linux-ext4 - Re: ext3: ext4: Using uninitialized value

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <0E811115-22DB-4D20-AE03-428037E1429C@dilger.ca>
Date:	Wed, 13 Oct 2010 12:56:33 -0600
From:	Andreas Dilger <adilger@...ger.ca>
To:	Eric Sandeen <sandeen@...hat.com>
Cc:	Roman Borisov <ext-roman.borisov@...ia.com>,
	linux-ext4@...r.kernel.org
Subject: Re: ext3: ext4: Using uninitialized value

On 2010-10-13, at 10:13, Eric Sandeen wrote:
> On 10/13/2010 09:40 AM, Roman Borisov wrote:
>> Hello,
>> 
>> Could you clarify is there a bug in fs/ext4/namei.c,
>> ext4_dx_find_entry() and fs/ext4/namei.c, ext3_dx_find_entry()?
> 
> that was introduced with:
> 
> commit acfa1823d33859b0db77701726c9ca5ccc6e6f25
> Author: Andreas Dilger <adilger@...sterfs.com>
> Date:   Thu Jun 23 00:09:45 2005 -0700
> 
>   [PATCH] Support for dx directories in ext3_get_parent (NFSD)
> 
> so maybe Andreas knows offhand ;)  but I think:

Your analysis is correct.  I agree it's a bit convoluted, but it avoids replicating a bunch of code.

>> static struct buffer_head * ext3_dx_find_entry(struct inode *dir,
>> ...
>>       if (namelen > 2 || name[0] != '.'|| (namelen == 2 && name[1] != '.'))
>>        } else {
> 
> so here it -is- "." or ".." -
> 
>>               frame = frames;
>>               frame->bh = NULL;                       /* for dx_release() */
>>               frame->at = (struct dx_entry *)frames;  /* hack for zero entry*/
>>               dx_set_block(frame->at, 0);             /* dx_root block is 0 */
>>               if (!(bh = ext3_bread (NULL,dir, block, 0, err)))
>>                       goto errout;
> 
> so we look up block 0 in the dir inode
> 
>>                       if (ext3_match(namelen, name, de)) {
> 
> here we should find the . or .. (it's always going to be there, right?)

Right - it is important to note that the index root block is a "fake" directory block which has just the "." and ".." entries at the beginning (with the ".." spanning the rest of the block), and the rest of the block is holding the index entries.  For a directory index to even exist, it HAS to have the "." and ".." entries in the first block, or there is no place to put the index.

Cheers, Andreas





--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html