[PATCH 5.11 003/601] net/nfc: fix use-after-free llcp_sock_bind/connect

Greg Kroah-Hartman
2021-05-12T16:53:36Z

From: Or Cohen <orcohen@paloaltonetworks.com>

commit c61760e6940dd4039a7f5e84a6afc9cdbf4d82b6 upstream.

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>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/nfc/llcp_sock.c | 4 ++++
1 file changed, 4 insertions(+)

--- a/net/nfc/llcp_sock.c
+++ b/net/nfc/llcp_sock.c
@@ -109,12 +109,14 @@ static int llcp_sock_bind(struct socket
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 sock
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 @@ sock_unlink:
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);