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mm/page_alloc: reject unreasonable folio/compound page sizes in alloc_contig_range_noprof()

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Let's reject them early, which in turn makes folio_alloc_gigantic() reject
them properly.

To avoid converting from order to nr_pages, let's just add MAX_FOLIO_ORDER
and calculate MAX_FOLIO_NR_PAGES based on that.

While at it, let's just make the order a "const unsigned order".

Link: https://lkml.kernel.org/r/20250901150359.867252-7-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Acked-by: SeongJae Park <sj@kernel.org>
Reviewed-by: Wei Yang <richard.weiyang@gmail.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
David Hildenbrand 2025-09-01 17:03:27 +02:00 • committed by Andrew Morton
parent 3b864c8f55
commit 0bf2edf041
2 changed files with 13 additions and 3 deletions
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6
include/linux/mm.h
View file

@ -2055,11 +2055,13 @@ static inline long folio_nr_pages(const struct folio *folio)
/* Only hugetlbfs can allocate folios larger than MAX_ORDER */
#ifdef CONFIG_ARCH_HAS_GIGANTIC_PAGE
#define MAX_FOLIO_NR_PAGES (1UL << PUD_ORDER)
#define MAX_FOLIO_ORDER PUD_ORDER
#else
#define MAX_FOLIO_NR_PAGES MAX_ORDER_NR_PAGES
#define MAX_FOLIO_ORDER MAX_PAGE_ORDER
#endif
#define MAX_FOLIO_NR_PAGES (1UL << MAX_FOLIO_ORDER)
/*
* compound_nr() returns the number of pages in this potentially compound
* page. compound_nr() can be called on a tail page, and is defined to

10
mm/page_alloc.c
View file

@ -6838,6 +6838,7 @@ static int __alloc_contig_verify_gfp_mask(gfp_t gfp_mask, gfp_t *gfp_cc_mask)
int alloc_contig_range_noprof(unsigned long start, unsigned long end,
acr_flags_t alloc_flags, gfp_t gfp_mask)
{
const unsigned int order = ilog2(end - start);
unsigned long outer_start, outer_end;
int ret = 0;
@ -6855,6 +6856,14 @@ int alloc_contig_range_noprof(unsigned long start, unsigned long end,
PB_ISOLATE_MODE_CMA_ALLOC :
PB_ISOLATE_MODE_OTHER;
/*
* In contrast to the buddy, we allow for orders here that exceed
* MAX_PAGE_ORDER, so we must manually make sure that we are not
* exceeding the maximum folio order.
*/
if (WARN_ON_ONCE((gfp_mask & __GFP_COMP) && order > MAX_FOLIO_ORDER))
return -EINVAL;
gfp_mask = current_gfp_context(gfp_mask);
if (__alloc_contig_verify_gfp_mask(gfp_mask, (gfp_t *)&cc.gfp_mask))
return -EINVAL;
@ -6952,7 +6961,6 @@ int alloc_contig_range_noprof(unsigned long start, unsigned long end,
free_contig_range(end, outer_end - end);
} else if (start == outer_start && end == outer_end && is_power_of_2(end - start)) {
struct page *head = pfn_to_page(start);
int order = ilog2(end - start);
check_new_pages(head, order);
prep_new_page(head, order, gfp_mask, 0);