Re: Ugly rmap NULL ptr deref oopsie on hibernate (was Linux2.6.34-rc3)

[Linus Torvalds]

On Wed, 7 Apr 2010, Borislav Petkov wrote:
> +
> +	if (!anon_vma->head.next) {
> +		printk(KERN_ERR "NULL anon_vma->head.next, page %lu\n",
> +				page_to_pfn(page));
> +
> +		object_err(anon_vma_cachep, page, (u8 *)anon_vma, "NULL next");

Oh, and since the debugging code never triggered ('head.next' wasn't 
actually NULL), you never got here, but the 'page' you passed in to 
object_error() should be the page of the slab allocation, not the page 
associated with the anon_vma.

So it should be something like "virt_to_head_page(anon_vma)" that you pass 
in to object_err().

Not that it matters. I assume it is the fact that SLAB debugging is on 
that actually turns the NULL into a non-NULL thing. Poisoning is not 
active for SLUb's with constructors or RCU-freeing, but things like 
redzoning still are. So enabling SLUB debugging will change the offsets 
within the pages of all the SLUB allocations.  I wonder if that's just 
what caused it to now have that 0x002e2e2e002e2e2e instead of NULL.

		Linus
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/