Re: [PATCH v2 2/5] of: reserved_mem: reject static regions overlapping no-map memory

[Marek Szyprowski]

On 18.08.2026 11:24, Wandun Chen wrote:
> From: Wandun Chen <chenwandun@xxxxxxxxxxx>
>
> Static no-map reserved-memory regions are marked in memblock.memory rather
> than memblock.reserved. So the reservation overlap check does not reject
> a static region that overlaps existing no-map memory.
>
> Both regions can then be initialized and hand the same physical memory to
> different reserved-memory drivers. So reject a static region that overlaps
> existing no-map memory.
>
> Sashiko found this issue in [1].
>
> Fixes: 86588296acbf ("fdt: Properly handle "no-map" field in the memory region")
> Signed-off-by: Wandun Chen <chenwandun@xxxxxxxxxxx>
Acked-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
> Link: https://protect2.fireeye.com/v1/url?k=c110879a-a8abef28-c1110cd5-905a08a8515a-5165b48469b02786&q=1&e=6166144c-5cef-48c6-9f6f-b36a72f258ac&u=https%3A%2F%2Fsashiko.dev%2F%23%2Fmessage%2F20260814084718.29C341F000E9%2540smtp.kernel.org [1]
> ---
>  drivers/of/of_reserved_mem.c |  3 ++-
>  include/linux/memblock.h     |  1 +
>  mm/memblock.c                | 14 ++++++++++++++
>  3 files changed, 17 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/of/of_reserved_mem.c b/drivers/of/of_reserved_mem.c
> index c6e73d710ee1..9fb2e4c29443 100644
> --- a/drivers/of/of_reserved_mem.c
> +++ b/drivers/of/of_reserved_mem.c
> @@ -152,7 +152,8 @@ static int __init early_init_dt_reserve_memory(phys_addr_t base,
>  		 * if the region isn't memory as it won't be mapped.
>  		 */
>  		if (memblock_overlaps_region(&memblock.memory, base, size) &&
> -		    memblock_is_region_reserved(base, size))
> +		    (memblock_is_region_reserved(base, size) ||
> +		     memblock_overlaps_nomap(base, size)))
>  			return -EBUSY;
>  
>  		return memblock_mark_nomap(base, size);
> diff --git a/include/linux/memblock.h b/include/linux/memblock.h
> index d62db9e776cf..27d68fbb3157 100644
> --- a/include/linux/memblock.h
> +++ b/include/linux/memblock.h
> @@ -148,6 +148,7 @@ int memblock_physmem_add(phys_addr_t base, phys_addr_t size);
>  void memblock_trim_memory(phys_addr_t align);
>  unsigned long memblock_addrs_overlap(phys_addr_t base1, phys_addr_t size1,
>  				     phys_addr_t base2, phys_addr_t size2);
> +bool memblock_overlaps_nomap(phys_addr_t base, phys_addr_t size);
>  bool memblock_overlaps_region(struct memblock_type *type,
>  			      phys_addr_t base, phys_addr_t size);
>  bool memblock_validate_numa_coverage(unsigned long threshold_bytes);
> diff --git a/mm/memblock.c b/mm/memblock.c
> index 9ce86349a29f..4cabfe365ac4 100644
> --- a/mm/memblock.c
> +++ b/mm/memblock.c
> @@ -202,6 +202,20 @@ memblock_addrs_overlap(phys_addr_t base1, phys_addr_t size1, phys_addr_t base2,
>  	return ((base1 < (base2 + size2)) && (base2 < (base1 + size1)));
>  }
>  
> +bool __init memblock_overlaps_nomap(phys_addr_t base, phys_addr_t size)
> +{
> +	struct memblock_region *region;
> +
> +	memblock_cap_size(base, &size);
> +	for_each_mem_region(region) {
> +		if (memblock_is_nomap(region) &&
> +		    memblock_addrs_overlap(base, size, region->base, region->size))
> +			return true;
> +	}
> +
> +	return false;
> +}
> +
>  bool __init_memblock memblock_overlaps_region(struct memblock_type *type,
>  					phys_addr_t base, phys_addr_t size)
>  {

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland