of: address: Fix empty resource handling in __of_address_resource_bou…

…nds()

"resource->end" needs to always be equal to "resource->start + size - 1".
The previous version of the function did not perform the "- 1" in case
of an empty resource.

Also make sure to allow an empty resource at address 0.

Reported-by: Basharath Hussain Khaja <basharath@couthit.com>
Closes: https://lore.kernel.org/lkml/20250108140414.13530-1-basharath@couthit.com/
Fixes: 1a52a09 ("of: address: Unify resource bounds overflow checking")
Cc: stable@vger.kernel.org
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Link: https://lore.kernel.org/r/20250120-of-address-overflow-v1-1-dd68dbf47bce@linutronix.de
Signed-off-by: Rob Herring (Arm) <robh@kernel.org>

drivers/of/address.c

@@ -185,17 +185,15 @@ static u64 of_bus_pci_map(__be32 *addr, const __be32 *range, int na, int ns,
 
 static int __of_address_resource_bounds(struct resource *r, u64 start, u64 size)
 {
-	u64 end = start;
-
 	if (overflows_type(start, r->start))
 		return -EOVERFLOW;
-	if (size && check_add_overflow(end, size - 1, &end))
-		return -EOVERFLOW;
-	if (overflows_type(end, r->end))
-		return -EOVERFLOW;
 
 	r->start = start;
-	r->end = end;
+
+	if (!size)
+		r->end = wrapping_sub(typeof(r->end), r->start, 1);
+	else if (size && check_add_overflow(r->start, size - 1, &r->end))
+		return -EOVERFLOW;
 
 	return 0;
 }