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Date: Mon, 10 Oct 2005 18:46:05 -0300
From: Glauber de Oliveira Costa <glommer@br.ibm.com>
To: Anton Altaparmakov <aia21@cam.ac.uk>
Cc: glommer@br.ibm.com, linux-kernel@vger.kernel.org,
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Subject: Re: [PATCH] Use of getblk differs between locations
Message-ID: <20051010214605.GA11427@br.ibm.com>
References: <20051010204517.GA30867@br.ibm.com> <Pine.LNX.4.64.0510102217200.6247@hermes-1.csi.cam.ac.uk>
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On Mon, Oct 10, 2005 at 10:20:07PM +0100, Anton Altaparmakov wrote:
> Hi,
> 
> On Mon, 10 Oct 2005, Glauber de Oliveira Costa wrote:
> > I've just noticed that the use of sb_getblk differs between locations
> > inside the kernel. To be precise, in some locations there are tests
> > against its return value, and in some places there are not.
> > 
> > According to the comments in __getblk definition, the tests are not
> > necessary, as the function always return a buffer_head (maybe a wrong
> > one),
> 
> If you had read the source code rather than just the comments you would 
> have seen that this is not true.  It can return NULL (see 
> fs/buffer.c::__getblk_slow()).  Certainly I would prefer to keep the 
> checks in NTFS, please.  They may only be good for catching bugs but I 
> like catching bugs rather than segfaulting due to a NULL dereference.

I did. But I did not see this specifically, for sure. What takes us to
the opposite problem: A lot of places do not check for the return value
of getblk (Almost half of them, I'd say), and may thus lead to a 
dereferencing  of a NULL pointer.

Does anyone else have any comments on that?

> Best regards,
Thanks,
> 	Anton
Glauber

> -- 
> Anton Altaparmakov <aia21 at cam.ac.uk> (replace at with @)
> Unix Support, Computing Service, University of Cambridge, CB2 3QH, UK
> Linux NTFS maintainer / IRC: #ntfs on irc.freenode.net
> WWW: http://linux-ntfs.sf.net/ & http://www-stu.christs.cam.ac.uk/~aia21/
> 

-- 
=====================================
Glauber de Oliveira Costa
IBM Linux Technology Center - Brazil
glommer@br.ibm.com
=====================================
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