This is a note to let you know that I've just added the patch titled
mm/page_alloc: correct start page when guard page debug is enabled
to the 5.15-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-page_alloc-correct-start-page-when-guard-page-debug-is-enabled.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 61e21cf2d2c3cc5e60e8d0a62a77e250fccda62c Mon Sep 17 00:00:00 2001
From: Kemeng Shi <shikemeng@xxxxxxxxxxxxxxx>
Date: Wed, 27 Sep 2023 17:44:01 +0800
Subject: mm/page_alloc: correct start page when guard page debug is enabled
From: Kemeng Shi <shikemeng@xxxxxxxxxxxxxxx>
commit 61e21cf2d2c3cc5e60e8d0a62a77e250fccda62c upstream.
When guard page debug is enabled and set_page_guard returns success, we
miss to forward page to point to start of next split range and we will do
split unexpectedly in page range without target page. Move start page
update before set_page_guard to fix this.
As we split to wrong target page, then splited pages are not able to merge
back to original order when target page is put back and splited pages
except target page is not usable. To be specific:
Consider target page is the third page in buddy page with order 2.
| buddy-2 | Page | Target | Page |
After break down to target page, we will only set first page to Guard
because of bug.
| Guard | Page | Target | Page |
When we try put_page_back_buddy with target page, the buddy page of target
if neither guard nor buddy, Then it's not able to construct original page
with order 2
| Guard | Page | buddy-0 | Page |
All pages except target page is not in free list and is not usable.
Link: https://lkml.kernel.org/r/20230927094401.68205-1-shikemeng@xxxxxxxxxxxxxxx
Fixes: 06be6ff3d2ec ("mm,hwpoison: rework soft offline for free pages")
Signed-off-by: Kemeng Shi <shikemeng@xxxxxxxxxxxxxxx>
Acked-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
mm/page_alloc.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -9481,6 +9481,7 @@ static void break_down_buddy_pages(struc
next_page = page;
current_buddy = page + size;
}
+ page = next_page;
if (set_page_guard(zone, current_buddy, high, migratetype))
continue;
@@ -9488,7 +9489,6 @@ static void break_down_buddy_pages(struc
if (current_buddy != target) {
add_to_free_list(current_buddy, zone, high, migratetype);
set_buddy_order(current_buddy, high);
- page = next_page;
}
}
}
Patches currently in stable-queue which might be from shikemeng@xxxxxxxxxxxxxxx are
queue-5.15/mm-page_alloc-correct-start-page-when-guard-page-debug-is-enabled.patch
