FAILED: patch "[PATCH] timekeeping: Require permission to set auxiliary clocks" failed to apply to 6.18-stable tree

FAILED: patch "[PATCH] timekeeping: Require permission to set auxiliary clocks" failed to apply to 6.18-stable tree

[Sasha Levin]

The patch below does not apply to the 6.18-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.18.y
git checkout FETCH_HEAD
git cherry-pick -x 524d95c8a2000cba6cb80a173d76cb746c561244
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '20261107051357-failed-6.18-524d95c8a200@kernel.org' --subject-prefix 'PATCH 6.18.y' 'HEAD^..'

Thanks,
Sasha

------------------ original commit in Linus's tree ------------------

From 524d95c8a2000cba6cb80a173d76cb746c561244 Mon Sep 17 00:00:00 2001
From: Daehyeon Ko <4ncienth@gmail.com>
Date: Mon, 19 Oct 2026 17:03:24 +0900
Subject: [PATCH] timekeeping: Require permission to set auxiliary clocks

The generic clock_settime() entry point delegates permission checks to
each clock-specific callback. aux_clock_set() does not perform one. Once
an administrator enables an auxiliary clock, any local process can
therefore change the global clock offset.

A test process running as UID and GID 65534 with no effective, permitted,
inheritable, or ambient capabilities set CLOCK_AUX0 successfully, and a
separate process observed the new value. The same process was denied by
clock_adjtime(). An AppArmor profile denying sys_time also blocked
CLOCK_REALTIME changes but did not see the auxiliary clock operation.

Call security_settime64() before mutating the auxiliary timekeeper. This
matches CLOCK_REALTIME's permission model, enforces initial-user-namespace
CAP_SYS_TIME, and gives LSMs the settime hook while preserving authorized
clock changes.

Fixes: 60ecc26ec5af ("timekeeping: Provide time setter for auxiliary clocks")
Signed-off-by: Daehyeon Ko <4ncienth@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Tested-by: shaos <shawnq1@163.com>
Acked-by: John Stultz <jstultz@google.com>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20261019080324.4147815-1-4ncienth@gmail.com
---
 kernel/time/timekeeping.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index ea2e6e55f37bf..1b342825bd8f1 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -14,6 +14,7 @@
 #include <linux/random.h>
 #include <linux/sched/clock.h>
 #include <linux/sched/loadavg.h>
+#include <linux/security.h>
 #include <linux/static_key.h>
 #include <linux/stop_machine.h>
 #include <linux/syscore_ops.h>
@@ -3215,11 +3216,15 @@ static int aux_clock_set(const clockid_t id, const struct timespec64 *tnew)
 	struct tk_data *aux_tkd = aux_get_tk_data(id);
 	struct timekeeper *aux_tks;
 	ktime_t tnow, nsecs;
+	int ret;
 
 	if (!timespec64_valid_settod(tnew))
 		return -EINVAL;
 	if (!aux_tkd)
 		return -ENODEV;
+	ret = security_settime64(tnew, NULL);
+	if (ret)
+		return ret;
 
 	aux_tks = &aux_tkd->shadow_timekeeper;
 
-- 
2.53.0

[PATCH 6.18.y] timekeeping: Require permission to set auxiliary clocks

[Thomas Gleixner]

From: Daehyeon Ko <4ncienth@gmail.com>

commit 524d95c8a2000cba6cb80a173d76cb746c561244 upstream.

The generic clock_settime() entry point delegates permission checks to
each clock-specific callback. aux_clock_set() does not perform one. Once
an administrator enables an auxiliary clock, any local process can
therefore change the global clock offset.

A test process running as UID and GID 65534 with no effective, permitted,
inheritable, or ambient capabilities set CLOCK_AUX0 successfully, and a
separate process observed the new value. The same process was denied by
clock_adjtime(). An AppArmor profile denying sys_time also blocked
CLOCK_REALTIME changes but did not see the auxiliary clock operation.

Call security_settime64() before mutating the auxiliary timekeeper. This
matches CLOCK_REALTIME's permission model, enforces initial-user-namespace
CAP_SYS_TIME, and gives LSMs the settime hook while preserving authorized
clock changes.

Fixes: 60ecc26ec5af ("timekeeping: Provide time setter for auxiliary clocks")
Signed-off-by: Daehyeon Ko <4ncienth@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Tested-by: shaos <shawnq1@163.com>
Acked-by: John Stultz <jstultz@google.com>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20261019080324.4147815-1-4ncienth@gmail.com
---
 kernel/time/timekeeping.c |    5 +++++
 1 file changed, 5 insertions(+)
---
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -14,6 +14,7 @@
 #include <linux/sched.h>
 #include <linux/sched/loadavg.h>
 #include <linux/sched/clock.h>
+#include <linux/security.h>
 #include <linux/syscore_ops.h>
 #include <linux/clocksource.h>
 #include <linux/jiffies.h>
@@ -2936,11 +2937,15 @@ static int aux_clock_set(const clockid_t
 	struct tk_data *aux_tkd = aux_get_tk_data(id);
 	struct timekeeper *aux_tks;
 	ktime_t tnow, nsecs;
+	int ret;
 
 	if (!timespec64_valid_settod(tnew))
 		return -EINVAL;
 	if (!aux_tkd)
 		return -ENODEV;
+	ret = security_settime64(tnew, NULL);
+	if (ret)
+		return ret;
 
 	aux_tks = &aux_tkd->shadow_timekeeper;
 

Re: [PATCH 6.18.y] timekeeping: Require permission to set auxiliary clocks

[Sasha Levin]

> timekeeping: Require permission to set auxiliary clocks

Queued for 6.18, thanks.

-- 
Thanks,
Sasha