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Subject[PATCH] time: POSIX CPU timers: Ensure that variable is initialized
Date
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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