linux-kernel - Re: partition sysfs OOPS in current GIT

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Date:	Wed, 6 Feb 2008 21:47:38 -0800
From:	Greg KH <gregkh@...e.de>
To:	David Miller <davem@...emloft.net>
Cc:	linux-kernel@...r.kernel.org, kay.sievers@...y.org
Subject: Re: partition sysfs OOPS in current GIT

On Wed, Feb 06, 2008 at 08:06:18PM -0800, David Miller wrote:
> 
> Greg, I'm pretty sure I know what's happening.
> 
> For whatever reason we're invoking dev_attr_show() on attribute_group
> objects.

Ugh, that makes sense.

> The reason it probably only crashes on sparc64 is because perhaps at
> that dev_attr->show offset on x86 there are zero bytes there instead
> of a pointer, so the NULL check here in dev_attr_show() masks the bug.
> 
> The problem with all of this "container_of() this", "container_of()
> that" is that we lose real type checking.  So unless we add magic
> cookies to verify or other hacks, functions never really know if the
> container they are being passed really is a subset object of the type
> they expect.

We are supposed to be careful about this, but bad things are known to
happen :)

> Can you read the code instead of asking more information from me to
> try and figure out why the attribute showing paths might be
> misconfigured for these block device objects after the changeset in
> question?  I can do this, but you're more likely to find the problem
> quickly than I am.

Yes, I'll look into it tonight if I get this -stable push out in time,
or if not, first thing in the morning.

> I redid the bisect to make sure it absolutely was that specific
> changeset, and it is.

Thanks for doing that, I'll let you know when I have a patch to test.

greg k-h
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