[PATCH] 2.6.22.6 fix kernel panic on corrupted reiserfs directory

[lepton <ytht.net@gmail.com>]

Hi,
  When reading corrupted reiserfs directory data, d_reclen
  could be a negative number or a big positive number, this
  can lead to kernel panic or oop.
  The following patch adds a sanity check. (against 2.6.20.4)

Signed-off-by: Lepton Wu <ytht.net@gmail.com>

diff -X linux-2.6.22.6-lepton/Documentation/dontdiff -pru linux-2.6.22.6/fs/reiserfs/dir.c linux-2.6.22.6-lepton/fs/reiserfs/dir.c
--- linux-2.6.22.6/fs/reiserfs/dir.c	2007-09-14 17:41:15.000000000 +0800
+++ linux-2.6.22.6-lepton/fs/reiserfs/dir.c	2007-09-14 18:02:10.000000000 +0800
@@ -121,6 +121,16 @@ static int reiserfs_readdir(struct file 
 					continue;
 				d_reclen = entry_length(bh, ih, entry_num);
 				d_name = B_I_DEH_ENTRY_FILE_NAME(bh, ih, deh);
+
+				if (d_reclen <= 0 ||
+				    d_name + d_reclen > bh->b_data + bh->b_size) {
+					/* There is corrupted data in entry,
+					 * We'd better stop here */
+					pathrelse(&path_to_entry);
+					ret = -EIO;
+					goto out;
+				}
+		
 				if (!d_name[d_reclen - 1])
 					d_reclen = strlen(d_name);