CVE-2021-47068

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

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-2021-2313

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References