Re: [PATCH v1 06/36] mm/page_alloc: reject unreasonable folio/compound page sizes in alloc_contig_range_noprof()
From: Lorenzo Stoakes <hidden>
Date: 2025-08-28 14:38:33
Also in:
dri-devel, intel-gfx, io-uring, kvm, linux-crypto, linux-ide, linux-iommu, linux-kselftest, linux-mips, linux-mm, linux-mmc, linux-riscv, linux-s390, linux-scsi, lkml, netdev, virtualization
On Thu, Aug 28, 2025 at 12:01:10AM +0200, David Hildenbrand wrote:
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. Reviewed-by: Zi Yan <ziy@nvidia.com> Acked-by: SeongJae Park <sj@kernel.org> Signed-off-by: David Hildenbrand <redacted>
Some nits, but overall LGTM so: Reviewed-by: Lorenzo Stoakes <redacted>
quoted hunk ↗ jump to hunk
--- include/linux/mm.h | 6 ++++-- mm/page_alloc.c | 5 ++++- 2 files changed, 8 insertions(+), 3 deletions(-)diff --git a/include/linux/mm.h b/include/linux/mm.h index 00c8a54127d37..77737cbf2216a 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h@@ -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)
BIT()?
quoted hunk ↗ jump to hunk
+ /* * compound_nr() returns the number of pages in this potentially compound * page. compound_nr() can be called on a tail page, and is defined todiff --git a/mm/page_alloc.c b/mm/page_alloc.c index baead29b3e67b..426bc404b80cc 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c@@ -6833,6 +6833,7 @@ 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;@@ -6850,6 +6851,9 @@ int alloc_contig_range_noprof(unsigned long start, unsigned long end, PB_ISOLATE_MODE_CMA_ALLOC : PB_ISOLATE_MODE_OTHER; + if (WARN_ON_ONCE((gfp_mask & __GFP_COMP) && order > MAX_FOLIO_ORDER)) + return -EINVAL;
Possibly not worth it for a one off, but be nice to have this as a helper function, like:
static bool is_valid_order(gfp_t gfp_mask, unsigned int order)
{
return !(gfp_mask & __GFP_COMP) || order <= MAX_FOLIO_ORDER;
}
Then makes this:
if (WARN_ON_ONCE(!is_valid_order(gfp_mask, order)))
return -EINVAL;
Kinda self-documenting!
quoted hunk ↗ jump to hunk
+ gfp_mask = current_gfp_context(gfp_mask); if (__alloc_contig_verify_gfp_mask(gfp_mask, (gfp_t *)&cc.gfp_mask)) return -EINVAL;@@ -6947,7 +6951,6 @@ 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); --2.50.1