[PATCH] 2.6.20.4 fix kernel panic on corrupted reiserfs directory

[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@gmail.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

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

[Alexander E. Patrakov]

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@gmail.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

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

[lepton]

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@gmail.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