CVE-2026-43358: btrfs: add missing RCU unlock in error path in try_release_subpage_extent_buffer()

CVE-2026-43358: btrfs: add missing RCU unlock in error path in try_release_subpage_extent_buffer()

[Greg Kroah-Hartman]

From: Greg Kroah-Hartman <gregkh@kernel.org>

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

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

btrfs: add missing RCU unlock in error path in try_release_subpage_extent_buffer()

Call rcu_read_lock() before exiting the loop in
try_release_subpage_extent_buffer() because there is a rcu_read_unlock()
call past the loop.

This has been detected by the Clang thread-safety analyzer.

The Linux kernel CVE team has assigned CVE-2026-43358 to this issue.


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

	Issue introduced in 6.17 with commit ad580dfa388fabb52af033e3f8cc5d04be985e54 and fixed in 6.18.19 with commit 5e1ab71f74a1e61f1254dff128a764fdebaec0b8
	Issue introduced in 6.17 with commit ad580dfa388fabb52af033e3f8cc5d04be985e54 and fixed in 6.19.9 with commit 35b0c8768e848e1b7e32052db36b5fa59b6a33a1
	Issue introduced in 6.17 with commit ad580dfa388fabb52af033e3f8cc5d04be985e54 and fixed in 7.0 with commit b2840e33127ce0eea880504b7f133e780f567a9b
	Issue introduced in 6.16.4 with commit 10ec363cfefeeb77fda4c1ac20a531f21de45264

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-2026-43358
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/extent_io.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/5e1ab71f74a1e61f1254dff128a764fdebaec0b8
	https://git.kernel.org/stable/c/35b0c8768e848e1b7e32052db36b5fa59b6a33a1
	https://git.kernel.org/stable/c/b2840e33127ce0eea880504b7f133e780f567a9b