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P . Grossmann" , John Stultz Subject: [PATCH 4.16 07/26] posix-cpu-timers: Ensure set_process_cpu_timer is always evaluated Date: Wed, 25 Apr 2018 12:33:16 +0200 Message-Id: <20180425103315.145805470@linuxfoundation.org> X-Mailer: git-send-email 2.17.0 In-Reply-To: <20180425103314.842517924@linuxfoundation.org> References: <20180425103314.842517924@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 4.16-stable review patch. If anyone has any objections, please let me know. ------------------ From: Laura Abbott 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 Signed-off-by: Thomas Gleixner Cc: stable@vger.kernel.org Cc: "Max R . P . Grossmann" Cc: John Stultz Link: https://lkml.kernel.org/r/20180417215742.2521-1-labbott@redhat.com Signed-off-by: Greg Kroah-Hartman --- 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