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

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Message-ID: <4614A692.5020605@ums.usu.ru>
Date:	Thu, 05 Apr 2007 13:34:42 +0600
From:	"Alexander E. Patrakov" <patrakov@....usu.ru>
To:	lepton <ytht.net@...il.com>, lkm <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] 2.6.20.4 fix kernel panic on corrupted reiserfs directory

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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