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Message-Id: <20231012011106.2425309-1-hyesoo.yu@samsung.com>
Date: Thu, 12 Oct 2023 10:11:06 +0900
From: Hyesoo Yu <hyesoo.yu@...sung.com>
To: unlisted-recipients:; (no To-header on input)
Cc: Hyesoo Yu <hyesoo.yu@...sung.com>,
Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org
Subject: [PATCH] mm: page_alloc: check the order of compound page event when
the order is 0
For compound pages, the head sets the PG_head flag and
the tail sets the compound_head to indicate the head page.
If a user allocates a compound page and frees it with a different
order, the compound page information will not be properly
initialized. To detect this problem, compound_page(page) and
the order are compared, but it is not checked when the order is 0.
That error should be checked regardless of the order.
Signed-off-by: Hyesoo Yu <hyesoo.yu@...sung.com>
---
mm/page_alloc.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 95546f376302..fc92ac93c7c8 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1078,6 +1078,7 @@ static __always_inline bool free_pages_prepare(struct page *page,
int bad = 0;
bool skip_kasan_poison = should_skip_kasan_poison(page, fpi_flags);
bool init = want_init_on_free();
+ bool compound = PageCompound(page);
VM_BUG_ON_PAGE(PageTail(page), page);
@@ -1096,16 +1097,15 @@ static __always_inline bool free_pages_prepare(struct page *page,
return false;
}
+ VM_BUG_ON_PAGE(compound && compound_order(page) != order, page);
+
/*
* Check tail pages before head page information is cleared to
* avoid checking PageCompound for order-0 pages.
*/
if (unlikely(order)) {
- bool compound = PageCompound(page);
int i;
- VM_BUG_ON_PAGE(compound && compound_order(page) != order, page);
-
if (compound)
page[1].flags &= ~PAGE_FLAGS_SECOND;
for (i = 1; i < (1 << order); i++) {
--
2.25.1
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