Re: [REGRESSION] coredumps truncated after "new helper: dump_align()"

Peter Wu
2013-11-17T09:59:09Z

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