Subject: CVE-2021-47123: io_uring: fix ltout double free on completion race

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

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

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

io_uring: fix ltout double free on completion race

Always remove linked timeout on io_link_timeout_fn() from the master
request link list, otherwise we may get use-after-free when first
io_link_timeout_fn() puts linked timeout in the fail path, and then
will be found and put on master's free.

The Linux kernel CVE team has assigned CVE-2021-47123 to this issue.

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

	Issue introduced in 5.11 with commit 90cd7e424969 and fixed in 5.12.10 with commit 1f64f5e903b9
	Issue introduced in 5.11 with commit 90cd7e424969 and fixed in 5.13 with commit 447c19f3b507

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-2021-47123
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:
	fs/io_uring.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/1f64f5e903b9d1d157875721e02adadc9d6f0a5d
	https://git.kernel.org/stable/c/447c19f3b5074409c794b350b10306e1da1ef4ba