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@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20240718134755.378115-5-darwi@linutronix.de

diff --git a/tools/arch/x86/kcpuid/kcpuid.c b/tools/arch/x86/kcpuid/kcpuid.c
index a87cddc19554f738db5e074163f1c4192dc06c98..581d28c861eefd4e1d52df101dad350c2be05dfe 100644 (file)
--- 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;
@@ -206,12 +207,9 @@ static void raw_dump_range(struct cpuid_range *range)
 #define MAX_SUBLEAF_NUM                64
 struct cpuid_range *setup_cpuid_range(u32 input_eax)
 {
-       u32 max_func, idx_func;
-       int subleaf;
+       u32 max_func, idx_func, subleaf, max_subleaf;
+       u32 eax, ebx, ecx, edx, f = input_eax;
        struct cpuid_range *range;
-       u32 eax, ebx, ecx, edx;
-       u32 f = input_eax;
-       int max_subleaf;
        bool allzero;
 
        eax = input_eax;
@@ -256,7 +254,7 @@ 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;