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Many devices implement highly accurate clocks, which the kernel manages as PTP Hardware Clocks (PHCs). Userspace applications rely on these clocks to timestamp events, trace workload execution, correlate timescales across devices, and keep various clocks in sync. The kernel’s current implementation of PTP clocks does not enforce file permissions checks for most device operations except for POSIX clock operations, where file mode is verified in the POSIX layer before forwarding the call to the PTP subsystem. Consequently, it is common practice to not give unprivileged userspace applications any access to PTP clocks whatsoever by giving the PTP chardevs 600 permissions. An example of users running into this limitation is documented in [1]. Additionally, POSIX layer requires WRITE permission even for readonly adjtime() calls which are used in PTP layer to return current frequency offset applied to the PHC. Add permission checks for functions that modify the state of a PTP device. Continue enforcing permission checks for POSIX clock operations (settime, adjtime) in the POSIX layer. Only require WRITE access for dynamic clocks adjtime() if any flags are set in the modes field. [1] https://lists.nwtime.org/sympa/arc/linuxptp-users/2024-01/msg00036.html Changes in v4: - Require FMODE_WRITE in ajtime() only for calls modifying the clock in any way. Acked-by: Richard Cochran <richardcochran@gmail.com> Reviewed-by: Vadim Fedorenko <vadim.fedorenko@linux.dev> Signed-off-by: Wojtek Wasko <wwasko@nvidia.com> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: David S. Miller <davem@davemloft.net> |
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| .. | ||
| alarmtimer.c | ||
| clockevents.c | ||
| clocksource-wdtest.c | ||
| clocksource.c | ||
| hrtimer.c | ||
| itimer.c | ||
| jiffies.c | ||
| Kconfig | ||
| Makefile | ||
| namespace.c | ||
| ntp.c | ||
| ntp_internal.h | ||
| posix-clock.c | ||
| posix-cpu-timers.c | ||
| posix-stubs.c | ||
| posix-timers.c | ||
| posix-timers.h | ||
| sched_clock.c | ||
| sleep_timeout.c | ||
| test_udelay.c | ||
| tick-broadcast-hrtimer.c | ||
| tick-broadcast.c | ||
| tick-common.c | ||
| tick-internal.h | ||
| tick-legacy.c | ||
| tick-oneshot.c | ||
| tick-sched.c | ||
| tick-sched.h | ||
| time.c | ||
| time_test.c | ||
| timeconst.bc | ||
| timeconv.c | ||
| timecounter.c | ||
| timekeeping.c | ||
| timekeeping.h | ||
| timekeeping_debug.c | ||
| timekeeping_internal.h | ||
| timer.c | ||
| timer_list.c | ||
| timer_migration.c | ||
| timer_migration.h | ||
| vsyscall.c | ||