From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Alessio Balsini <balsini@android.com>
Date: Wed, 12 May 2021 21:22:02 +0100
Subject: UPSTREAM: fuse: fix matching of FUSE_DEV_IOC_CLONE command

With commit f8425c939663 ("fuse: 32-bit user space ioctl compat for fuse
device") the matching constraints for the FUSE_DEV_IOC_CLONE ioctl command
are relaxed, limited to the testing of command type and number.  As Arnd
noticed, this is wrong as it wouldn't ensure the correctness of the data
size or direction for the received FUSE device ioctl.

Fix by bringing back the comparison of the ioctl received by the FUSE
device to the originally generated FUSE_DEV_IOC_CLONE.

Fixes: f8425c939663 ("fuse: 32-bit user space ioctl compat for fuse device")
Reported-by: Arnd Bergmann <arnd@kernel.org>
Signed-off-by: Alessio Balsini <balsini@android.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Alessio Balsini <balsini@android.com>
Change-Id: I372d8399db6d603ba20ef50528acf6645e4d3c66
(cherry picked from commit 6076f5f341e612152879bfda99f0b76c1953bf0b)
Signed-off-by: Lee Jones <joneslee@google.com>
---
 fs/fuse/dev.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -2283,6 +2283,15 @@ static long fuse_dev_ioctl(struct file *file, unsigned int cmd,
 		}
 		fdput(f);
 		break;
+	case FUSE_DEV_IOC_PASSTHROUGH_OPEN:
+		res = -EFAULT;
+		if (!get_user(oldfd, (__u32 __user *)arg)) {
+			res = -EINVAL;
+			fud = fuse_get_dev(file);
+			if (fud)
+				res = fuse_passthrough_open(fud, oldfd);
+		}
+		break;
 	default:
 		res = -ENOTTY;
 		break;