linux-kernel - Re: [REGRESSION] coredumps truncated after "new helper: dump

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Date:	Sun, 17 Nov 2013 01:59:02 -0800 (PST)
From:	Peter Wu <lekensteyn@...il.com>
To:	Al Viro <viro@...iv.linux.org.uk>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [REGRESSION] coredumps truncated after "new helper: dump_align()"

On Sunday 17 November 2013 06:19:07 Al Viro wrote:
> On Sat, Nov 16, 2013 at 12:04:08AM +0000, Al Viro wrote:
> > On Fri, Nov 15, 2013 at 10:34:43PM +0100, Peter Wu wrote:
> > 
> >
> > > Unfortunately, this patch still does not fix the issue. I rm'd the
> > > output 
> > > directory just to be sure, but the bug is still there. What does this
> > > commit  do anyway? The commit message is quite vague.
> >
> > 
> >
> > Introduces a helper that used to be open-coded in a bunch of places -
> > pads the coredump to given alignment.  And switches those places
> > to that new helper...
> >
> > 
> >
> > FWIW, I haven't tried that on your config yet, but here (with the patch
> > in my previous mail) I'm seeing a sane-looking coredump -
> > -rw------- 1 root root 315392 Nov 15 17:48 core
> > Different userland, presumably, since that static binary is 684349
> > bytes long.
> >
> > 
> >
> > I'll try to reproduce with your config...
> 
> ... and on your config I'm seeing
> Inited
> Segmentation fault (core dumped)
> [    0.123351] Core size: 315392
> in the log.  Same size, same apparently sane coredump.  Can you check what
> you get on mainline + diff below (combination of dump_align() and locking
> fix)?

Hmm, I cannot reproduce the bug with the two-liner patch you provided before. 
I must have made a mistake with the previous test as the environment is still 
the same.

The bug is fixed with both your two-liner patch and the __kernel_write one.
In addition, the __kernel_write patch removes the lockdep warning reported by 
Dave Jones[1].

Thanks,
Peter

 [1]: http://lkml.org/lkml/2013/11/13/450

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