4.16-stable review patch. If anyone has any objections, please let me know.
------------------ From: Laura Abbott <[email protected]> commit c3bca5d450b620dd3d36e14b5e1f43639fd47d6b upstream. Commit a9445e47d897 ("posix-cpu-timers: Make set_process_cpu_timer() more robust") moved the check into the 'if' statement. Unfortunately, it did so on the right side of an && which means that it may get short circuited and never evaluated. This is easily reproduced with: $ cat loop.c void main() { struct rlimit res; /* set the CPU time limit */ getrlimit(RLIMIT_CPU,&res); res.rlim_cur = 2; res.rlim_max = 2; setrlimit(RLIMIT_CPU,&res); while (1); } Which will hang forever instead of being killed. Fix this by pulling the evaluation out of the if statement but checking the return value instead. Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1568337 Fixes: a9445e47d897 ("posix-cpu-timers: Make set_process_cpu_timer() more robust") Signed-off-by: Laura Abbott <[email protected]> Signed-off-by: Thomas Gleixner <[email protected]> Cc: [email protected] Cc: "Max R . P . Grossmann" <[email protected]> Cc: John Stultz <[email protected]> Link: https://lkml.kernel.org/r/[email protected] Signed-off-by: Greg Kroah-Hartman <[email protected]> --- kernel/time/posix-cpu-timers.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) --- a/kernel/time/posix-cpu-timers.c +++ b/kernel/time/posix-cpu-timers.c @@ -1205,10 +1205,12 @@ void set_process_cpu_timer(struct task_s u64 *newval, u64 *oldval) { u64 now; + int ret; WARN_ON_ONCE(clock_idx == CPUCLOCK_SCHED); + ret = cpu_timer_sample_group(clock_idx, tsk, &now); - if (oldval && cpu_timer_sample_group(clock_idx, tsk, &now) != -EINVAL) { + if (oldval && ret != -EINVAL) { /* * We are setting itimer. The *oldval is absolute and we update * it to be relative, *newval argument is relative and we update
