[PATCH 02/11] of: reserved_mem: reject reserved memory outside physical address range

[Chen Wandun]

early_init_dt_reserve_memory() does not validate whether the region
falls within physical memory. If a device tree incorrectly specifies a
reserved memory region outside the physical address range:

 - For the non-nomap path, memblock_reserve() blindly adds the region
   to memblock.reserved, creating a stale entry that refers to
   non-existent memory.

 - For the nomap path, memblock_mark_nomap() silently fails to match
   any region in memblock.memory, but still returns success.

Add a memblock_overlaps_region() check at the entry of
early_init_dt_reserve_memory() to reject such regions before any
memblock operation takes place. This also simplifies the existing nomap
guard: the original "overlaps && is_reserved" condition reduces to just
"is_reserved", since the overlap with physical memory is already
guaranteed by the new check.

Signed-off-by: Chen Wandun <chenwandun at lixiang.com>
Tested-by: Zhao Meijing <zhaomeijing at lixiang.com>
---
 drivers/of/of_reserved_mem.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/drivers/of/of_reserved_mem.c b/drivers/of/of_reserved_mem.c
index 9d1b0193864c..03c676052dab 100644
--- a/drivers/of/of_reserved_mem.c
+++ b/drivers/of/of_reserved_mem.c
@@ -112,14 +112,21 @@ static int fdt_fixup_reserved_mem_node(unsigned long node,
 static int __init early_init_dt_reserve_memory(phys_addr_t base,
 					       phys_addr_t size, bool nomap)
 {
+	if (!memblock_overlaps_region(&memblock.memory, base, size)) {
+		phys_addr_t end = base + size - 1;
+
+		pr_warn("Reserved memory region %pa..%pa is outside of physical memory\n",
+			&base, &end);
+		return -EINVAL;
+	}
+
 	if (nomap) {
 		/*
 		 * If the memory is already reserved (by another region), we
-		 * should not allow it to be marked nomap, but don't worry
-		 * if the region isn't memory as it won't be mapped.
+		 * should not allow it to be marked nomap. The region being
+		 * physical memory is guaranteed by the overlap check above.
 		 */
-		if (memblock_overlaps_region(&memblock.memory, base, size) &&
-		    memblock_is_region_reserved(base, size))
+		if (memblock_is_region_reserved(base, size))
 			return -EBUSY;
 
 		return memblock_mark_nomap(base, size);
-- 
2.43.0