futex: Protect pid lookup in compat code with RCU

find_task_by_vpid() in compat_sys_get_robust_list() does not require tasklist_lock. It can be protected with rcu_read_lock as done in sys_get_robust_list() already. Signed-off-by: Thomas Gleixner <[email protected]> Cc: Darren Hart <[email protected]> Cc: Peter Zijlstra <[email protected]>
chewitt · Dec 9, 2009 · f409adf · f409adf
1 parent 2b876f9
commit f409adf
Showing 1 changed file with 3 additions and 3 deletions.
diff --git a/kernel/futex_compat.c b/kernel/futex_compat.c
@@ -146,7 +146,7 @@ compat_sys_get_robust_list(int pid, compat_uptr_t __user *head_ptr,
 		struct task_struct *p;
 
 		ret = -ESRCH;
-		read_lock(&tasklist_lock);
+		rcu_read_lock();
 		p = find_task_by_vpid(pid);
 		if (!p)
 			goto err_unlock;
@@ -157,15 +157,15 @@ compat_sys_get_robust_list(int pid, compat_uptr_t __user *head_ptr,
 		    !capable(CAP_SYS_PTRACE))
 			goto err_unlock;
 		head = p->compat_robust_list;
-		read_unlock(&tasklist_lock);
+		rcu_read_unlock();
 	}
 
 	if (put_user(sizeof(*head), len_ptr))
 		return -EFAULT;
 	return put_user(ptr_to_compat(head), head_ptr);
 
 err_unlock:
-	read_unlock(&tasklist_lock);
+	rcu_read_unlock();
 
 	return ret;
 }