Re: [PATCH resend] slub: Add back check for free nonslab objects

[Kefeng Wang]

On 2021/9/27 10:42, Matthew Wilcox wrote:
> On Mon, Sep 27, 2021 at 10:15:38AM +0800, Kefeng Wang wrote:
> > Commit ("0937502af7c9 slub: Add check for kfree() of non slab objects.")
> > add the ability, which should be needed in any configs to catch the
> > invalid free, they even could be potential issue, eg, memory corruption,
> > use after free and double-free, so replace VM_BUG_ON_PAGE to WARN_ON, and
> > add dump_page() to help use to debug the issue.
> Is dump_page() really the best way to catch such a thing?  I would have
> thought that printing the address of 'object' would be more helpful.

With no vmcore, dump_page() do help us to find a memory corruption issue.

We could add 'object ' address print too.

> > @@ -3522,7 +3522,8 @@ static inline void free_nonslab_page(struct page *page, void *object)
> >   {
> >   	unsigned int order = compound_order(page);
> >   
> > -	VM_BUG_ON_PAGE(!PageCompound(page), page);
> > +	if (WARN_ON(!PageCompound(page)))
> > +		dump_page(page, "invalid free nonslab page");
> .