[PATCH] 2.6.20.4 fix kernel panic on corrupted reiserfs directory

[lepton]

Hi,
  When reading corrupted reiserfs directory data, d_reclen
  could be a negative number, then memcpy will overflow
  kernel stack. This can lead to kernel panic.
  The following patch adds a sanity check. (against 2.6.20.4)
 
Signed-off-by: Lepton Wu <ytht.net@xxxxxxxxx>

diff -pru linux-2.6/fs/reiserfs/dir.c linux-2.6-lepton/fs/reiserfs/dir.c
--- linux-2.6/fs/reiserfs/dir.c	2007-02-20 14:34:32.000000000 +0800
+++ linux-2.6-lepton/fs/reiserfs/dir.c	2007-04-05 14:35:58.000000000 +0800
@@ -121,6 +121,11 @@ static int reiserfs_readdir(struct file 
 					/* it is hidden entry */
 					continue;
 				d_reclen = entry_length(bh, ih, entry_num);
+				if (d_reclen < 0) {
+					pathrelse(&path_to_entry);
+					ret = -EIO;
+					goto out;
+				}
 				d_name = B_I_DEH_ENTRY_FILE_NAME(bh, ih, deh);
 				if (!d_name[d_reclen - 1])
 					d_reclen = strlen(d_name);
O
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