From 908b8ca0b3bf2af143a19d94814c1882b9165b8c Mon Sep 17 00:00:00 2001
From: Roman D <me@iamroman.org>
Date: Mon, 21 Aug 2023 22:24:13 +0200
Subject: [PATCH] Limit configurable CPU count to the number of detected CPU
 cores.

---
 client/src/proxmark3.c | 5 +++--
 client/src/util.c      | 6 +++++-
 client/src/util.h      | 3 ++-
 3 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/client/src/proxmark3.c b/client/src/proxmark3.c
index 26f4a5698..3e924a1c7 100644
--- a/client/src/proxmark3.c
+++ b/client/src/proxmark3.c
@@ -1004,8 +1004,9 @@ int main(int argc, char *argv[]) {
                 return 1;
             }
             long int ncpus = strtol(argv[i + 1], NULL, 10);
-            if (ncpus < 0 || ncpus >= INT_MAX) {
-                PrintAndLogEx(ERR, _RED_("ERROR:") " invalid number of CPU cores: --ncpu " _YELLOW_("%s") "\n", argv[i + 1]);
+            const int detected_cpus = detect_num_CPUs();
+            if (ncpus < 0 || ncpus >= detected_cpus) {
+                PrintAndLogEx(ERR, _RED_("ERROR:") " invalid number of CPU cores: --ncpu " _YELLOW_("%s") " (available: %d)\n", argv[i + 1], detected_cpus);
                 return 1;
             }
             g_numCPUs = ncpus;
diff --git a/client/src/util.c b/client/src/util.c
index 150b042a5..f1e58abe0 100644
--- a/client/src/util.c
+++ b/client/src/util.c
@@ -1079,12 +1079,16 @@ uint64_t HornerScheme(uint64_t num, uint64_t divider, uint64_t factor) {
     return result;
 }
 
-// determine number of logical CPU cores (use for multithreaded functions)
 int num_CPUs(void) {
     if (g_numCPUs > 0) {
         return g_numCPUs;
     }
 
+    return detect_num_CPUs();
+}
+
+// determine number of logical CPU cores (use for multithreaded functions)
+int detect_num_CPUs(void) {
 #if defined(_WIN32)
 #include <sysinfoapi.h>
     SYSTEM_INFO sysinfo;
diff --git a/client/src/util.h b/client/src/util.h
index 0712d8d18..fa636ce9b 100644
--- a/client/src/util.h
+++ b/client/src/util.h
@@ -131,7 +131,8 @@ void wiegand_add_parity_swapped(uint8_t *target, uint8_t *source, uint8_t length
 uint32_t PackBits(uint8_t start, uint8_t len, const uint8_t *bits);
 uint64_t HornerScheme(uint64_t num, uint64_t divider, uint64_t factor);
 
-int num_CPUs(void); // number of logical CPUs
+int num_CPUs(void);
+int detect_num_CPUs(void); // number of logical CPUs
 
 void str_lower(char *s); // converts string to lower case
 void str_upper(char *s); // converts string to UPPER case