Re: [Linux-stable-mirror] [PATCH stable-4.4 1/2] mm: check the return value of lookup_page_ext for all call sites

On 11/22/2017, 01:09 PM, Michal Hocko wrote:

--- a/mm/debug-pagealloc.c +++ b/mm/debug-pagealloc.c @@ -34,6 +34,8 @@ static inline void set_page_poison(struct page *page) struct page_ext *page_ext; page_ext = lookup_page_ext(page);

• if (page_ext)

• return;
  

  __set_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);

} @@ -42,6 +44,8 @@ static inline void clear_page_poison(struct page *page) struct page_ext *page_ext; page_ext = lookup_page_ext(page);

• if (page_ext)

• return;
  

  __clear_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);

} @@ -50,6 +54,8 @@ static inline bool page_poison(struct page *page) struct page_ext *page_ext; page_ext = lookup_page_ext(page);

• if (page_ext)

• return false;
  

  return test_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);

Now I am confused, your SLE12-SP2's backport in patches.fixes/0001-mm-check-the-return-value-of-lookup_page_ext-for-all.patch does the opposite in all three: + if (!page_ext) + return;

thanks,