If cpu_timer_sample_group returns -EINVAL, it will not have written into *sample. Checking for cpu_timer_sample_group's return value precludes the potential use of an uninitialized value of now in the following block. Given an invalid clock_idx, the previous code could otherwise overwrite *oldval in an undefined manner. This is now prevented. We also exploit short-circuiting of && to sample the timer only if the result will actually be used to update *oldval.
Signed-off-by: Max R. P. Grossmann <[email protected]> --- kernel/time/posix-cpu-timers.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c index 1f27887aa194..e54638be6e19 100644 --- a/kernel/time/posix-cpu-timers.c +++ b/kernel/time/posix-cpu-timers.c @@ -1189,9 +1189,8 @@ void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx, u64 now; WARN_ON_ONCE(clock_idx == CPUCLOCK_SCHED); - cpu_timer_sample_group(clock_idx, tsk, &now); - if (oldval) { + if (oldval && cpu_timer_sample_group(clock_idx, tsk, &now) != -EINVAL) { /* * We are setting itimer. The *oldval is absolute and we update * it to be relative, *newval argument is relative and we update -- 2.15.1
