Merge branch 'core-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'core-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  futex: Handle futex value corruption gracefully
  futex: Handle user space corruption gracefully
  futex_lock_pi() key refcnt fix
  softlockup: Add sched_clock_tick() to avoid kernel warning on kgdb resume

4 files changed, 49 insertions, 6 deletions

diff --git a/include/linux/sched.h b/include/linux/sched.h
index abdfacc58653..78efe7c485ac 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -310,6 +310,7 @@ extern void sched_show_task(struct task_struct *p);
 #ifdef CONFIG_DETECT_SOFTLOCKUP
 extern void softlockup_tick(void);
 extern void touch_softlockup_watchdog(void);
+extern void touch_softlockup_watchdog_sync(void);
 extern void touch_all_softlockup_watchdogs(void);
 extern int proc_dosoftlockup_thresh(struct ctl_table *table, int write,
                                     void __user *buffer,
@@ -323,6 +324,9 @@ static inline void softlockup_tick(void)
 static inline void touch_softlockup_watchdog(void)
 {
 }
+static inline void touch_softlockup_watchdog_sync(void)
+{
+}
 static inline void touch_all_softlockup_watchdogs(void)
 {
 }
diff --git a/kernel/futex.c b/kernel/futex.c
index d9b3a2228f9d..e7a35f1039e7 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -530,8 +530,25 @@ lookup_pi_state(u32 uval, struct futex_hash_bucket *hb,
                                 return -EINVAL;
 
                         WARN_ON(!atomic_read(&pi_state->refcount));
-                        WARN_ON(pid && pi_state->owner &&
-                                pi_state->owner->pid != pid);
+
+                        /*
+                         * When pi_state->owner is NULL then the owner died
+                         * and another waiter is on the fly. pi_state->owner
+                         * is fixed up by the task which acquires
+                         * pi_state->rt_mutex.
+                         *
+                         * We do not check for pid == 0 which can happen when
+                         * the owner died and robust_list_exit() cleared the
+                         * TID.
+                         */
+                        if (pid && pi_state->owner) {
+                                /*
+                                 * Bail out if user space manipulated the
+                                 * futex value.
+                                 */
+                                if (pid != task_pid_vnr(pi_state->owner))
+                                        return -EINVAL;
+                        }
 
                         atomic_inc(&pi_state->refcount);
                         *ps = pi_state;
@@ -758,6 +775,13 @@ static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this)
         if (!pi_state)
                 return -EINVAL;
 
+        /*
+         * If current does not own the pi_state then the futex is
+         * inconsistent and user space fiddled with the futex value.
+         */
+        if (pi_state->owner != current)
+                return -EINVAL;
+
         raw_spin_lock(&pi_state->pi_mutex.wait_lock);
         new_owner = rt_mutex_next_owner(&pi_state->pi_mutex);
 
@@ -1971,7 +1995,7 @@ retry_private:
         /* Unqueue and drop the lock */
         unqueue_me_pi(&q);
 
-        goto out;
+        goto out_put_key;
 
 out_unlock_put_key:
         queue_unlock(&q, hb);
diff --git a/kernel/kgdb.c b/kernel/kgdb.c
index c7ade62e4ef0..761fdd2b3034 100644
--- a/kernel/kgdb.c
+++ b/kernel/kgdb.c
@@ -599,7 +599,7 @@ static void kgdb_wait(struct pt_regs *regs)
 
         /* Signal the primary CPU that we are done: */
         atomic_set(&cpu_in_kgdb[cpu], 0);
-        touch_softlockup_watchdog();
+        touch_softlockup_watchdog_sync();
         clocksource_touch_watchdog();
         local_irq_restore(flags);
 }
@@ -1453,7 +1453,7 @@ acquirelock:
             (kgdb_info[cpu].task &&
              kgdb_info[cpu].task->pid != kgdb_sstep_pid) && --sstep_tries) {
                 atomic_set(&kgdb_active, -1);
-                touch_softlockup_watchdog();
+                touch_softlockup_watchdog_sync();
                 clocksource_touch_watchdog();
                 local_irq_restore(flags);
 
@@ -1553,7 +1553,7 @@ kgdb_restore:
         }
         /* Free kgdb_active */
         atomic_set(&kgdb_active, -1);
-        touch_softlockup_watchdog();
+        touch_softlockup_watchdog_sync();
         clocksource_touch_watchdog();
         local_irq_restore(flags);
 
diff --git a/kernel/softlockup.c b/kernel/softlockup.c
index d22579087e27..0d4c7898ab80 100644
--- a/kernel/softlockup.c
+++ b/kernel/softlockup.c
@@ -25,6 +25,7 @@ static DEFINE_SPINLOCK(print_lock);
 static DEFINE_PER_CPU(unsigned long, softlockup_touch_ts); /* touch timestamp */
 static DEFINE_PER_CPU(unsigned long, softlockup_print_ts); /* print timestamp */
 static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog);
+static DEFINE_PER_CPU(bool, softlock_touch_sync);
 
 static int __read_mostly did_panic;
 int __read_mostly softlockup_thresh = 60;
@@ -79,6 +80,12 @@ void touch_softlockup_watchdog(void)
 }
 EXPORT_SYMBOL(touch_softlockup_watchdog);
 
+void touch_softlockup_watchdog_sync(void)
+{
+        __raw_get_cpu_var(softlock_touch_sync) = true;
+        __raw_get_cpu_var(softlockup_touch_ts) = 0;
+}
+
 void touch_all_softlockup_watchdogs(void)
 {
         int cpu;
@@ -118,6 +125,14 @@ void softlockup_tick(void)
         }
 
         if (touch_ts == 0) {
+                if (unlikely(per_cpu(softlock_touch_sync, this_cpu))) {
+                        /*
+                         * If the time stamp was touched atomically
+                         * make sure the scheduler tick is up to date.
+                         */
+                        per_cpu(softlock_touch_sync, this_cpu) = false;
+                        sched_clock_tick();
+                }
                 __touch_softlockup_watchdog();
                 return;
         }