linux-kernel - [PATCH v2] of: fdt: Fix the len check in early_init_dt_check_for

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Message-ID: <20251105090004.83119-1-yuntao.wang@linux.dev>
Date: Wed,  5 Nov 2025 17:00:04 +0800
From: Yuntao Wang <yuntao.wang@...ux.dev>
To: geert@...ux-m68k.org,
	robh@...nel.org,
	saravanak@...gle.com
Cc: devicetree@...r.kernel.org,
	geert+renesas@...der.be,
	linux-kernel@...r.kernel.org,
	yuntao.wang@...ux.dev
Subject: [PATCH v2] of: fdt: Fix the len check in early_init_dt_check_for_elfcorehdr()

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

Comparing them directly is incorrect. Convert units before comparison.

Fixes: f7e7ce93aac1 ("of: fdt: Add generic support for handling elf core headers property")
Fixes: e62aaeac426ab1dd ("arm64: kdump: provide /proc/vmcore file")
Reviewed-by: Geert Uytterhoeven <geert+renesas@...der.be>
Signed-off-by: Yuntao Wang <yuntao.wang@...ux.dev>
---
v1 -> v2: Add a new Fixes tag as suggested by Geert Uytterhoeven

 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..f79461f5cffc 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -812,6 +812,7 @@ static void __init early_init_dt_check_for_initrd(unsigned long node)
  */
 static void __init early_init_dt_check_for_elfcorehdr(unsigned long node)
 {
+	int t_len = (dt_root_addr_cells + dt_root_size_cells) * sizeof(__be32);
 	const __be32 *prop;
 	int len;
 
@@ -821,7 +822,7 @@ static void __init early_init_dt_check_for_elfcorehdr(unsigned long node)
 	pr_debug("Looking for elfcorehdr property... ");
 
 	prop = of_get_flat_dt_prop(node, "linux,elfcorehdr", &len);
-	if (!prop || (len < (dt_root_addr_cells + dt_root_size_cells)))
+	if (!prop || len < t_len)
 		return;
 
 	elfcorehdr_addr = dt_mem_next_cell(dt_root_addr_cells, &prop);
-- 
2.51.0