Merge branch 'linus' into core/urgent

[pandora-kernel.git] / kernel / futex.c

diff --git a/kernel/futex.c b/kernel/futex.c
index 3fbc76c..11cbe05 100644 (file)
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -218,6 +218,8 @@ static void drop_futex_key_refs(union futex_key *key)
  * @uaddr:     virtual address of the futex
  * @fshared:   0 for a PROCESS_PRIVATE futex, 1 for PROCESS_SHARED
  * @key:       address where result is stored.
+ * @rw:                mapping needs to be read/write (values: VERIFY_READ,
+ *              VERIFY_WRITE)
  *
  * Returns a negative error code or 0
  * The key words are stored in *key on success.
@@ -229,12 +231,12 @@ static void drop_futex_key_refs(union futex_key *key)
  * lock_page() might sleep, the caller should not hold a spinlock.
  */
 static int
-get_futex_key(u32 __user *uaddr, int fshared, union futex_key *key)
+get_futex_key(u32 __user *uaddr, int fshared, union futex_key *key, int rw)
 {
        unsigned long address = (unsigned long)uaddr;
        struct mm_struct *mm = current->mm;
        struct page *page, *page_head;
-       int err;
+       int err, ro = 0;
 
        /*
         * The futex address must be "naturally" aligned.
@@ -262,8 +264,18 @@ get_futex_key(u32 __user *uaddr, int fshared, union futex_key *key)
 
 again:
        err = get_user_pages_fast(address, 1, 1, &page);
+       /*
+        * If write access is not required (eg. FUTEX_WAIT), try
+        * and get read-only access.
+        */
+       if (err == -EFAULT && rw == VERIFY_READ) {
+               err = get_user_pages_fast(address, 1, 0, &page);
+               ro = 1;
+       }
        if (err < 0)
                return err;
+       else
+               err = 0;
 
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
        page_head = page;
@@ -305,6 +317,13 @@ again:
        if (!page_head->mapping) {
                unlock_page(page_head);
                put_page(page_head);
+               /*
+               * ZERO_PAGE pages don't have a mapping. Avoid a busy loop
+               * trying to find one. RW mapping would have COW'd (and thus
+               * have a mapping) so this page is RO and won't ever change.
+               */
+               if ((page_head == ZERO_PAGE(address)))
+                       return -EFAULT;
                goto again;
        }
 
@@ -316,6 +335,15 @@ again:
         * the object not the particular process.
         */
        if (PageAnon(page_head)) {
+               /*
+                * A RO anonymous page will never change and thus doesn't make
+                * sense for futex operations.
+                */
+               if (ro) {
+                       err = -EFAULT;
+                       goto out;
+               }
+
                key->both.offset |= FUT_OFF_MMSHARED; /* ref taken on mm */
                key->private.mm = mm;
                key->private.address = address;
@@ -327,9 +355,10 @@ again:
 
        get_futex_key_refs(key);
 
+out:
        unlock_page(page_head);
        put_page(page_head);
-       return 0;
+       return err;
 }
 
 static inline void put_futex_key(union futex_key *key)
@@ -355,8 +384,8 @@ static int fault_in_user_writeable(u32 __user *uaddr)
        int ret;
 
        down_read(&mm->mmap_sem);
-       ret = get_user_pages(current, mm, (unsigned long)uaddr,
-                            1, 1, 0, NULL, NULL);
+       ret = fixup_user_fault(current, mm, (unsigned long)uaddr,
+                              FAULT_FLAG_WRITE);
        up_read(&mm->mmap_sem);
 
        return ret < 0 ? ret : 0;
@@ -940,7 +969,7 @@ futex_wake(u32 __user *uaddr, unsigned int flags, int nr_wake, u32 bitset)
        if (!bitset)
                return -EINVAL;
 
-       ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &key);
+       ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &key, VERIFY_READ);
        if (unlikely(ret != 0))
                goto out;
 
@@ -986,10 +1015,10 @@ futex_wake_op(u32 __user *uaddr1, unsigned int flags, u32 __user *uaddr2,
        int ret, op_ret;
 
 retry:
-       ret = get_futex_key(uaddr1, flags & FLAGS_SHARED, &key1);
+       ret = get_futex_key(uaddr1, flags & FLAGS_SHARED, &key1, VERIFY_READ);
        if (unlikely(ret != 0))
                goto out;
-       ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2);
+       ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2, VERIFY_WRITE);
        if (unlikely(ret != 0))
                goto out_put_key1;
 
@@ -1243,10 +1272,11 @@ retry:
                pi_state = NULL;
        }
 
-       ret = get_futex_key(uaddr1, flags & FLAGS_SHARED, &key1);
+       ret = get_futex_key(uaddr1, flags & FLAGS_SHARED, &key1, VERIFY_READ);
        if (unlikely(ret != 0))
                goto out;
-       ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2);
+       ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2,
+                           requeue_pi ? VERIFY_WRITE : VERIFY_READ);
        if (unlikely(ret != 0))
                goto out_put_key1;
 
@@ -1790,7 +1820,7 @@ static int futex_wait_setup(u32 __user *uaddr, u32 val, unsigned int flags,
         * while the syscall executes.
         */
 retry:
-       ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &q->key);
+       ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &q->key, VERIFY_READ);
        if (unlikely(ret != 0))
                return ret;
 
@@ -1941,7 +1971,7 @@ static int futex_lock_pi(u32 __user *uaddr, unsigned int flags, int detect,
        }
 
 retry:
-       ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &q.key);
+       ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &q.key, VERIFY_WRITE);
        if (unlikely(ret != 0))
                goto out;
 
@@ -2060,7 +2090,7 @@ retry:
        if ((uval & FUTEX_TID_MASK) != vpid)
                return -EPERM;
 
-       ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &key);
+       ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &key, VERIFY_WRITE);
        if (unlikely(ret != 0))
                goto out;
 
@@ -2249,7 +2279,7 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags,
        debug_rt_mutex_init_waiter(&rt_waiter);
        rt_waiter.task = NULL;
 
-       ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2);
+       ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2, VERIFY_WRITE);
        if (unlikely(ret != 0))
                goto out;