futex: Take mmap_sem for get_user_pages in fault_in_user_writeable

get_user_pages() must be called with mmap_sem held. Signed-off-by: Andi Kleen <[email protected]> Cc: [email protected] Cc: Andrew Morton <[email protected]> Cc: Nick Piggin <[email protected]> Cc: Darren Hart <[email protected]> Cc: Peter Zijlstra <[email protected]> LKML-Reference: <[email protected]> Signed-off-by: Thomas Gleixner <[email protected]>
iegor · Dec 8, 2009 · 722d017 · 722d017
1 parent f5754bf
commit 722d017
Showing 1 changed file with 8 additions and 2 deletions.
diff --git a/kernel/futex.c b/kernel/futex.c
@@ -304,8 +304,14 @@ void put_futex_key(int fshared, union futex_key *key)
  */
 static int fault_in_user_writeable(u32 __user *uaddr)
 {
-	int ret = get_user_pages(current, current->mm, (unsigned long)uaddr,
-				 1, 1, 0, NULL, NULL);
+	struct mm_struct *mm = current->mm;
+	int ret;
+
+	down_read(&mm->mmap_sem);
+	ret = get_user_pages(current, mm, (unsigned long)uaddr,
+			     1, 1, 0, NULL, NULL);
+	up_read(&mm->mmap_sem);
+
 	return ret < 0 ? ret : 0;
 }