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mm: page_alloc: check the order of compound page even when the order is zero

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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>
This commit is contained in:
Hyesoo Yu 2023-10-23 17:32:16 +09:00 committed by Andrew Morton
parent be16dd764a
commit 76f26535d1
1 changed files with 3 additions and 3 deletions
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6
mm/page_alloc.c
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@ -1079,6 +1079,7 @@ 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);
@ -1097,16 +1098,15 @@ 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++) {