github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-11-06 21:58:01 +01:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

timekeeping: Require permission to set auxiliary clocks

Browse Source 
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: 60ecc26ec5 ("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
This commit is contained in:
Daehyeon Ko 2026-10-19 17:03:24 +09:00 committed by Thomas Gleixner
parent 8ccd731b63
commit 524d95c8a2
1 changed files with 5 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
kernel/time/timekeeping.c
View File

@ -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;