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

[Wandun Chen <chenwandun1@gmail.com>]

From: Wandun Chen <chenwandun@lixiang.com>

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@lixiang.com>
Link: https://sashiko.dev/#/message/20260814084718.29C341F000E9%40smtp.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)
 {
-- 
2.43.0