linux-ext4 - Re: [PATCH 2/2] ext3: ext3

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Date:	Thu, 4 Oct 2012 16:29:00 +0200
From:	Jan Kara <jack@...e.cz>
To:	Carlos Maiolino <cmaiolino@...hat.com>
Cc:	linux-ext4@...r.kernel.org
Subject: Re: [PATCH 2/2] ext3: ext3_bread usage audit [V2]

On Thu 04-10-12 10:57:46, Carlos Maiolino wrote:
> On Thu, Oct 04, 2012 at 03:02:44PM +0200, Jan Kara wrote:
> > On Thu 04-10-12 14:42:12, Jan Kara wrote:
> > > On Tue 02-10-12 23:59:23, Carlos Maiolino wrote:
> > > > This is the ext3 version of the same patch applied to Ext4, where such goal is
> > > > to audit the usage of ext3_bread() due a possible misinterpretion of its return
> > > > value.
> > > > 
> > > > Focused on directory blocks, a NULL value returned from ext3_bread() means a
> > > > hole, which cannot exist into a directory inode. It can pass undetected after a
> > > > fix in an uninitialized error variable.
> > > > 
> > > > The (now) initialized variable into ext3_getblk() may lead to a zero'ed return
> > > > value of ext3_bread() to its callers, which can make the caller do not detect
> > > > the hole in the directory inode.
> > > > 
> > > > This checks for directory holes when buffer_head and error value are both
> > > > zero'ed returning -EIO to their callers
> > > > 
> > > > Some ext3_bread() callers do not needed any changes either because they already
> > > > had its own hole detector paths or because these are deprecaded (like
> > > > dx_show_entries)
> > > > 
> > > > V2: It adds a wrapper function ext3_dir_bread() to check for directory holes
> > > > when reading blocks for a directory inode, and callers of ext3_bread() to read
> > > > directory blocks were replaced by this wrapper.
> > > > 
> > > > Signed-off-by: Carlos Maiolino <cmaiolino@...hat.com>
> > >   Oh, I see you already sent V2. Thanks. I've put the patch to my tree.
> >   Umm, after checking - any reason why you didn't convert also ext3_bread()
> > in dir.c and ext3_bread() in ext3_rename()?
> > 
> I didn't convert some calls for ext3_bread() - like ext3_readdir() -
> because those really don't care about the err value, only about if bh is
> valid or not. I can change this if you want, not a problem from my point.
  Right. I've converted the call in ext3_rename() because there it seems
useful. In ext3_readdir() calling ext3_bread() is better because we want
to be able to read the faulty directory.

								Honza
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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