linux-kernel - Re: [PATCH] Check for Null return of function of affs_bread in function affs

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Message-ID: <CAPDOMVhr27nDZ8PD3Cw0SUCUMu6Vg3scekX2gAOOi_aP60aXSQ@mail.gmail.com>
Date:	Fri, 20 Jun 2014 22:55:07 -0400
From:	Nick Krause <xerofoify@...il.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Dan Carpenter <dan.carpenter@...cle.com>,
	viro@...iv.linux.org.uk, fabf@...net.be,
	kirill.shutemov@...ux.intel.com, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Check for Null return of function of affs_bread in
 function affs_truncate

Fair enough if somebody is running this file system I would be
happy to have someone test my code in order to fix this.
Cheers Nick

On Fri, Jun 20, 2014 at 10:38 PM, Andrew Morton
<akpm@...ux-foundation.org> wrote:
> On Fri, 20 Jun 2014 22:25:47 -0400 Nick Krause <xerofoify@...il.com> wrote:
>
>> If you have any ideas about what is better
>> please let me known.
>
> I think the proposed patch was not a good one - it will cause truncate
> to silently return, probably leaving the fs in an inconsistent state.
> Neither the user nor the running application know this happened so they
> will just keep on modifying the filesystem, possibly mangling it
> further.
>
> The code as it stands at present is better - if bread() fails we'll get
> a nice solid oops and the current app will be terminated (at least).
> As we're in truncate it's quite possible that the entire fs will get
> wedged up due to now-permanently-held i_mutex, which is even better.
>
>
> As for the best fix, umm, hard.  We're pretty screwed if we cannot read
> that block at this code site.  Perhaps emit loud printks, forcibly turn
> the fs read-only then return -EIO/-ENOMEM/etc from the truncate.  Such
> a change would require runtime testing, with some form of developer fault
> injection.
>
>
>
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