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

From: Greg Kroah-Hartman
Date: Sun Oct 27 2013 - 17:22:26 EST

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.

Bjorn, don't you have a fix for this problem already done somewhere?


greg k-h
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