CVE-2026-64266: fuse: re-lock request before returning from fuse_ref_folio()

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

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

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

fuse: re-lock request before returning from fuse_ref_folio()

fuse_ref_folio() unlocks the request but does not re-lock it before
returning. fuse_chan_abort() can end the request and the async end
callback (eg fuse_writepage_free()) can free the args while the
subsequent copy chain logic after fuse_ref_folio() accesses them,
leading to use-after-free issues.

Fix this by locking the request in fuse_ref_folio() before returning.

The Linux kernel CVE team has assigned CVE-2026-64266 to this issue.


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

	Issue introduced in 2.6.35 with commit c3021629a0d820247ee12b6c5192a1d5380e21c6 and fixed in 5.10.261 with commit 1f9156714592356b4fda57beac7eab9c2a462dd3
	Issue introduced in 2.6.35 with commit c3021629a0d820247ee12b6c5192a1d5380e21c6 and fixed in 5.15.212 with commit 5630da218a45ba80f0aba0846cbe8aa655da122b
	Issue introduced in 2.6.35 with commit c3021629a0d820247ee12b6c5192a1d5380e21c6 and fixed in 6.1.178 with commit 1ca605cfa59377f0143fb35b5b01360f37d1b7c4
	Issue introduced in 2.6.35 with commit c3021629a0d820247ee12b6c5192a1d5380e21c6 and fixed in 6.6.145 with commit 0e4a5a000123d81234e27a2f8187688cf608f755
	Issue introduced in 2.6.35 with commit c3021629a0d820247ee12b6c5192a1d5380e21c6 and fixed in 6.12.96 with commit e6aa539720c3d8def69683ed0c07cf9faea4e8be
	Issue introduced in 2.6.35 with commit c3021629a0d820247ee12b6c5192a1d5380e21c6 and fixed in 6.18.39 with commit be353caffa8640f5e25fb3714ce8b0cef5e410e5
	Issue introduced in 2.6.35 with commit c3021629a0d820247ee12b6c5192a1d5380e21c6 and fixed in 7.1.4 with commit 65a1c2551f7e16085acbb54aedde1feaa559ba7a
	Issue introduced in 2.6.35 with commit c3021629a0d820247ee12b6c5192a1d5380e21c6 and fixed in 7.2-rc1 with commit b5befa80fdbe287a98480effed9564712924add5

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-2026-64266
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/fuse/dev.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/1f9156714592356b4fda57beac7eab9c2a462dd3
	https://git.kernel.org/stable/c/5630da218a45ba80f0aba0846cbe8aa655da122b
	https://git.kernel.org/stable/c/1ca605cfa59377f0143fb35b5b01360f37d1b7c4
	https://git.kernel.org/stable/c/0e4a5a000123d81234e27a2f8187688cf608f755
	https://git.kernel.org/stable/c/e6aa539720c3d8def69683ed0c07cf9faea4e8be
	https://git.kernel.org/stable/c/be353caffa8640f5e25fb3714ce8b0cef5e410e5
	https://git.kernel.org/stable/c/65a1c2551f7e16085acbb54aedde1feaa559ba7a
	https://git.kernel.org/stable/c/b5befa80fdbe287a98480effed9564712924add5