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Commit 191ce9d1 authored by Martin Schwidefsky's avatar Martin Schwidefsky
Browse files

s390/time: fix clocksource steering for negative clock offsets 



The TOD clock offset injected by an STP sync check can be negative.
If the resulting total tod_steering_delta gets negative the kernel
will panic.

Change the type of tod_steering_delta to a signed type.

Reported-by: default avatarDan Carpenter <dan.carpenter@oracle.com>
Fixes: 75c7b6f3 ("s390/time: steer clocksource on STP sync events")
Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent 68962269

arch/s390/kernel/time.c

+3 −4
Original line number Diff line number Diff line
@@ -63,7 +63,7 @@ unsigned char ptff_function_mask[16]; 
static unsigned long long lpar_offset;

static unsigned long long initial_leap_seconds;

static unsigned long long tod_steering_end;

static unsigned long long tod_steering_delta;

static long long tod_steering_delta;



/*

 * Get time offsets with PTFF
@@ -223,8 +223,7 @@ static cycle_t read_tod_clock(struct clocksource *cs) 
		 * therefore steered in ~9h. The adjust will decrease

		 * over time, until it finally reaches 0.

		 */

		now += ((s64) tod_steering_delta < 0) ?

			(adj >> 15) : -(adj >> 15);

		now += (tod_steering_delta < 0) ? (adj >> 15) : -(adj >> 15);

	preempt_enable();

	return now;

}
@@ -412,7 +411,7 @@ static void clock_sync_global(unsigned long long delta) 
	adj = tod_steering_end - now;

	if (unlikely((s64) adj >= 0))

		/* Calculate how much of the old adjustment is left. */

		tod_steering_delta = ((s64) tod_steering_delta < 0) ?

		tod_steering_delta = (tod_steering_delta < 0) ?

			-(adj >> 15) : (adj >> 15);

	tod_steering_delta += delta;

	if ((abs(tod_steering_delta) >> 48) != 0)