Patch "mm, hwpoison: fixup "mm: check the return value of lookup_page_ext for all call sites"" has been added to the 4.4-stable tree

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;a=summary

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 <[email protected]> know about it.

Date: Fri, 24 Nov 2017 11:13:07 +0100
To: Greg KH <[email protected]>
From: Michal Hocko <[email protected]>
Subject: mm, hwpoison: fixup "mm: check the return value of lookup_page_ext for all call sites"

From: Michal Hocko <[email protected]>

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.

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

@@ -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 [email protected] are

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