linux-kernel - Re: [PATCH] 2.6.20.4 fix kernel panic on corrupted reiserfs directory

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Date:	Thu, 5 Apr 2007 21:22:09 +0800
From:	lepton <ytht.net@...il.com>
To:	"Alexander E. Patrakov" <patrakov@....usu.ru>
Cc:	lkm <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] 2.6.20.4 fix kernel panic on corrupted reiserfs directory

Yes, you are right.
I need more work on my trival patch.

On Thu, Apr 05, 2007 at 01:34:42PM +0600, Alexander E. Patrakov wrote:
> lepton wrote:
> >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)
> 
> Is it possible to get a large positive number here due to other fs 
> corruption and bypass your sanity check? If I read the code correctly, this 
> would still oops in the "if" statement just below the part you patched.
> 
> >Signed-off-by: Lepton Wu <ytht.net@...il.com>
> >
> >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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