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 80cc1b35d46043c16bc456e0cadf61e76c281d52..ebb5e37455a07acd86f5fbf1b76d474e99b937fb 100644 (file)
--- 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);