[patch 057/100] posix-timers: fix RLIMIT_CPU && fork()

[Chris Wright]

-stable review patch.  If anyone has any objections, please let us know.
---------------------

From: Oleg Nesterov <oleg@xxxxxxxxxx>

upstream commit: 6279a751fe096a21dc7704e918d570d3ff06e769

See http://bugzilla.kernel.org/show_bug.cgi?id=12911

copy_signal() copies signal->rlim, but RLIMIT_CPU is "lost". Because
posix_cpu_timers_init_group() sets cputime_expires.prof_exp = 0 and thus
fastpath_timer_check() returns false unless we have other expired cpu timers.

Change copy_signal() to set cputime_expires.prof_exp if we have RLIMIT_CPU.
Also, set cputimer.running = 1 in that case. This is not strictly necessary,
but imho makes sense.

Reported-by: Peter Lojkin <ia6432@xxxxxxxx>
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Acked-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Peter Lojkin <ia6432@xxxxxxxx>
Cc: Roland McGrath <roland@xxxxxxxxxx>
Cc: stable@xxxxxxxxxx
LKML-Reference: <20090327000607.GA10104@xxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
Signed-off-by: Chris Wright <chrisw@xxxxxxxxxxxx>
---
 kernel/fork.c |   13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -808,6 +808,12 @@ static void posix_cpu_timers_init_group(
 	sig->cputime_expires.virt_exp = cputime_zero;
 	sig->cputime_expires.sched_exp = 0;
 
+	if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
+		sig->cputime_expires.prof_exp =
+			secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
+		sig->cputimer.running = 1;
+	}
+
 	/* The timer lists. */
 	INIT_LIST_HEAD(&sig->cpu_timers[0]);
 	INIT_LIST_HEAD(&sig->cpu_timers[1]);
@@ -823,11 +829,8 @@ static int copy_signal(unsigned long clo
 		atomic_inc(&current->signal->live);
 		return 0;
 	}
-	sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);
-
-	if (sig)
-		posix_cpu_timers_init_group(sig);
 
+	sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);
 	tsk->signal = sig;
 	if (!sig)
 		return -ENOMEM;
@@ -865,6 +868,8 @@ static int copy_signal(unsigned long clo
 	memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
 	task_unlock(current->group_leader);
 
+	posix_cpu_timers_init_group(sig);
+
 	acct_init_pacct(&sig->pacct);
 
 	tty_audit_fork(sig);

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