linux-kernel - [PATCH] of: fdt: Fix the len check in early_init_dt_check_for_usable_mem

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Message-ID: <20251102141416.160192-1-yuntao.wang@linux.dev>
Date: Sun,  2 Nov 2025 22:14:16 +0800
From: Yuntao Wang <yuntao.wang@...ux.dev>
To: linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org
Cc: Rob Herring <robh@...nel.org>,
	Saravana Kannan <saravanak@...gle.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Baoquan He <bhe@...hat.com>,
	Zhen Lei <thunder.leizhen@...wei.com>,
	Chen Zhou <chenzhou10@...wei.com>,
	Yuntao Wang <yuntao.wang@...ux.dev>
Subject: [PATCH] of: fdt: Fix the len check in early_init_dt_check_for_usable_mem_range()

The len value is in bytes, while `dt_root_addr_cells + dt_root_size_cells`
is in cells (4 bytes per cell).

The modulo calculation between them is incorrect, the units must be
converted first.

Fixes: fb319e77a0e7 ("of: fdt: Add memory for devices by DT property "linux,usable-memory-range"")
Signed-off-by: Yuntao Wang <yuntao.wang@...ux.dev>
---
 drivers/of/fdt.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index 0edd639898a6..21ddc28a1257 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -852,6 +852,7 @@ void __init early_init_dt_check_for_usable_mem_range(void)
 	const __be32 *prop, *endp;
 	int len, i;
 	unsigned long node = chosen_node_offset;
+	int t_len = (dt_root_addr_cells + dt_root_size_cells) * sizeof(__be32);
 
 	if ((long)node < 0)
 		return;
@@ -859,7 +860,7 @@ void __init early_init_dt_check_for_usable_mem_range(void)
 	pr_debug("Looking for usable-memory-range property... ");
 
 	prop = of_get_flat_dt_prop(node, "linux,usable-memory-range", &len);
-	if (!prop || (len % (dt_root_addr_cells + dt_root_size_cells)))
+	if (!prop || len % t_len)
 		return;
 
 	endp = prop + (len / sizeof(__be32));
-- 
2.51.0