CVE-2026-64265: fuse: clear intr_entry in fuse_resend and fuse_remove_pending_req

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

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

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

fuse: clear intr_entry in fuse_resend and fuse_remove_pending_req

When fuse_resend() moves a request from fpq->processing back to
fiq->pending, it sets FR_PENDING and clears FR_SENT but does not
remove the requests intr_entry from fiq->interrupts.  If the
request had FR_INTERRUPTED set from a prior signal, intr_entry
remains dangling on fiq->interrupts.  When the requesting task
then receives a fatal signal, fuse_remove_pending_req() sees
FR_PENDING=1, removes the request from fiq->pending and frees it
via the refcount path, also without cleaning intr_entry.  The
stale intr_entry causes use-after-free when fuse_read_interrupt()
iterates fiq->interrupts:
  - list_del_init(&req->intr_entry) -> UAF write on freed slab
  - req->in.h.unique -> UAF read, data leaked to userspace

Remove intr_entry from fiq->interrupts in fuse_resend() for
interrupted requests before they are placed back on fiq->pending.

Add a WARN_ON if the intr_entry is not empty on request destruction.

The Linux kernel CVE team has assigned CVE-2026-64265 to this issue.


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

	Issue introduced in 6.9 with commit 760eac73f9f69aa28fcb3050b4946c2dcc656d12 and fixed in 6.12.96 with commit 1d8ecd0cd696a5df0b2f72046a4ccee5d2a8ec2c
	Issue introduced in 6.9 with commit 760eac73f9f69aa28fcb3050b4946c2dcc656d12 and fixed in 6.18.39 with commit 7366e6f4d2b4c7002b13fb01219e83679dad4127
	Issue introduced in 6.9 with commit 760eac73f9f69aa28fcb3050b4946c2dcc656d12 and fixed in 7.1.4 with commit 893479015cb6442fd389d3b553ab3036c9541715
	Issue introduced in 6.9 with commit 760eac73f9f69aa28fcb3050b4946c2dcc656d12 and fixed in 7.2-rc1 with commit f8fce75fedf73ac72aa09163deb8f4291fdcaad2

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-2026-64265
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/1d8ecd0cd696a5df0b2f72046a4ccee5d2a8ec2c
	https://git.kernel.org/stable/c/7366e6f4d2b4c7002b13fb01219e83679dad4127
	https://git.kernel.org/stable/c/893479015cb6442fd389d3b553ab3036c9541715
	https://git.kernel.org/stable/c/f8fce75fedf73ac72aa09163deb8f4291fdcaad2