This is a note to let you know that I've just added the patch titled

mm, hwpoison: fixup "mm: check the return value of lookup_page_ext for all call sites"

to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: mm-hwpoison-fixup-mm-check-the-return-value-of-lookup_page_ext-for-all-call-sites.patch and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From foo@baz Fri Nov 24 11:13:07 CET 2017

Date: Fri, 24 Nov 2017 11:13:07 +0100 To: Greg KH gregkh@linuxfoundation.org From: Michal Hocko mhocko@suse.com Subject: mm, hwpoison: fixup "mm: check the return value of lookup_page_ext for all call sites"

From: Michal Hocko mhocko@suse.com

Backport of the upstream commit f86e4271978b ("mm: check the return value of lookup_page_ext for all call sites") is wrong for hwpoison pages. I have accidentally negated the condition for bailout. This basically disables hwpoison pages tracking while the code still might crash on unusual configurations when struct pages do not have page_ext allocated. The fix is trivial to invert the condition.

Reported-by: Jiri Slaby jslaby@suse.cz Signed-off-by: Michal Hocko mhocko@suse.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- mm/debug-pagealloc.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/mm/debug-pagealloc.c +++ b/mm/debug-pagealloc.c @@ -34,7 +34,7 @@ static inline void set_page_poison(struc struct page_ext *page_ext;

page_ext = lookup_page_ext(page); - if (page_ext) + if (!page_ext) return; __set_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags); } @@ -44,7 +44,7 @@ static inline void clear_page_poison(str struct page_ext *page_ext;

page_ext = lookup_page_ext(page); - if (page_ext) + if (!page_ext) return; __clear_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags); } @@ -54,7 +54,7 @@ static inline bool page_poison(struct pa struct page_ext *page_ext;

page_ext = lookup_page_ext(page); - if (page_ext) + if (!page_ext) return false; return test_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags); }

Patches currently in stable-queue which might be from gregkh@linuxfoundation.org are

queue-4.4/mm-hwpoison-fixup-mm-check-the-return-value-of-lookup_page_ext-for-all-call-sites.patch