[PATCH] posix-cpu-timers: Fix spuriously armed 0-value itimer

[Frederic Weisbecker]

Resetting/stopping an itimer eventually leads to it being reprogrammed
with an actual "0" value. As a result the itimer expires on the next
tick, triggering an unexpected signal.

To fix this, make sure that
struct signal_struct::it[CPUCLOCK_PROF/VIRT]::expires is set to 0 when
setitimer() passes a 0 it_value, indicating that the timer must stop.

Reported-by: Victor Stinner <vstinner@xxxxxxxxxx>
Fixes: 406dd42bd1ba ("posix-cpu-timers: Force next expiration recalc after itimer reset")
Signed-off-by: Frederic Weisbecker <frederic@xxxxxxxxxx>
Cc: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
 kernel/time/posix-cpu-timers.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c
index ee736861b18f..643d412ac623 100644
--- a/kernel/time/posix-cpu-timers.c
+++ b/kernel/time/posix-cpu-timers.c
@@ -1404,7 +1404,8 @@ void set_process_cpu_timer(struct task_struct *tsk, unsigned int clkid,
 			}
 		}
 
-		*newval += now;
+		if (*newval)
+			*newval += now;
 	}
 
 	/*
-- 
2.25.1