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@xxxxxxxxxxx>
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@xxxxxxxxxxx
Signed-off-by: Hyesoo Yu <hyesoo.yu@xxxxxxxxxxx>
Reviewed-by: Vishal Moola (Oracle) <vishal.moola@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
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@xxxxxxxxxxx are
mm-page_alloc-check-the-order-of-compound-page-even-when-the-order-is-zero.patch
