CVE-2026-68422: btrfs: fix root leak if its reloc root is unexpected in merge_reloc_roots()

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

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

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

btrfs: fix root leak if its reloc root is unexpected in merge_reloc_roots()

If we have an unexpected reloc_root for our root, we jump to the out label
but never drop the reference we obtained for root, resulting in a leak.
Add a missing btrfs_put_root() call.

The Linux kernel CVE team has assigned CVE-2026-68422 to this issue.


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

	Issue introduced in 5.13 with commit 24213fa46c7080c31d79aa2e3e2f0d9480cab700 and fixed in 6.6.148 with commit b3d39b03799600c76c33486e2d29b73a771023db
	Issue introduced in 5.13 with commit 24213fa46c7080c31d79aa2e3e2f0d9480cab700 and fixed in 6.12.101 with commit 72f673d1c1deb819554d3e7e154f6d84301eb735
	Issue introduced in 5.13 with commit 24213fa46c7080c31d79aa2e3e2f0d9480cab700 and fixed in 6.18.42 with commit 60a23d4ea169e27403f3bb023bb98036797c0206
	Issue introduced in 5.13 with commit 24213fa46c7080c31d79aa2e3e2f0d9480cab700 and fixed in 7.1.6 with commit 7591d1727067d6063247901ad25c4bdc4e5695c4
	Issue introduced in 5.13 with commit 24213fa46c7080c31d79aa2e3e2f0d9480cab700 and fixed in 7.2-rc4 with commit ce6050bafb4e33377dc17fcc357736bfc351180c

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-2026-68422
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/relocation.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/b3d39b03799600c76c33486e2d29b73a771023db
	https://git.kernel.org/stable/c/72f673d1c1deb819554d3e7e154f6d84301eb735
	https://git.kernel.org/stable/c/60a23d4ea169e27403f3bb023bb98036797c0206
	https://git.kernel.org/stable/c/7591d1727067d6063247901ad25c4bdc4e5695c4
	https://git.kernel.org/stable/c/ce6050bafb4e33377dc17fcc357736bfc351180c