Re: [PATCH v2] mm: teach dump_page() to correctly output poisoned struct pages
On Mon, 2 Jul 2018 14:05:36 -0400 Pavel Tatashin
wrote:
> If struct page is poisoned, and uninitialized access is detected via
> PF_POISONED_CHECK(page) dump_page() is called to output the page. But,
> the dump_page() itself accesses struct page to determine how to print
> it, and therefore gets into a recursive loop.
>
> For example:
> dump_page()
> __dump_page()
> PageSlab(page)
>PF_POISONED_CHECK(page)
> VM_BUG_ON_PGFLAGS(PagePoisoned(page), page)
> dump_page() recursion loop.
>
> Fixes: f165b378bbdf ("mm: uninitialized struct page poisoning sanity
> checking")
>
> Signed-off-by: Pavel Tatashin
> Acked-by: Michal Hocko
Thanks. I added a cc:stable to make sure this gets into 4.17.x.
Re: [PATCH v2] mm: teach dump_page() to correctly output poisoned struct pages
On Mon, 2 Jul 2018 14:05:36 -0400 Pavel Tatashin
wrote:
> If struct page is poisoned, and uninitialized access is detected via
> PF_POISONED_CHECK(page) dump_page() is called to output the page. But,
> the dump_page() itself accesses struct page to determine how to print
> it, and therefore gets into a recursive loop.
>
> For example:
> dump_page()
> __dump_page()
> PageSlab(page)
>PF_POISONED_CHECK(page)
> VM_BUG_ON_PGFLAGS(PagePoisoned(page), page)
> dump_page() recursion loop.
>
> Fixes: f165b378bbdf ("mm: uninitialized struct page poisoning sanity
> checking")
>
> Signed-off-by: Pavel Tatashin
> Acked-by: Michal Hocko
Thanks. I added a cc:stable to make sure this gets into 4.17.x.
Re: [PATCH v2] mm: teach dump_page() to correctly output poisoned struct pages
On Mon 02-07-18 14:05:36, Pavel Tatashin wrote:
[...]
> void __dump_page(struct page *page, const char *reason)
> {
> + bool page_poisoned = PagePoisoned(page);
> + int mapcount;
> +
> + /*
> + * If struct page is poisoned don't access Page*() functions as that
> + * leads to recursive loop. Page*() check for poisoned pages, and calls
> + * dump_page() when detected.
> + */
> + if (page_poisoned) {
> + pr_emerg("page:%px is uninitialized and poisoned", page);
> + goto hex_only;
> + }
Thanks for the updated comment. Exactly what I was looking for!
--
Michal Hocko
SUSE Labs
Re: [PATCH v2] mm: teach dump_page() to correctly output poisoned struct pages
On Mon 02-07-18 14:05:36, Pavel Tatashin wrote:
[...]
> void __dump_page(struct page *page, const char *reason)
> {
> + bool page_poisoned = PagePoisoned(page);
> + int mapcount;
> +
> + /*
> + * If struct page is poisoned don't access Page*() functions as that
> + * leads to recursive loop. Page*() check for poisoned pages, and calls
> + * dump_page() when detected.
> + */
> + if (page_poisoned) {
> + pr_emerg("page:%px is uninitialized and poisoned", page);
> + goto hex_only;
> + }
Thanks for the updated comment. Exactly what I was looking for!
--
Michal Hocko
SUSE Labs
