linux-cve-announce - CVE-2025-38534: netfs: Fix copy-to-cache so that it performs collection with ceph+fscache

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Message-ID: <2025081656-CVE-2025-38534-5573@gregkh>
Date: Sat, 16 Aug 2025 13:14:05 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-38534: netfs: Fix copy-to-cache so that it performs collection with ceph+fscache

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

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

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

netfs: Fix copy-to-cache so that it performs collection with ceph+fscache

The netfs copy-to-cache that is used by Ceph with local caching sets up a
new request to write data just read to the cache.  The request is started
and then left to look after itself whilst the app continues.  The request
gets notified by the backing fs upon completion of the async DIO write, but
then tries to wake up the app because NETFS_RREQ_OFFLOAD_COLLECTION isn't
set - but the app isn't waiting there, and so the request just hangs.

Fix this by setting NETFS_RREQ_OFFLOAD_COLLECTION which causes the
notification from the backing filesystem to put the collection onto a work
queue instead.

The Linux kernel CVE team has assigned CVE-2025-38534 to this issue.

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

	Issue introduced in 6.14 with commit e2d46f2ec332533816417b60933954173f602121 and fixed in 6.15.8 with commit 1ebe58cef84eab22b41b4d5e72c2051ebf00af50
	Issue introduced in 6.14 with commit e2d46f2ec332533816417b60933954173f602121 and fixed in 6.16 with commit 4c238e30774e3022a505fa54311273add7570f13

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-2025-38534
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/netfs/read_pgpriv2.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/1ebe58cef84eab22b41b4d5e72c2051ebf00af50
	https://git.kernel.org/stable/c/4c238e30774e3022a505fa54311273add7570f13