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Date: Thu, 29 Feb 2024 23:38:05 +0100
From: Greg Kroah-Hartman <>
Cc: Greg Kroah-Hartman <>
Subject: CVE-2021-47068: net/nfc: fix use-after-free llcp_sock_bind/connect


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) )

Fix this by assigning NULL to llcp_sock->local after calling

This addresses CVE-2021-23134.

The Linux kernel CVE team has assigned CVE-2021-47068 to this issue.

Affected and fixed versions

	Issue introduced in 4.4.267 with commit a1cdd18c49d2 and fixed in 4.4.269 with commit 26157c82ba75
	Issue introduced in 4.9.267 with commit 18013007b596 and fixed in 4.9.269 with commit ccddad6dd285
	Issue introduced in 4.14.231 with commit 538a6ff11516 and fixed in 4.14.233 with commit 18ae4a192a44
	Issue introduced in 4.19.187 with commit adbb1d218c5f and fixed in 4.19.191 with commit 48fba458fe54
	Issue introduced in 5.4.112 with commit c89903c9eff2 and fixed in 5.4.119 with commit e32352070bca
	Issue introduced in 5.10.30 with commit 6fb003e5ae18 and fixed in 5.10.37 with commit 6b7021ed36da
	Issue introduced in 5.11.14 with commit 8c9e4971e142 and fixed in 5.11.21 with commit 374cdde4dcc9
	Issue introduced in 5.12 with commit c33b1cc62 and fixed in 5.12.4 with commit 18175fe17ae0
	Issue introduced in 5.12 with commit c33b1cc62 and fixed in 5.13 with commit c61760e6940d

Please see or a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files

The file(s) affected by this issue are:


The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:

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