Subject: CVE-2021-47115: nfc: fix NULL ptr dereference in llcp_sock_getname() after failed connect

From: Greg Kroah-Hartman <[email-masked]>

Description
===========

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

nfc: fix NULL ptr dereference in llcp_sock_getname() after failed connect

It's possible to trigger NULL pointer dereference by local unprivileged
user, when calling getsockname() after failed bind() (e.g. the bind
fails because LLCP_SAP_MAX used as SAP):

  BUG: kernel NULL pointer dereference, address: 0000000000000000
  CPU: 1 PID: 426 Comm: llcp_sock_getna Not tainted 5.13.0-rc2-next-20210521+ #9
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-1 04/01/2014
  Call Trace:
   llcp_sock_getname+0xb1/0xe0
   __sys_getpeername+0x95/0xc0
   ? lockdep_hardirqs_on_prepare+0xd5/0x180
   ? syscall_enter_from_user_mode+0x1c/0x40
   __x64_sys_getpeername+0x11/0x20
   do_syscall_64+0x36/0x70
   entry_SYSCALL_64_after_hwframe+0x44/0xae

This can be reproduced with Syzkaller C repro (bind followed by
getpeername):
https://syzkaller.appspot.com/x/repro.c?x=14def446e00000

The Linux kernel CVE team has assigned CVE-2021-47115 to this issue.

Affected and fixed versions
===========================

	Issue introduced in 3.3 with commit d646960f7986 and fixed in 4.4.272 with commit eb6875d48590
	Issue introduced in 3.3 with commit d646960f7986 and fixed in 4.9.272 with commit 39c15bd2e5d1
	Issue introduced in 3.3 with commit d646960f7986 and fixed in 4.14.236 with commit ffff05b9ee5c
	Issue introduced in 3.3 with commit d646960f7986 and fixed in 4.19.194 with commit 93e4ac2a9979
	Issue introduced in 3.3 with commit d646960f7986 and fixed in 5.4.125 with commit 5d4c4b06ed9f
	Issue introduced in 3.3 with commit d646960f7986 and fixed in 5.10.43 with commit 48ee0db61c82
	Issue introduced in 3.3 with commit d646960f7986 and fixed in 5.12.10 with commit 0c4559736d9a
	Issue introduced in 3.3 with commit d646960f7986 and fixed in 5.13 with commit 4ac06a1e013c

Please see https://www.kernel.org 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
	https://cve.org/CVERecord/?id=CVE-2021-47115
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:
	net/nfc/llcp_sock.c

Mitigation
==========

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:
	https://git.kernel.org/stable/c/eb6875d48590d8e564092e831ff07fa384d7e477
	https://git.kernel.org/stable/c/39c15bd2e5d11bcf7f4c3dba2aad9e1e110a5d94
	https://git.kernel.org/stable/c/ffff05b9ee5c74c04bba2801c1f99b31975d74d9
	https://git.kernel.org/stable/c/93e4ac2a9979a9a4ecc158409ed9c3044dc0ae1f
	https://git.kernel.org/stable/c/5d4c4b06ed9fb7a69d0b2e2a73fc73226d25ab70
	https://git.kernel.org/stable/c/48ee0db61c8299022ec88c79ad137f290196cac2
	https://git.kernel.org/stable/c/0c4559736d9a4ec1ca58ba98ca34e7c4da4c422b
	https://git.kernel.org/stable/c/4ac06a1e013cf5fdd963317ffd3b968560f33bba