linux-cve-announce - CVE-2025-39715: parisc: Revise gateway LWS calls to probe user read access

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Message-ID: <2025090551-CVE-2025-39715-6248@gregkh>
Date: Fri,  5 Sep 2025 19:21:28 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-39715: parisc: Revise gateway LWS calls to probe user read access

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

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

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

parisc: Revise gateway LWS calls to probe user read access

We use load and stbys,e instructions to trigger memory reference
interruptions without writing to memory. Because of the way read
access support is implemented, read access interruptions are only
triggered at privilege levels 2 and 3. The kernel and gateway
page execute at privilege level 0, so this code never triggers
a read access interruption. Thus, it is currently possible for
user code to execute a LWS compare and swap operation at an
address that is read protected at privilege level 3 (PRIV_USER).

Fix this by probing read access rights at privilege level 3 and
branching to lws_fault if access isn't allowed.

The Linux kernel CVE team has assigned CVE-2025-39715 to this issue.


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

	Fixed in 6.1.149 with commit e8b496c52aa0c6572d88db7cab85aeea6f9c194d
	Fixed in 6.6.103 with commit 8bccf47adbf658293528e86960e6d6f736b1c9f7
	Fixed in 6.12.44 with commit bc0a24c24ceebabb5ba65900e332233d79e625e6
	Fixed in 6.16.4 with commit 9b6af875baba9c4679b55f4561e201485451305f
	Fixed in 6.17-rc1 with commit f6334f4ae9a4e962ba74b026e1d965dfdf8cbef8

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-2025-39715
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:
	arch/parisc/kernel/syscall.S


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/e8b496c52aa0c6572d88db7cab85aeea6f9c194d
	https://git.kernel.org/stable/c/8bccf47adbf658293528e86960e6d6f736b1c9f7
	https://git.kernel.org/stable/c/bc0a24c24ceebabb5ba65900e332233d79e625e6
	https://git.kernel.org/stable/c/9b6af875baba9c4679b55f4561e201485451305f
	https://git.kernel.org/stable/c/f6334f4ae9a4e962ba74b026e1d965dfdf8cbef8