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

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