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Date: Wed, 25 May 2016 02:10:36 +0100
From: Al Viro <viro@ZenIV.linux.org.uk>
To: Matthew McClintock <mmcclint@codeaurora.org>
Cc: Larry Finger <Larry.Finger@lwfinger.net>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: Regression in 4.6.0-git - bisected to commit dd254f5a382c
Message-ID: <20160525011036.GB14480@ZenIV.linux.org.uk>
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On Tue, May 24, 2016 at 07:58:13PM -0500, Matthew McClintock wrote:
> 
> > On May 24, 2016, at 6:41 PM, Al Viro <viro@ZenIV.linux.org.uk> wrote:
> > 
> > Again, I understand what's going on kernel-side; the only tricky part is how
> > to fix it without bringing the nasal daemons back.  I think I have a solution
> > and I'm going to post it tonight if it survives the local beating.  In any
> > case, the testcase above deserves being added to LTP - it's a real regression.
> 
> I’m running a simple busybox rootfs with the following init script:
> 
> https://gist.github.com/7b12fdb5d7def9a835291a79c060fa07
> 
> And inittab:
> 
> https://gist.github.com/5a840b7eaa48f321836125f15147d0e9
> 
> Happy to turn on ftrace, dyndbg, and provide more logs.

Slap the WARN_ON(!size); in the very beginning of iov_iter_advance(), see
where it's triggered...