posix-timers: Make signal overrun accounting sensible

The handling of the timer overrun in the signal code is inconsistent as it
takes previous overruns into account. This is just wrong as after the
reprogramming of a timer the overrun count starts over from a clean state,
i.e. 0.

Don't touch info::si_overrun in send_sigqueue() and only store the overrun
value at signal delivery time, which is computed from the timer itself
relative to the expiry time.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/all/20241105064213.106738193@linutronix.de

diff --git a/kernel/signal.c b/kernel/signal.c
index 68e6bc70ccf2cfb5738e681e4b848d3c711a3276..ba7159b25d514fc5c961be790e2c6f875ded1c41 100644 (file)
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1968,15 +1968,9 @@ int send_sigqueue(struct sigqueue *q, struct pid *pid, enum pid_type type, int s
 
        ret = 0;
        if (unlikely(!list_empty(&q->list))) {
-               /*
-                * If an SI_TIMER entry is already queue just increment
-                * the overrun count.
-                */
-               q->info.si_overrun++;
                result = TRACE_SIGNAL_ALREADY_PENDING;
                goto out;
        }
-       q->info.si_overrun = 0;
 
        signalfd_notify(t, sig);
        pending = (type != PIDTYPE_PID) ? &t->signal->shared_pending : &t->pending;

diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c
index b380e25d49474d674a93ba4896d7bd32021bd267..66ed49efc02f44c3ddddf7baf7f77d024d5ecb82 100644 (file)
--- a/kernel/time/posix-timers.c
+++ b/kernel/time/posix-timers.c
@@ -233,11 +233,12 @@ __initcall(init_posix_timers);
  * The siginfo si_overrun field and the return value of timer_getoverrun(2)
  * are of type int. Clamp the overrun value to INT_MAX
  */
-static inline int timer_overrun_to_int(struct k_itimer *timr, int baseval)
+static inline int timer_overrun_to_int(struct k_itimer *timr)
 {
-       s64 sum = timr->it_overrun_last + (s64)baseval;
+       if (timr->it_overrun_last > (s64)INT_MAX)
+               return INT_MAX;
 
-       return sum > (s64)INT_MAX ? INT_MAX : (int)sum;
+       return (int)timr->it_overrun_last;
 }
 
 static void common_hrtimer_rearm(struct k_itimer *timr)
@@ -280,7 +281,7 @@ bool posixtimer_deliver_signal(struct kernel_siginfo *info)
                timr->it_overrun = -1LL;
                ++timr->it_signal_seq;
 
-               info->si_overrun = timer_overrun_to_int(timr, info->si_overrun);
+               info->si_overrun = timer_overrun_to_int(timr);
        }
        ret = true;
 
@@ -774,7 +775,7 @@ SYSCALL_DEFINE1(timer_getoverrun, timer_t, timer_id)
        if (!timr)
                return -EINVAL;
 
-       overrun = timer_overrun_to_int(timr, 0);
+       overrun = timer_overrun_to_int(timr);
        unlock_timer(timr, flags);
 
        return overrun;