Subject: CVE-2021-47113: btrfs: abort in rename_exchange if we fail to insert the second ref

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

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

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

btrfs: abort in rename_exchange if we fail to insert the second ref

Error injection stress uncovered a problem where we'd leave a dangling
inode ref if we failed during a rename_exchange.  This happens because
we insert the inode ref for one side of the rename, and then for the
other side.  If this second inode ref insert fails we'll leave the first
one dangling and leave a corrupt file system behind.  Fix this by
aborting if we did the insert for the first inode ref.

The Linux kernel CVE team has assigned CVE-2021-47113 to this issue.

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

	Fixed in 5.10.43 with commit 0df50d47d174
	Fixed in 5.12.10 with commit ff8de2cec65a
	Fixed in 5.13 with commit dc09ef356272

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-2021-47113
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/btrfs/inode.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/0df50d47d17401f9f140dfbe752a65e5d72f9932
	https://git.kernel.org/stable/c/ff8de2cec65a8c8521faade12a31b39c80e49f5b
	https://git.kernel.org/stable/c/dc09ef3562726cd520c8338c1640872a60187af5