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From: Or Cohen <orcohen@paloaltonetworks.com>
To: netdev@vger.kernel.org, davem@davemloft.net, kuba@kernel.org,
	nixiaoming@huawei.com, matthieu.baerts@tessares.net,
	mkl@pengutronix.de, nmarkus@paloaltonetworks.com
Cc: Or Cohen <orcohen@paloaltonetworks.com>
Subject: [PATCH] net/nfc: fix use-after-free llcp_sock_bind/connect
Date: Tue,  4 May 2021 10:16:46 +0300
Message-ID: <20210504071646.28665-1-orcohen@paloaltonetworks.com> (raw)

Commits 8a4cd82d ("nfc: fix refcount leak in llcp_sock_connect()")
and c33b1cc62 ("nfc: fix refcount leak in llcp_sock_bind()")
fixed a refcount leak bug in bind/connect but introduced a
use-after-free if the same local is assigned to 2 different sockets.

This can be triggered by the following simple program:
    int sock1 = socket( AF_NFC, SOCK_STREAM, NFC_SOCKPROTO_LLCP );
    int sock2 = socket( AF_NFC, SOCK_STREAM, NFC_SOCKPROTO_LLCP );
    memset( &addr, 0, sizeof(struct sockaddr_nfc_llcp) );
    addr.sa_family = AF_NFC;
    addr.nfc_protocol = NFC_PROTO_NFC_DEP;
    bind( sock1, (struct sockaddr*) &addr, sizeof(struct sockaddr_nfc_llcp) )
    bind( sock2, (struct sockaddr*) &addr, sizeof(struct sockaddr_nfc_llcp) )
    close(sock1);
    close(sock2);

Fix this by assigning NULL to llcp_sock->local after calling
nfc_llcp_local_put.

This addresses CVE-2021-23134.

Reported-by: Or Cohen <orcohen@paloaltonetworks.com>
Reported-by: Nadav Markus <nmarkus@paloaltonetworks.com>
Fixes: c33b1cc62 ("nfc: fix refcount leak in llcp_sock_bind()")
Signed-off-by: Or Cohen <orcohen@paloaltonetworks.com>
---
 net/nfc/llcp_sock.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/nfc/llcp_sock.c b/net/nfc/llcp_sock.c
index a3b46f888803..53dbe733f998 100644
--- a/net/nfc/llcp_sock.c
+++ b/net/nfc/llcp_sock.c
@@ -109,12 +109,14 @@ static int llcp_sock_bind(struct socket *sock, struct sockaddr *addr, int alen)
 					  GFP_KERNEL);
 	if (!llcp_sock->service_name) {
 		nfc_llcp_local_put(llcp_sock->local);
+		llcp_sock->local = NULL;
 		ret = -ENOMEM;
 		goto put_dev;
 	}
 	llcp_sock->ssap = nfc_llcp_get_sdp_ssap(local, llcp_sock);
 	if (llcp_sock->ssap == LLCP_SAP_MAX) {
 		nfc_llcp_local_put(llcp_sock->local);
+		llcp_sock->local = NULL;
 		kfree(llcp_sock->service_name);
 		llcp_sock->service_name = NULL;
 		ret = -EADDRINUSE;
@@ -709,6 +711,7 @@ static int llcp_sock_connect(struct socket *sock, struct sockaddr *_addr,
 	llcp_sock->ssap = nfc_llcp_get_local_ssap(local);
 	if (llcp_sock->ssap == LLCP_SAP_MAX) {
 		nfc_llcp_local_put(llcp_sock->local);
+		llcp_sock->local = NULL;
 		ret = -ENOMEM;
 		goto put_dev;
 	}
@@ -756,6 +759,7 @@ static int llcp_sock_connect(struct socket *sock, struct sockaddr *_addr,
 sock_llcp_release:
 	nfc_llcp_put_ssap(local, llcp_sock->ssap);
 	nfc_llcp_local_put(llcp_sock->local);
+	llcp_sock->local = NULL;
 
 put_dev:
 	nfc_put_device(dev);
-- 
2.7.4


             reply index

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-04  7:16 Or Cohen [this message]
2021-05-04 19:10 ` patchwork-bot+netdevbpf
2021-05-05  4:50   ` Leon Romanovsky
  -- strict thread matches above, loose matches on Subject: below --
2021-05-04  7:15 Or Cohen
2021-05-04  8:12 ` Leon Romanovsky
2021-05-04 16:01   ` Or Cohen
2021-05-05  4:46     ` Leon Romanovsky
     [not found]       ` <CABV_C9OJ6v1deEknc+V3cJaT+CPjmzg6Wb06_Rsey3AXqOBNYg@mail.gmail.com>
2021-05-05 11:30         ` Nadav Markus
2021-05-05 11:39         ` Leon Romanovsky
     [not found]           ` <CABV_C9PscjqNPTbK0JuNGsgCAX-xYg9=GG1KNyOh3hQU1TuzWQ@mail.gmail.com>
2021-05-05 14:17             ` Leon Romanovsky
2021-05-05 14:31               ` Or Cohen

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