Re: [BUG 3.12.rc4] Oops: unable to handle kernel paging requestduring shutdown

[Veaceslav Falico]

On Mon, Oct 28, 2013 at 11:35:09AM -0600, Bjorn Helgaas wrote:
> On Mon, Oct 28, 2013 at 11:30 AM, Veaceslav Falico <vfalico@xxxxxxxxxx> wrote:
> > On Mon, Oct 28, 2013 at 11:23:41AM -0600, Bjorn Helgaas wrote:
> > > [+cc Veaceslav]
> > >
> > > On Sun, Oct 27, 2013 at 3:24 PM, Greg Kroah-Hartman
> > > <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
> > > > On Sun, Oct 27, 2013 at 09:13:29PM +0000, Linus Torvalds wrote:
> > > > > .. and one more case of freeing a delayed work object (likely a kobject
> > > > > again):
> > > > >
> > > > > This time it looks like it's in the PCI layer, freeing the msi irq
> > > > > information.
> > > > >
> > > > > It looks like that code simply does
> > > > >
> > > > >     kobject_del(&entry->kobj);
> > > > >     kobject_put(&entry->kobj);
> > > > >     list_del(&entry->list);
> > > > >     kfree(entry);
> > > > >
> > > > > and the problem is that the "entry->kobj" may have *other* references
> > > > > to it, thanks to people accessing it through /sys, so despite doing a
> > > > > kojbect_del/kobject_put(), it's not at all ok to then do a "kfree()"
> > > > > on it. The embedded kobj might still be in use.
> > > > >
> > > > > Afaik, that code should do the kfree() on the kobject in the _release_
> > > > > method, not synchronously like that.
> > > > >
> > > > > We already have a msi_kobj_release(), I'm wondering why that doesn't
> > > > > do the kfree().
> > > > >
> > > > > Bjorn? Yinghai? Greg, comments about that msi kobj usage?
> > > >
> > > >
> > > > Ick, it really should be doing a kfree() in the release only.  Bjorn has
> > > > had a bunch of changes in this area recently, perhaps they are in
> > > > linux-next waiting for 3.13, and I've talked to him about getting rid of
> > > > all of the kobjects for msi files, as I don't think it's needed at all.
> > >
> > >
> > > IIRC, you said you might take a look at converting this to attributes
> > > on the train back home, so I haven't looked into it myself :)
> > >
> > > > Bjorn, don't you have a fix for this problem already done somewhere?
> > >
> > >
> > > Yep, this is clearly wrong, and Veaceslav has a patch that moves the
> > > kfree() to the release function.  I've been waiting for a consolidated
> > > repost of all his MSI-related fixes, but maybe he's been waiting for
> > > *me*.
> >
> >
> > https://lkml.org/lkml/2013/10/9/170
> >
> > My patchset is ready to be applied, in its v2 state.
> >
> > Except that the bits with kobject_del() (theoretical race) - which are done
> > in your patch "kobject: remove kset from sysfs immediately in
> > kset_unregister()", though I didn't see it accepted.
> >
> > Should I re-send the patchset?
>
> Can you please repost it?  That will be easier for me than digging
> individual messages out of the archives.  Thanks, and sorry for my
> confusion.

Will rebase and repost, sorry for all the noise about it :).

Thank you!

> Bjorn
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