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> Signed-off-by: Yang Yingliang <yangyingliang@huawei.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 bc269e83e1e55..59de4f54dd18c 100644 --- a/net/nfc/llcp_sock.c +++ b/net/nfc/llcp_sock.c @@ -121,12 +121,14 @@ 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; @@ -721,6 +723,7 @@ 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; } @@ -759,6 +762,7 @@ static int llcp_sock_connect(struct socket *sock, struct sockaddr *_addr, sock_unlink: nfc_llcp_put_ssap(local, llcp_sock->ssap); nfc_llcp_local_put(llcp_sock->local); + llcp_sock->local = NULL; nfc_llcp_sock_unlink(&local->connecting_sockets, sk); kfree(llcp_sock->service_name); -- 2.25.1