...il.com>,
	Oliver Hartkopp <socketcan@...tkopp.net>,
	Marc Kleine-Budde <mkl@...gutronix.de>,
	Alexander Aring <alex.aring@...il.com>,
	Stefan Schmidt <stefan@...enfreihafen.org>,
	Miquel Raynal <miquel.raynal@...tlin.com>,
	David Ahern <dsahern@...nel.org>,
	Willem de Bruijn <willemdebruijn.kernel@...il.com>,
	linux-bluetooth@...r.kernel.org,
	linux-can@...r.kernel.org,
	linux-wpan@...r.kernel.org
Cc: kernel-team@...udflare.com,
	kuniyu@...zon.com,
	alibuda@...ux.alibaba.com,
	Ignat Korchagin <ignat@...udflare.com>
Subject: [PATCH net-next v3 8/9] net: warn, if pf->create does not clear sock->sk on error

All pf->create implementations have been fixed now to clear sock->sk on
error, when they deallocate the allocated sk object.

Put a warning in place to make sure we don't break this promise in the
future.

Suggested-by: Kuniyuki Iwashima <kuniyu@...zon.com>
Signed-off-by: Ignat Korchagin <ignat@...udflare.com>
---
 net/socket.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/socket.c b/net/socket.c
index 24b404299015..9a8e4452b9b2 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -1576,9 +1576,9 @@ int __sock_create(struct net *net, int family, int type, int protocol,
 	err = pf->create(net, sock, protocol, kern);
 	if (err < 0) {
 		/* ->create should release the allocated sock->sk object on error
-		 * but it may leave the dangling pointer
+		 * and make sure sock->sk is set to NULL to avoid use-after-free
 		 */
-		sock->sk = NULL;
+		DEBUG_NET_WARN_ON_ONCE(sock->sk);
 		goto out_module_put;
 	}
 
-- 
2.39.5