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Subject[PATCH mm v2] mm, kasan: fix for "integrate page_alloc init with HW_TAGS"
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My commit "integrate page_alloc init with HW_TAGS" changed the order of
kernel_unpoison_pages() and kernel_init_free_pages() calls. This leads
to complaints from the page unpoisoning code, as the poison pattern gets
overwritten for __GFP_ZERO allocations.

Fix by restoring the initial order. Also add a warning comment.

Reported-by: Vlastimil Babka <vbabka@suse.cz>
Reported-by: Sergei Trofimovich <slyfox@gentoo.org>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
mm/page_alloc.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 033bd92e8398..d2c020563c0b 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2328,6 +2328,13 @@ inline void post_alloc_hook(struct page *page, unsigned int order,
arch_alloc_page(page, order);
debug_pagealloc_map_pages(page, 1 << order);

+ /*
+ * Page unpoisoning must happen before memory initialization.
+ * Otherwise, the poison pattern will be overwritten for __GFP_ZERO
+ * allocations and the page unpoisoning code will complain.
+ */
+ kernel_unpoison_pages(page, 1 << order);
+
/*
* As memory initialization might be integrated into KASAN,
* kasan_alloc_pages and kernel_init_free_pages must be
@@ -2338,7 +2345,6 @@ inline void post_alloc_hook(struct page *page, unsigned int order,
if (init && !kasan_has_integrated_init())
kernel_init_free_pages(page, 1 << order);

- kernel_unpoison_pages(page, 1 << order);
set_page_owner(page, order, gfp_flags);
}

--
2.31.0.291.g576ba9dcdaf-goog
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