pipe: Fix memory leaks in create_pipe_files()

Calling pipe2() with O_NOTIFICATION_PIPE could results in memory
leaks unless watch_queue_init() is successful.

In case of watch_queue_init() failure in pipe2() we are left
with inode and pipe_inode_info instances that need to be freed. That
failure exit has been introduced in commit c73be61cede5 ("pipe: Add
general notification queue support") and its handling should've been
identical to nearby treatment of alloc_file_pseudo() failures - it
is dealing with the same situation. As it is, the mainline kernel
leaks in that case.

Another problem is that CONFIG_WATCH_QUEUE and !CONFIG_WATCH_QUEUE
cases are treated differently (and the former leaks just pipe_inode_info,
the latter - both pipe_inode_info and inode).

Fixed by providing a dummy wacth_queue_init() in !CONFIG_WATCH_QUEUE
case and by having failures of wacth_queue_init() handled the same way
we handle alloc_file_pseudo() ones.

Fixes: c73be61cede5 ("pipe: Add general notification queue support")
Signed-off-by: Qian Cai <[e-mail]>
Signed-off-by: Al Viro <[e-mail]>

fs/pipe.c

···
 {
 	struct inode *inode = get_pipe_inode();
 	struct file *f;
+	int error;
 
 	if (!inode)
 		return -ENFILE;
 
 	if (flags & O_NOTIFICATION_PIPE) {
-#ifdef CONFIG_WATCH_QUEUE
-		if (watch_queue_init(inode->i_pipe) < 0) {
+		error = watch_queue_init(inode->i_pipe);
+		if (error) {
+			free_pipe_info(inode->i_pipe);
 			iput(inode);
-			return -ENOMEM;
+			return error;
 		}
-#else
-		return -ENOPKG;
-#endif
 	}
 
 	f = alloc_file_pseudo(inode, pipe_mnt, "",

include/linux/watch_queue.h

···
  */
 #define watch_sizeof(STRUCT) (sizeof(STRUCT) << WATCH_INFO_LENGTH__SHIFT)
 
+#else
+static inline int watch_queue_init(struct pipe_inode_info *pipe)
+{
+	return -ENOPKG;
+}
+
 #endif
 
 #endif /* _LINUX_WATCH_QUEUE_H */