fuse: always allow query of st_dev

Fuse mounts without "allow_other" are off-limits to all non-owners. Yet it makes sense to allow querying st_dev on the root, since this value is provided by the kernel, not the userspace filesystem. Allow statx(2) with a zero request mask to succeed on a fuse mounts for all users. Reported-by: Nikolaus Rath <[email protected]> Signed-off-by: Miklos Szeredi <[email protected]>
nelseric · May 19, 2020 · 5157da2 · 5157da2
1 parent 614c026
commit 5157da2
Showing 1 changed file with 11 additions and 1 deletion.
diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
@@ -1689,8 +1689,18 @@ static int fuse_getattr(const struct path *path, struct kstat *stat,
 	struct inode *inode = d_inode(path->dentry);
 	struct fuse_conn *fc = get_fuse_conn(inode);
 
-	if (!fuse_allow_current_process(fc))
+	if (!fuse_allow_current_process(fc)) {
+		if (!request_mask) {
+			/*
+			 * If user explicitly requested *nothing* then don't
+			 * error out, but return st_dev only.
+			 */
+			stat->result_mask = 0;
+			stat->dev = inode->i_sb->s_dev;
+			return 0;
+		}
 		return -EACCES;
+	}
 
 	return fuse_update_get_attr(inode, NULL, stat, request_mask, flags);
 }