From: Maoyi Xie Date: Thu, 28 May 2026 06:33:11 +0000 (+0800) Subject: ntsync: Honour caller's time namespace for absolute MONOTONIC timeouts X-Git-Url: http://git.ipfire.org/gitweb/?a=commitdiff_plain;h=180a232ea78003d1dc869b217b4e49106fd58e8f;p=thirdparty%2Fkernel%2Flinux.git ntsync: Honour caller's time namespace for absolute MONOTONIC timeouts ntsync_schedule() takes the absolute timeout from userspace and hands it to schedule_hrtimeout_range_clock() with HRTIMER_MODE_ABS. For the default CLOCK_MONOTONIC path, it does not call timens_ktime_to_host() first. A process inside a CLOCK_MONOTONIC time namespace computes the absolute timeout in its own clock view. The kernel reads the same value against the host clock. The two differ by the namespace offset. The timeout then fires too early or too late. Other users of absolute timeouts run the ktime through timens_ktime_to_host() before starting the hrtimer. ntsync was added later and missed that step. /dev/ntsync is mode 0666. Any user inside a time namespace that can open it is affected. The visible effect is wrong timeout behaviour for Wine in a container that sets a CLOCK_MONOTONIC offset. Reproducer: unshare --user --time, set the monotonic offset to -10s, issue NTSYNC_IOC_WAIT_ANY with a 100 ms absolute MONOTONIC timeout. The baseline run elapses about 100 ms. The run inside the namespace elapses about 0 ms. Apply timens_ktime_to_host() to the parsed timeout when the caller did not set NTSYNC_WAIT_REALTIME. The helper does nothing in the initial time namespace, so the fast path is unchanged. Fixes: b4a7b5fe3f51 ("ntsync: Introduce NTSYNC_IOC_WAIT_ANY.") Signed-off-by: Maoyi Xie Signed-off-by: Thomas Gleixner Reviewed-by: Elizabeth Figura Link: https://patch.msgid.link/20260528063311.3300393-3-maoyixie.tju@gmail.com --- diff --git a/drivers/misc/ntsync.c b/drivers/misc/ntsync.c index 30af282262efb..02c9d1192812a 100644 --- a/drivers/misc/ntsync.c +++ b/drivers/misc/ntsync.c @@ -19,6 +19,7 @@ #include #include #include +#include #include #define NTSYNC_NAME "ntsync" @@ -836,6 +837,8 @@ static int ntsync_schedule(const struct ntsync_q *q, const struct ntsync_wait_ar if (args->flags & NTSYNC_WAIT_REALTIME) clock = CLOCK_REALTIME; + else + timeout = timens_ktime_to_host(clock, timeout); do { if (signal_pending(current)) {