CVE-2026-80857: fuse: wait for FR_FINISHED on abort_on_kill to prevent use-after-free

CVE-2026-80857: fuse: wait for FR_FINISHED on abort_on_kill to prevent use-after-free

[Greg Kroah-Hartman]

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

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

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

fuse: wait for FR_FINISHED on abort_on_kill to prevent use-after-free

The abort_on_kill path in request_wait_answer() calls fuse_abort_conn()
and returns without waiting for FR_FINISHED.  If fuse_dev_do_write() is
concurrently processing the same request (FR_LOCKED set), the caller
frees req->args while it is still being accessed, causing a
use-after-free.

Fix this by jumping to the existing wait_event(FR_FINISHED) instead of
returning early.  The wait will not hang because fuse_abort_conn()
ensures all requests are ended.

The Linux kernel CVE team has assigned CVE-2026-80857 to this issue.


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

	Issue introduced in 7.1 with commit 204aa22a686bfee48daca7db620c1e017615f2ff and fixed in 7.2.3 with commit 715cb86e33cda43f5224cdc3fd5610c0b6a46f7a
	Issue introduced in 7.1 with commit 204aa22a686bfee48daca7db620c1e017615f2ff and fixed in 7.3-rc1 with commit 64b0b5cacbd2fea88001464cb712c9dfc795b26e
	Issue introduced in 6.18.25 with commit 0c7fca880a40a209a9c92be14143996d14b93ff6
	Issue introduced in 7.0.2 with commit 300e812b882a174dca675d8028684001ad5826bc

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-2026-80857
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/715cb86e33cda43f5224cdc3fd5610c0b6a46f7a
	https://git.kernel.org/stable/c/64b0b5cacbd2fea88001464cb712c9dfc795b26e