e2fsprogs: Avoid infinite loop in ext2fs_find_block_device()

[Niu <niu@whamcloud.com>]

hello, Ted

In my rhel5 system, there are lots of loop links in the /dev/.udev/failed folder, which makes the e2fsprogs
'make check' stuck in 't_ext_jnl_rm'. I'm not sure if the loop links are generated by udev defect or misconfiguration,
but anyway, I think the ext2fs_find_block_device() should do some sanity check to avoid infinite loop.

I made a simple patch which breaks the loop when depth reaching 5 in ext2fs_find_block_device(), any comments? Thank you.

>From 5ef3b82266e7fb5edbce4febc4924b0beaccacf1 Mon Sep 17 00:00:00 2001
From: Niu Yawei <niu@whamcloud.com>
Date: Wed, 2 Nov 2011 04:31:11 +0800
Subject: [PATCH] Avoid infinite loop in ext2fs_find_block_device()

The ext2fs_find_block_device() should stop searching when the
directory depth reaching a certain threshold, otherwise, it could
run into infinite loop if there are loop links in the device
directory.

Signed-off-by: Niu Yawei <niu@whamcloud.com>
---
 lib/ext2fs/finddev.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/lib/ext2fs/finddev.c b/lib/ext2fs/finddev.c
index 13ef14b..61f9754 100644
--- a/lib/ext2fs/finddev.c
+++ b/lib/ext2fs/finddev.c
@@ -128,6 +128,7 @@ char *ext2fs_find_block_device(dev_t device)
 	struct dir_list *list = 0, *new_list = 0;
 	struct dir_list *current;
 	char	*ret_path = 0;
+	int    level = 0;
 
 	/*
 	 * Add the starting directories to search...
@@ -154,6 +155,9 @@ char *ext2fs_find_block_device(dev_t device)
 		if (list == 0) {
 			list = new_list;
 			new_list = 0;
+			/* Avoid infinite loop */
+			if (++level > 5)
+				break;
 		}
 	}
 	free_dirlist(&list);
-- 
1.7.1