Commit 0bf2edf0 authored by David Hildenbrand's avatar David Hildenbrand Committed by Andrew Morton
Browse files

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

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: default avatarDavid Hildenbrand <david@redhat.com>
Reviewed-by: default avatarZi Yan <ziy@nvidia.com>
Acked-by: default avatarSeongJae Park <sj@kernel.org>
Reviewed-by: default avatarWei Yang <richard.weiyang@gmail.com>
Reviewed-by: default avatarLorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: default avatarLiam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 3b864c8f

include/linux/mm.h

+4 −2
Original line number Diff line number Diff line
@@ -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

mm/page_alloc.c

+9 −1
Original line number Diff line number Diff line
@@ -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);