linux-cve-announce - CVE-2025-71102: scs: fix a wrong parameter in __scs

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Message-ID: <2026011407-CVE-2025-71102-f4be@gregkh>
Date: Wed, 14 Jan 2026 16:06:07 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-71102: scs: fix a wrong parameter in __scs_magic

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

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

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

scs: fix a wrong parameter in __scs_magic

__scs_magic() needs a 'void *' variable, but a 'struct task_struct *' is
given.  'task_scs(tsk)' is the starting address of the task's shadow call
stack, and '__scs_magic(task_scs(tsk))' is the end address of the task's
shadow call stack.  Here should be '__scs_magic(task_scs(tsk))'.

The user-visible effect of this bug is that when CONFIG_DEBUG_STACK_USAGE
is enabled, the shadow call stack usage checking function
(scs_check_usage) would scan an incorrect memory range.  This could lead

1. **Inaccurate stack usage reporting**: The function would calculate
   wrong usage statistics for the shadow call stack, potentially showing
   incorrect value in kmsg.

2. **Potential kernel crash**: If the value of __scs_magic(tsk)is
   greater than that of __scs_magic(task_scs(tsk)), the for loop may
   access unmapped memory, potentially causing a kernel panic.  However,
   this scenario is unlikely because task_struct is allocated via the slab
   allocator (which typically returns lower addresses), while the shadow
   call stack returned by task_scs(tsk) is allocated via vmalloc(which
   typically returns higher addresses).

However, since this is purely a debugging feature
(CONFIG_DEBUG_STACK_USAGE), normal production systems should be not
unaffected.  The bug only impacts developers and testers who are actively
debugging stack usage with this configuration enabled.

The Linux kernel CVE team has assigned CVE-2025-71102 to this issue.

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

	Issue introduced in 5.8 with commit 5bbaf9d1fcb9be696ee9a61636ab6803556c70f2 and fixed in 6.1.160 with commit 57ba40b001be27786d0570dd292289df748b306b
	Issue introduced in 5.8 with commit 5bbaf9d1fcb9be696ee9a61636ab6803556c70f2 and fixed in 6.6.120 with commit 062774439d442882b44f5eab8c256ad3423ef284
	Issue introduced in 5.8 with commit 5bbaf9d1fcb9be696ee9a61636ab6803556c70f2 and fixed in 6.12.64 with commit 9ef28943471a16e4f9646bc3e8e2de148e7d8d7b
	Issue introduced in 5.8 with commit 5bbaf9d1fcb9be696ee9a61636ab6803556c70f2 and fixed in 6.18.3 with commit a19fb3611e4c06624fc0f83ef19f4fb8d57d4751
	Issue introduced in 5.8 with commit 5bbaf9d1fcb9be696ee9a61636ab6803556c70f2 and fixed in 6.19-rc1 with commit 08bd4c46d5e63b78e77f2605283874bbe868ab19

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-2025-71102
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:
	kernel/scs.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/57ba40b001be27786d0570dd292289df748b306b
	https://git.kernel.org/stable/c/062774439d442882b44f5eab8c256ad3423ef284
	https://git.kernel.org/stable/c/9ef28943471a16e4f9646bc3e8e2de148e7d8d7b
	https://git.kernel.org/stable/c/a19fb3611e4c06624fc0f83ef19f4fb8d57d4751
	https://git.kernel.org/stable/c/08bd4c46d5e63b78e77f2605283874bbe868ab19