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net/nfc: fix use-after-free llcp_sock_bind/connect 

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>
This commit is contained in:
Or Cohen 2021-05-04 10:16:46 +03:00 committed by David S. Miller
parent 8d432592f3
commit c61760e694
1 changed files with 4 additions and 0 deletions
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4
net/nfc/llcp_sock.c
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@ -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);