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Message-ID: <20130916210503.GQ25896@mwanda>
Date: Tue, 17 Sep 2013 00:05:04 +0300
From: Dan Carpenter <dan.carpenter@...cle.com>
To: Joseph Salisbury <joseph.salisbury@...onical.com>
Cc: thomas@...3r.de, Jiri Kosina <jkosina@...e.cz>, list@...osl.org,
Haiyang Zhang <haiyangz@...rosoft.com>,
LKML <linux-kernel@...r.kernel.org>, open@...osl.org,
HID CORE LAYER <linux-input@...r.kernel.org>,
devel@...uxdriverproject.org
Subject: Re: [v3.11][Regression] HID: hyperv: convert alloc+memcpy to memdup
On Mon, Sep 16, 2013 at 04:49:29PM -0400, Joseph Salisbury wrote:
> On 09/16/2013 04:38 PM, Dan Carpenter wrote:
> > On Mon, Sep 16, 2013 at 01:42:35PM -0400, Joseph Salisbury wrote:
> >> Reverting the patch changes the driver back to useing kzalloc() and
> >> memcpy() instead of kmemdup. Doing so has uncovered another bug, which
> >> causes an oops on memcpy()[1]. We are in the process of bisecting that
> >> one now and will provide the results.
> > The two bugs are the same it's that the code has shifted a little. Mark
> > the commit as buggy and continue with the git bisect.
> >
> > regards,
> > dan carpenter
> Can you explain a little further? Mark commit a4a23f6 as bad? An
> initial bisect already reported that was the first bad commit, so it
> can't be marked bad. The oops on memcpy() happens after commit a4a23f6
> is reverted. The oops on memcpy() did not happen before a4a23f6 was
> committed, so I assume this new oops was introduced by a change later.
>
> Right now I'm bisecting down the oops on memcpy() by updating the bisect
> with good or bad, depending if the test kernel hit the oops. I then
> revert a4a23f6, so that revert is the HEAD of the tree each time before
> building the kernel again(As long as the commit spit out by bisect is
> after when a4a23f6 was introduced).
Yep. Please continue bisecting the memcpy() oops.
kmemdup() is just a kzalloc() followed by a memcpy(). When we split it
apart by reverting the patch then we would expect the oops to move to
the memcpy() part. Somehow "desc" is a bogus pointer, but I don't
immediately see how that is possible.
regards,
dan carpenter
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