diff options
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/futex.c | 51 |
1 files changed, 45 insertions, 6 deletions
diff --git a/kernel/futex.c b/kernel/futex.c index 645a4301f1e6..0977ce91129d 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -258,6 +258,18 @@ static void drop_key_refs(union futex_key *key) } } +static inline int get_futex_value_locked(int *dest, int __user *from) +{ + int ret; + + inc_preempt_count(); + ret = __copy_from_user_inatomic(dest, from, sizeof(int)); + dec_preempt_count(); + preempt_check_resched(); + + return ret ? -EFAULT : 0; +} + /* * The hash bucket lock must be held when this is called. * Afterwards, the futex_q must not be accessed. @@ -329,6 +341,7 @@ static int futex_requeue(unsigned long uaddr1, unsigned long uaddr2, int ret, drop_count = 0; unsigned int nqueued; + retry: down_read(¤t->mm->mmap_sem); ret = get_futex_key(uaddr1, &key1); @@ -355,9 +368,20 @@ static int futex_requeue(unsigned long uaddr1, unsigned long uaddr2, before *uaddr1. */ smp_mb(); - if (get_user(curval, (int __user *)uaddr1) != 0) { - ret = -EFAULT; - goto out; + ret = get_futex_value_locked(&curval, (int __user *)uaddr1); + + if (unlikely(ret)) { + /* If we would have faulted, release mmap_sem, fault + * it in and start all over again. + */ + up_read(¤t->mm->mmap_sem); + + ret = get_user(curval, (int __user *)uaddr1); + + if (!ret) + goto retry; + + return ret; } if (curval != *valp) { ret = -EAGAIN; @@ -480,6 +504,7 @@ static int futex_wait(unsigned long uaddr, int val, unsigned long time) int ret, curval; struct futex_q q; + retry: down_read(¤t->mm->mmap_sem); ret = get_futex_key(uaddr, &q.key); @@ -508,9 +533,23 @@ static int futex_wait(unsigned long uaddr, int val, unsigned long time) * We hold the mmap semaphore, so the mapping cannot have changed * since we looked it up in get_futex_key. */ - if (get_user(curval, (int __user *)uaddr) != 0) { - ret = -EFAULT; - goto out_unqueue; + + ret = get_futex_value_locked(&curval, (int __user *)uaddr); + + if (unlikely(ret)) { + /* If we would have faulted, release mmap_sem, fault it in and + * start all over again. + */ + up_read(¤t->mm->mmap_sem); + + if (!unqueue_me(&q)) /* There's a chance we got woken already */ + return 0; + + ret = get_user(curval, (int __user *)uaddr); + + if (!ret) + goto retry; + return ret; } if (curval != val) { ret = -EWOULDBLOCK; |