fuse: fix allowing operations

The following operation didn't check if sending the request was allowed:

  setattr
  listxattr
  statfs

Some other operations don't explicitly do the check, but VFS calls
->permission() which checks this.
Signed-off-by: NMiklos Szeredi <mszeredi@suse.cz>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

fs/fuse/dir.c

@@ -721,7 +721,7 @@ static int fuse_refresh_attributes(struct inode *inode)
  * for which the owner of the mount has ptrace privilege.  This
  * excludes processes started by other users, suid or sgid processes.
  */
-static int fuse_allow_task(struct fuse_conn *fc, struct task_struct *task)
+int fuse_allow_task(struct fuse_conn *fc, struct task_struct *task)
 {
 	if (fc->flags & FUSE_ALLOW_OTHER)
 		return 1;
@@ -1005,6 +1005,9 @@ static int fuse_setattr(struct dentry *entry, struct iattr *attr)
 	struct fuse_attr_out outarg;
 	int err;
 
+	if (!fuse_allow_task(fc, current))
+		return -EACCES;
+
 	if (fc->flags & FUSE_DEFAULT_PERMISSIONS) {
 		err = inode_change_ok(inode, attr);
 		if (err)
@@ -1172,6 +1175,9 @@ static ssize_t fuse_listxattr(struct dentry *entry, char *list, size_t size)
 	struct fuse_getxattr_out outarg;
 	ssize_t ret;
 
+	if (!fuse_allow_task(fc, current))
+		return -EACCES;
+
 	if (fc->no_listxattr)
 		return -EOPNOTSUPP;
 

fs/fuse/fuse_i.h

@@ -565,3 +565,8 @@ void fuse_ctl_remove_conn(struct fuse_conn *fc);
  * Is file type valid?
  */
 int fuse_valid_type(int m);
+
+/**
+ * Is task allowed to perform filesystem operation?
+ */
+int fuse_allow_task(struct fuse_conn *fc, struct task_struct *task);

fs/fuse/inode.c

@@ -287,6 +287,11 @@ static int fuse_statfs(struct dentry *dentry, struct kstatfs *buf)
 	struct fuse_statfs_out outarg;
 	int err;
 
+	if (!fuse_allow_task(fc, current)) {
+		buf->f_type = FUSE_SUPER_MAGIC;
+		return 0;
+	}
+
 	req = fuse_get_req(fc);
 	if (IS_ERR(req))
 		return PTR_ERR(req);