Re: major security bug in reiserfs (may affect SuSE Linux)

[Marc Lehmann <pcg () GOOF COM>]

The bug seems to be confirmed. The patch below does not fix it, it,
however, limits the filename length to a maximum of 255 chars. This might,
of course, make some file inaccessbile but at least one shouldn't be able
to crash the machine or worse, this the forward to bugtraq.

----- Forwarded message from Chris Mason <mason () suse com> -----

Subject: Re: [reiserfs-list] major security bug in reiserfs (may affect SuSE Linux)
From: Chris Mason <mason () suse com>
Date: Tue, 09 Jan 2001 21:23:44 -0500
To: Marc Lehmann <pcg () goof com>
cc: reiserfs-list () namesys com, linux-kernel () vger kernel org,
  vs () namesys botik ru
X-Mailer: Mulberry/2.0.6b1 (Linux/x86)



On Wednesday, January 10, 2001 02:32:09 AM +0100 Marc Lehmann <pcg () goof com> wrote:

> > > EIP; c013f911 <filldir+20b/221>   <=====
> Trace; c013f706 <filldir+0/221>
> Trace; c0136e01 <reiserfs_getblk+2a/16d>

The buffer reiserfs is sending to filldir is big enough for
the huge file name, so I think the real fix should be done in VFSland.

But, in the interest of providing a quick, obviously correct fix, this
reiserfs only patch will refuse to create file names larger
than 255 chars, and skip over any directory entries larger than
255 chars.

--- linux/include/linux/reiserfs_fs.h.1 Tue Jan  9 21:56:18 2001
+++ linux/include/linux/reiserfs_fs.h   Tue Jan  9 21:56:33 2001
@@ -467,7 +467,7 @@
 /* name by bh, ih and entry_num */
 #define B_I_E_NAME(entry_num,bh,ih) ((char *)(bh->b_data + ih->ih_item_location + 
(B_I_DEH(bh,ih)+(entry_num))->deh_location))

-#define REISERFS_MAX_NAME_LEN(block_size) (block_size - BLKH_SIZE - IH_SIZE - DEH_SIZE)        /* -SD_SIZE when entry 
will contain stat data */
+#define REISERFS_MAX_NAME_LEN(block_size) 255

 /* this structure is used for operations on directory entries. It is not a disk structure. */
 /* When reiserfs_find_entry or search_by_entry_key find directory entry, they return filled reiserfs_dir_entry 
structure */
--- linux/fs/reiserfs/dir.c.1   Tue Jan  9 22:06:06 2001
+++ linux/fs/reiserfs/dir.c     Tue Jan  9 22:15:17 2001
@@ -159,6 +159,10 @@
                d_name = B_I_DEH_ENTRY_FILE_NAME (bh, ih, deh);
                d_off = deh->deh_offset;
                d_ino = deh->deh_objectid;
+               if (d_reclen > REISERFS_MAX_NAME_LEN(inode->i_sb->s_blocksize)){
+                   /* it is too big to send back to VFS */
+                   continue ;
+               }
                if (d_reclen <= 32) {
                    local_buf = small_buf ;
                } else {


----- End forwarded message -----

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