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

* 'futexes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  futex: Fix the write access fault problem for real
This commit is contained in:
Linus Torvalds 2009-06-24 13:33:19 -07:00
parent ba52270d18 d0725992c8
commit bd453cd487
1 changed files with 24 additions and 21 deletions
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45
kernel/futex.c
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@ -284,6 +284,25 @@ void put_futex_key(int fshared, union futex_key *key)
drop_futex_key_refs(key);
}
/*
* fault_in_user_writeable - fault in user address and verify RW access
* @uaddr: pointer to faulting user space address
*
* Slow path to fixup the fault we just took in the atomic write
* access to @uaddr.
*
* We have no generic implementation of a non destructive write to the
* user address. We know that we faulted in the atomic pagefault
* disabled section so we can as well avoid the #PF overhead by
* calling get_user_pages() right away.
*/
static int fault_in_user_writeable(u32 __user *uaddr)
{
int ret = get_user_pages(current, current->mm, (unsigned long)uaddr,
sizeof(*uaddr), 1, 0, NULL, NULL);
return ret < 0 ? ret : 0;
}
/**
* futex_top_waiter() - Return the highest priority waiter on a futex
* @hb: the hash bucket the futex_q's reside in
@ -896,7 +915,6 @@ retry:
retry_private:
op_ret = futex_atomic_op_inuser(op, uaddr2);
if (unlikely(op_ret < 0)) {
u32 dummy;
double_unlock_hb(hb1, hb2);
@ -914,7 +932,7 @@ retry_private:
goto out_put_keys;
}
ret = get_user(dummy, uaddr2);
ret = fault_in_user_writeable(uaddr2);
if (ret)
goto out_put_keys;
@ -1204,7 +1222,7 @@ retry_private:
double_unlock_hb(hb1, hb2);
put_futex_key(fshared, &key2);
put_futex_key(fshared, &key1);
ret = get_user(curval2, uaddr2);
ret = fault_in_user_writeable(uaddr2);
if (!ret)
goto retry;
goto out;
@ -1482,7 +1500,7 @@ retry:
handle_fault:
spin_unlock(q->lock_ptr);
ret = get_user(uval, uaddr);
ret = fault_in_user_writeable(uaddr);
spin_lock(q->lock_ptr);
@ -1807,7 +1825,6 @@ static int futex_lock_pi(u32 __user *uaddr, int fshared,
{
struct hrtimer_sleeper timeout, *to = NULL;
struct futex_hash_bucket *hb;
u32 uval;
struct futex_q q;
int res, ret;
@ -1909,16 +1926,9 @@ out:
return ret != -EINTR ? ret : -ERESTARTNOINTR;
uaddr_faulted:
/*
* We have to r/w *(int __user *)uaddr, and we have to modify it
* atomically. Therefore, if we continue to fault after get_user()
* below, we need to handle the fault ourselves, while still holding
* the mmap_sem. This can occur if the uaddr is under contention as
* we have to drop the mmap_sem in order to call get_user().
*/
queue_unlock(&q, hb);
ret = get_user(uval, uaddr);
ret = fault_in_user_writeable(uaddr);
if (ret)
goto out_put_key;
@ -2013,17 +2023,10 @@ out:
return ret;
pi_faulted:
/*
* We have to r/w *(int __user *)uaddr, and we have to modify it
* atomically. Therefore, if we continue to fault after get_user()
* below, we need to handle the fault ourselves, while still holding
* the mmap_sem. This can occur if the uaddr is under contention as
* we have to drop the mmap_sem in order to call get_user().
*/
spin_unlock(&hb->lock);
put_futex_key(fshared, &key);
ret = get_user(uval, uaddr);
ret = fault_in_user_writeable(uaddr);
if (!ret)
goto retry;