From 8ed1f0e22f49ef42e63875fd2529389a32ff3566 Mon Sep 17 00:00:00 2001
From: Jann Horn <jann@thejh.net>
Date: Sun, 16 Aug 2015 20:27:01 +0200
Subject: fs/fuse: fix ioctl type confusion

fuse_dev_ioctl() performed fuse_get_dev() on a user-supplied fd,
leading to a type confusion issue. Fix it by checking file->f_op.

Signed-off-by: Jann Horn <jann@thejh.net>
Acked-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 80cc1b3..ebb5e37 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -2246,7 +2246,15 @@ static long fuse_dev_ioctl(struct file *file, unsigned int cmd,
 
 			err = -EINVAL;
 			if (old) {
-				struct fuse_dev *fud = fuse_get_dev(old);
+				struct fuse_dev *fud = NULL;
+
+				/*
+				 * Check against file->f_op because CUSE
+				 * uses the same ioctl handler.
+				 */
+				if (old->f_op == file->f_op &&
+				    old->f_cred->user_ns == file->f_cred->user_ns)
+					fud = fuse_get_dev(old);
 
 				if (fud) {
 					mutex_lock(&fuse_mutex);
-- 
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