linux-kernel - [PATCH v2 2/8] af_packet: avoid erroring out after sock_init_data() in packet

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Message-Id: <20241007213502.28183-3-ignat@cloudflare.com>
Date: Mon,  7 Oct 2024 22:34:56 +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 v2 2/8] af_packet: avoid erroring out after sock_init_data() in packet_create()

After sock_init_data() the allocated sk object is attached to the provided
sock object. On error, packet_create() frees the sk object leaving the
dangling pointer in the sock object on return. Some other code may try
to use this pointer and cause use-after-free.

Suggested-by: Eric Dumazet <edumazet@...gle.com>
Signed-off-by: Ignat Korchagin <ignat@...udflare.com>
---
 net/packet/af_packet.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index a705ec214254..97774bd4b6cb 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -3421,17 +3421,17 @@ static int packet_create(struct net *net, struct socket *sock, int protocol,
 	if (sock->type == SOCK_PACKET)
 		sock->ops = &packet_ops_spkt;
 
+	po = pkt_sk(sk);
+	err = packet_alloc_pending(po);
+	if (err)
+		goto out_sk_free;
+
 	sock_init_data(sock, sk);
 
-	po = pkt_sk(sk);
 	init_completion(&po->skb_completion);
 	sk->sk_family = PF_PACKET;
 	po->num = proto;
 
-	err = packet_alloc_pending(po);
-	if (err)
-		goto out2;
-
 	packet_cached_dev_reset(po);
 
 	sk->sk_destruct = packet_sock_destruct;
@@ -3463,7 +3463,7 @@ static int packet_create(struct net *net, struct socket *sock, int protocol,
 	sock_prot_inuse_add(net, &packet_proto, 1);
 
 	return 0;
-out2:
+out_sk_free:
 	sk_free(sk);
 out:
 	return err;
-- 
2.39.5