linux-kernel - [PATCH v1 4/9] tools/x86/kcpuid: Protect against faulty "max subleaf" values

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Message-ID: <20240718134755.378115-5-darwi@linutronix.de>
Date: Thu, 18 Jul 2024 15:47:44 +0200
From: "Ahmed S. Darwish" <darwi@...utronix.de>
To: Borislav Petkov <bp@...en8.de>,
	Ingo Molnar <mingo@...hat.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	x86@...nel.org,
	x86-cpuid@...ts.linux.dev
Cc: Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org,
	"Ahmed S. Darwish" <darwi@...utronix.de>
Subject: [PATCH v1 4/9] tools/x86/kcpuid: Protect against faulty "max subleaf" values

Protect against the kcpuid code parsing faulty max subleaf numbers
through a min() expression.  Thus, ensuring that max_subleaf will always
be ≤ MAX_SUBLEAF_NUM.

Use "u32" for the subleaf numbers since kcpuid is compiled with -Wextra,
which includes signed/unsigned comparisons warnings.

Signed-off-by: Ahmed S. Darwish <darwi@...utronix.de>
---
 tools/arch/x86/kcpuid/kcpuid.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/tools/arch/x86/kcpuid/kcpuid.c b/tools/arch/x86/kcpuid/kcpuid.c
index a87cddc19554..c93015ee02e0 100644
--- a/tools/arch/x86/kcpuid/kcpuid.c
+++ b/tools/arch/x86/kcpuid/kcpuid.c
@@ -7,7 +7,8 @@
 #include <string.h>
 #include <getopt.h>
 
-#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
+#define ARRAY_SIZE(x)	(sizeof(x) / sizeof((x)[0]))
+#define min(a, b)	(((a) < (b)) ? (a) : (b))
 
 typedef unsigned int u32;
 typedef unsigned long long u64;
@@ -207,11 +208,10 @@ static void raw_dump_range(struct cpuid_range *range)
 struct cpuid_range *setup_cpuid_range(u32 input_eax)
 {
 	u32 max_func, idx_func;
-	int subleaf;
 	struct cpuid_range *range;
+	u32 subleaf, max_subleaf;
 	u32 eax, ebx, ecx, edx;
 	u32 f = input_eax;
-	int max_subleaf;
 	bool allzero;
 
 	eax = input_eax;
@@ -256,7 +256,7 @@ struct cpuid_range *setup_cpuid_range(u32 input_eax)
 		 * others have to be tried (0xf)
 		 */
 		if (f == 0x7 || f == 0x14 || f == 0x17 || f == 0x18)
-			max_subleaf = (eax & 0xff) + 1;
+			max_subleaf = min((eax & 0xff) + 1, max_subleaf);
 
 		if (f == 0xb)
 			max_subleaf = 2;
-- 
2.45.2