linux-kernel - [PATCH] x86/mtrr: Replace simple_strtoul with kstrtoul in parse_mtrr_spare

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Message-ID: <20251218101026.225019-1-thorsten.blum@linux.dev>
Date: Thu, 18 Dec 2025 11:10:23 +0100
From: Thorsten Blum <thorsten.blum@...ux.dev>
To: Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Huth <thuth@...hat.com>
Cc: Thorsten Blum <thorsten.blum@...ux.dev>,
	linux-kernel@...r.kernel.org
Subject: [PATCH] x86/mtrr: Replace simple_strtoul with kstrtoul in parse_mtrr_spare_reg

Replace simple_strtoul() with the recommended kstrtoul() for parsing the
'mtrr_spare_reg_nr' boot parameter.

Check the return value of kstrtoul() and reject invalid values. This
adds error handling while preserving behavior for existing values, and
removes use of the deprecated simple_strtoul() helper. The current code
silently sets 'nr_mtrr_spare_reg = 0' if parsing fails, instead of
leaving the default value (CONFIG_MTRR_SANITIZER_SPARE_REG_NR_DEFAULT)
unchanged.

Signed-off-by: Thorsten Blum <thorsten.blum@...ux.dev>
---
 arch/x86/kernel/cpu/mtrr/cleanup.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/mtrr/cleanup.c b/arch/x86/kernel/cpu/mtrr/cleanup.c
index 763534d77f59..1de5134b1916 100644
--- a/arch/x86/kernel/cpu/mtrr/cleanup.c
+++ b/arch/x86/kernel/cpu/mtrr/cleanup.c
@@ -437,9 +437,7 @@ static unsigned long nr_mtrr_spare_reg __initdata =
 
 static int __init parse_mtrr_spare_reg(char *arg)
 {
-	if (arg)
-		nr_mtrr_spare_reg = simple_strtoul(arg, NULL, 0);
-	return 0;
+	return kstrtoul(arg, 0, &nr_mtrr_spare_reg);
 }
 early_param("mtrr_spare_reg_nr", parse_mtrr_spare_reg);
 
-- 
Thorsten Blum <thorsten.blum@...ux.dev>
GPG: 1D60 735E 8AEF 3BE4 73B6  9D84 7336 78FD 8DFE EAD4