Subject: CVE-2021-47240: net: qrtr: fix OOB Read in qrtr_endpoint_post

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

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

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

net: qrtr: fix OOB Read in qrtr_endpoint_post

Syzbot reported slab-out-of-bounds Read in
qrtr_endpoint_post. The problem was in wrong
_size_ type:

	if (len != ALIGN(size, 4) + hdrlen)
		goto err;

If size from qrtr_hdr is 4294967293 (0xfffffffd), the result of
ALIGN(size, 4) will be 0. In case of len == hdrlen and size == 4294967293
in header this check won't fail and

	skb_put_data(skb, data + hdrlen, size);

will read out of bound from data, which is hdrlen allocated block.

The Linux kernel CVE team has assigned CVE-2021-47240 to this issue.

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

	Issue introduced in 4.15 with commit 194ccc88297a and fixed in 4.19.196 with commit f8111c0d7ed4
	Issue introduced in 4.15 with commit 194ccc88297a and fixed in 5.4.128 with commit 26b8d10703a9
	Issue introduced in 4.15 with commit 194ccc88297a and fixed in 5.10.46 with commit 960b08dd36de
	Issue introduced in 4.15 with commit 194ccc88297a and fixed in 5.12.13 with commit 19892ab9c9d8
	Issue introduced in 4.15 with commit 194ccc88297a and fixed in 5.13 with commit ad9d24c9429e

Please see https://www.kernel.org for 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-2021-47240
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/qrtr/qrtr.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/f8111c0d7ed42ede41a3d0d393b104de0730a8a6
	https://git.kernel.org/stable/c/26b8d10703a9be45d6097946b2b4011f7dd2c56f
	https://git.kernel.org/stable/c/960b08dd36de1e341e3eb43d1c547513e338f4f8
	https://git.kernel.org/stable/c/19892ab9c9d838e2e5a7744d36e4bb8b7c3292fe
	https://git.kernel.org/stable/c/ad9d24c9429e2159d1e279dc3a83191ccb4daf1d