+ mm-page_alloc-check-the-order-of-compound-page-even-when-the-order-is-zero.patch added to mm-unstable branch

+ mm-page_alloc-check-the-order-of-compound-page-even-when-the-order-is-zero.patch added to mm-unstable branch

[Andrew Morton]

The patch titled
     Subject: mm: page_alloc: check the order of compound page even when the order is zero
has been added to the -mm mm-unstable branch.  Its filename is
     mm-page_alloc-check-the-order-of-compound-page-even-when-the-order-is-zero.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-page_alloc-check-the-order-of-compound-page-even-when-the-order-is-zero.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Hyesoo Yu <hyesoo.yu@samsung.com>
Subject: mm: page_alloc: check the order of compound page even when the order is zero
Date: Mon, 23 Oct 2023 17:32:16 +0900

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_order(page) and the order argument are compared, but this is not
checked when the order argument is zero.  That error should be checked
regardless of the order.

Link: https://lkml.kernel.org/r/20231023083217.1866451-1-hyesoo.yu@samsung.com
Signed-off-by: Hyesoo Yu <hyesoo.yu@samsung.com>
Reviewed-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

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

--- a/mm/page_alloc.c~mm-page_alloc-check-the-order-of-compound-page-even-when-the-order-is-zero
+++ a/mm/page_alloc.c
@@ -1079,6 +1079,7 @@ static __always_inline bool free_pages_p
 	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);
 
@@ -1097,16 +1098,15 @@ static __always_inline bool free_pages_p
 		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++) {
_

Patches currently in -mm which might be from hyesoo.yu@samsung.com are

mm-page_alloc-check-the-order-of-compound-page-even-when-the-order-is-zero.patch