Messages in this thread Patch in this message | | | From | "Max R. P. Grossmann" <> | Subject | [PATCH] time: POSIX CPU timers: Ensure that variable is initialized | Date | Mon, 8 Jan 2018 20:01:57 +0100 |
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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 <m@max.pm> --- 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
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