Re: [PATCH v7] mm: assert exclusive nid/zonenum bits at the page/folio access sites

["Hui Zhu" <hui.zhu@linux.dev>]

2026年6月26日 17:09, "David Hildenbrand (Arm)" <david@kernel.org mailto:david@kernel.org?to=%22David%20Hildenbrand%20(Arm)%22%20%3Cdavid%40kernel.org%3E > 写到:


> 
> > 
> > > 
> > > static inline enum zone_type folio_zonenum(const struct folio *folio)
> > >  {
> > >  +#if ZONES_WIDTH != 0
> > >  + ASSERT_EXCLUSIVE_BITS(folio->flags, ZONES_MASK << ZONES_PGSHIFT);
> > >  +#endif
> > >  return memdesc_zonenum(folio->flags);
> > >  }
> > > 
> >  
> >  Better to factor out a common macro alongside a comment for these two '#if'?
> > 
> Yes.
> 
> And while looking at it, doesn't memdesc_section have similar problems? And
> there are other callers of memdesc_zonenum we wouldn't handle. So the
> macro approach is only partially helpful I thing.
> 
> Maybe we should just pass by reference and fixup all callers? Ends up the cleanest.
> 

Hi David,

I think pass by reference is better than macro.

Would you like to send this out as a formal patch yourself?
Or would you prefer I include it in my next version with your
Signed-off-by?

Best,
Hui

> Untested:
> 
> From fb9b4e8c1d0419b960dc0cd4738d19d80d1fe14f Mon Sep 17 00:00:00 2001
> From: "David Hildenbrand (Arm)" <david@kernel.org>
> Date: Fri, 26 Jun 2026 11:06:39 +0200
> Subject: [PATCH] mm: fix KASAN memdec_flags checks for zone/node/section
> 
> Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
> ---
>  include/asm-generic/memory_model.h | 2 +-
>  include/linux/mm.h | 23 +++++++++++++++--------
>  include/linux/mm_inline.h | 4 ++--
>  include/linux/mmzone.h | 24 ++++++++++++------------
>  mm/page_alloc.c | 6 +++---
>  mm/slab.h | 2 +-
>  mm/sparse.c | 2 +-
>  7 files changed, 35 insertions(+), 28 deletions(-)
> 
> diff --git a/include/asm-generic/memory_model.h b/include/asm-generic/memory_model.h
> index efa6610acbc79..f8404bc7773c2 100644
> --- a/include/asm-generic/memory_model.h
> +++ b/include/asm-generic/memory_model.h
> @@ -53,7 +53,7 @@ static inline int pfn_valid(unsigned long pfn)
>  */
>  #define __page_to_pfn(pg) \
>  ({ const struct page *__pg = (pg); \
> - int __sec = memdesc_section(__pg->flags); \
> + int __sec = memdesc_section(&__pg->flags); \
>  (unsigned long)(__pg - __section_mem_map_addr(__nr_to_section(__sec))); \
>  })
>  
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 485df9c2dbddb..3111e4a6c9c4c 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -2286,22 +2286,28 @@ static inline int page_zone_id(struct page *page)
>  }
>  
>  #ifdef NODE_NOT_IN_PAGE_FLAGS
> -int memdesc_nid(memdesc_flags_t mdf);
> +int memdesc_nid(const memdesc_flags_t *mdf);
> +#elif defined(CONFIG_NUMA)
> +static inline int memdesc_nid(const memdesc_flags_t *mdf)
> +{
> + ASSERT_EXCLUSIVE_BITS(mdf->f, NODES_MASK << NODES_PGSHIFT);
> + return (mdf->f >> NODES_PGSHIFT) & NODES_MASK;
> +}
>  #else
> -static inline int memdesc_nid(memdesc_flags_t mdf)
> +static inline int memdesc_nid(const memdesc_flags_t *mdf)
>  {
> - return (mdf.f >> NODES_PGSHIFT) & NODES_MASK;
> + return 0;
>  }
>  #endif
>  
>  static inline int page_to_nid(const struct page *page)
>  {
> - return memdesc_nid(PF_POISONED_CHECK(page)->flags);
> + return memdesc_nid(&PF_POISONED_CHECK(page)->flags);
>  }
>  
>  static inline int folio_nid(const struct folio *folio)
>  {
> - return memdesc_nid(folio->flags);
> + return memdesc_nid(&folio->flags);
>  }
>  
>  #ifdef CONFIG_NUMA_BALANCING
> @@ -2541,12 +2547,13 @@ static inline void set_page_section(struct page *page, unsigned long section)
>  page->flags.f |= (section & SECTIONS_MASK) << SECTIONS_PGSHIFT;
>  }
>  
> -static inline unsigned long memdesc_section(memdesc_flags_t mdf)
> +static inline unsigned long memdesc_section(const memdesc_flags_t *mdf)
>  {
> - return (mdf.f >> SECTIONS_PGSHIFT) & SECTIONS_MASK;
> + ASSERT_EXCLUSIVE_BITS(mdf->f, SECTIONS_MASK << SECTIONS_PGSHIFT);
> + return (mdf->f >> SECTIONS_PGSHIFT) & SECTIONS_MASK;
>  }
>  #else /* !SECTION_IN_PAGE_FLAGS */
> -static inline unsigned long memdesc_section(memdesc_flags_t mdf)
> +static inline unsigned long memdesc_section(const memdesc_flags_t *mdf)
>  {
>  return 0;
>  }
> diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h
> index a8430a7ae0544..efcddb9925add 100644
> --- a/include/linux/mm_inline.h
> +++ b/include/linux/mm_inline.h
> @@ -650,7 +650,7 @@ static inline bool vma_has_recency(const struct vm_area_struct *vma)
>  static inline size_t num_pages_contiguous(struct page **pages, size_t nr_pages)
>  {
>  struct page *cur_page = pages[0];
> - unsigned long section = memdesc_section(cur_page->flags);
> + unsigned long section = memdesc_section(&cur_page->flags);
>  size_t i;
>  
>  for (i = 1; i < nr_pages; i++) {
> @@ -660,7 +660,7 @@ static inline size_t num_pages_contiguous(struct page **pages, size_t nr_pages)
>  * In unproblematic kernel configs, page_to_section() == 0 and
>  * the whole check will get optimized out.
>  */
> - if (memdesc_section(cur_page->flags) != section)
> + if (memdesc_section(&cur_page->flags) != section)
>  break;
>  }
>  
> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> index ca27121871475..19e709d7a13de 100644
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -1272,31 +1272,31 @@ static inline bool zone_is_empty(const struct zone *zone)
>  #define KASAN_TAG_MASK ((1UL << KASAN_TAG_WIDTH) - 1)
>  #define ZONEID_MASK ((1UL << ZONEID_SHIFT) - 1)
>  
> -static inline enum zone_type memdesc_zonenum(memdesc_flags_t flags)
> +static inline enum zone_type memdesc_zonenum(const memdesc_flags_t *flags)
>  {
> - ASSERT_EXCLUSIVE_BITS(flags.f, ZONES_MASK << ZONES_PGSHIFT);
> - return (flags.f >> ZONES_PGSHIFT) & ZONES_MASK;
> + ASSERT_EXCLUSIVE_BITS(flags->f, ZONES_MASK << ZONES_PGSHIFT);
> + return (flags->f >> ZONES_PGSHIFT) & ZONES_MASK;
>  }
>  
>  static inline enum zone_type page_zonenum(const struct page *page)
>  {
> - return memdesc_zonenum(page->flags);
> + return memdesc_zonenum(&page->flags);
>  }
>  
>  static inline enum zone_type folio_zonenum(const struct folio *folio)
>  {
> - return memdesc_zonenum(folio->flags);
> + return memdesc_zonenum(&folio->flags);
>  }
>  
>  #ifdef CONFIG_ZONE_DEVICE
> -static inline bool memdesc_is_zone_device(memdesc_flags_t mdf)
> +static inline bool memdesc_is_zone_device(const memdesc_flags_t *mdf)
>  {
>  return memdesc_zonenum(mdf) == ZONE_DEVICE;
>  }
>  
>  static inline struct dev_pagemap *page_pgmap(const struct page *page)
>  {
> - VM_WARN_ON_ONCE_PAGE(!memdesc_is_zone_device(page->flags), page);
> + VM_WARN_ON_ONCE_PAGE(!memdesc_is_zone_device(&page->flags), page);
>  return page_folio(page)->pgmap;
>  }
>  
> @@ -1311,9 +1311,9 @@ static inline struct dev_pagemap *page_pgmap(const struct page *page)
>  static inline bool zone_device_pages_have_same_pgmap(const struct page *a,
>  const struct page *b)
>  {
> - if (memdesc_is_zone_device(a->flags) != memdesc_is_zone_device(b->flags))
> + if (memdesc_is_zone_device(&a->flags) != memdesc_is_zone_device(&b->flags))
>  return false;
> - if (!memdesc_is_zone_device(a->flags))
> + if (!memdesc_is_zone_device(&a->flags))
>  return true;
>  return page_pgmap(a) == page_pgmap(b);
>  }
> @@ -1321,7 +1321,7 @@ static inline bool zone_device_pages_have_same_pgmap(const struct page *a,
>  extern void memmap_init_zone_device(struct zone *, unsigned long,
>  unsigned long, struct dev_pagemap *);
>  #else
> -static inline bool memdesc_is_zone_device(memdesc_flags_t mdf)
> +static inline bool memdesc_is_zone_device(const memdesc_flags_t *mdf)
>  {
>  return false;
>  }
> @@ -1338,12 +1338,12 @@ static inline struct dev_pagemap *page_pgmap(const struct page *page)
>  
>  static inline bool is_zone_device_page(const struct page *page)
>  {
> - return memdesc_is_zone_device(page->flags);
> + return memdesc_is_zone_device(&page->flags);
>  }
>  
>  static inline bool folio_is_zone_device(const struct folio *folio)
>  {
> - return memdesc_is_zone_device(folio->flags);
> + return memdesc_is_zone_device(&folio->flags);
>  }
>  
>  static inline bool is_zone_movable_page(const struct page *page)
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index ee902a468c2f5..020a97ca018e9 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -6904,15 +6904,15 @@ static void __free_contig_range_common(unsigned long pfn, unsigned long nr_pages
>  continue;
>  }
>  
> - if (start && memdesc_section(page->flags) != start_sec) {
> + if (start && memdesc_section(&page->flags) != start_sec) {
>  free_prepared_contig_range(start, i - nr_start);
>  start = page;
>  nr_start = i;
> - start_sec = memdesc_section(page->flags);
> + start_sec = memdesc_section(&page->flags);
>  } else if (!start) {
>  start = page;
>  nr_start = i;
> - start_sec = memdesc_section(page->flags);
> + start_sec = memdesc_section(&page->flags);
>  }
>  }
>  
> diff --git a/mm/slab.h b/mm/slab.h
> index bf2f87acf5e3a..1ae8e6084ba32 100644
> --- a/mm/slab.h
> +++ b/mm/slab.h
> @@ -155,7 +155,7 @@ static inline void *slab_address(const struct slab *slab)
>  
>  static inline int slab_nid(const struct slab *slab)
>  {
> - return memdesc_nid(slab->flags);
> + return memdesc_nid(&slab->flags);
>  }
>  
>  static inline pg_data_t *slab_pgdat(const struct slab *slab)
> diff --git a/mm/sparse.c b/mm/sparse.c
> index 16ac6df3c89fa..8e38477645131 100644
> --- a/mm/sparse.c
> +++ b/mm/sparse.c
> @@ -43,7 +43,7 @@ static u8 section_to_node_table[NR_MEM_SECTIONS] __cacheline_aligned;
>  static u16 section_to_node_table[NR_MEM_SECTIONS] __cacheline_aligned;
>  #endif
>  
> -int memdesc_nid(memdesc_flags_t mdf)
> +int memdesc_nid(const memdesc_flags_t *mdf)
>  {
>  return section_to_node_table[memdesc_section(mdf)];
>  }
> -- 
> 2.43.0
> 
> -- 
> Cheers,
> 
> David
>