XUtils: check for multiplication overflow in allocation size

XUtils.c

@@ -13,6 +13,7 @@ in the source distribution for its full text.
 #include <errno.h>
 #include <fcntl.h>
 #include <stdarg.h>
+#include <stdint.h>
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
@@ -36,9 +37,21 @@ void* xMalloc(size_t size) {
    return data;
 }
 
+void* xMallocArray(size_t nmemb, size_t size) {
+   assert(nmemb > 0);
+   assert(size > 0);
+   if (SIZE_MAX / nmemb < size) {
+      fail();
+   }
+   return xMalloc(nmemb * size);
+}
+
 void* xCalloc(size_t nmemb, size_t size) {
    assert(nmemb > 0);
    assert(size > 0);
+   if (SIZE_MAX / nmemb < size) {
+      fail();
+   }
    void* data = calloc(nmemb, size);
    if (!data) {
       fail();
@@ -56,6 +69,15 @@ void* xRealloc(void* ptr, size_t size) {
    return data;
 }
 
+void* xReallocArray(void* ptr, size_t nmemb, size_t size) {
+   assert(nmemb > 0);
+   assert(size > 0);
+   if (SIZE_MAX / nmemb < size) {
+      fail();
+   }
+   return xRealloc(ptr, nmemb * size);
+}
+
 char* String_cat(const char* s1, const char* s2) {
    const size_t l1 = strlen(s1);
    const size_t l2 = strlen(s2);

XUtils.h

@@ -23,10 +23,14 @@ void fail(void) ATTR_NORETURN;
 
 void* xMalloc(size_t size);
 
+void* xMallocArray(size_t nmemb, size_t size);
+
 void* xCalloc(size_t nmemb, size_t size);
 
 void* xRealloc(void* ptr, size_t size);
 
+void* xReallocArray(void* ptr, size_t nmemb, size_t size);
+
 /*
  * String_startsWith gives better performance if strlen(match) can be computed
  * at compile time (e.g. when they are immutable string literals). :)

linux/LinuxProcessList.c

@@ -102,7 +102,7 @@ static void LinuxProcessList_initTtyDrivers(LinuxProcessList* this) {
 
    int numDrivers = 0;
    int allocd = 10;
-   ttyDrivers = xMalloc(sizeof(TtyDriver) * allocd);
+   ttyDrivers = xMallocArray(allocd, sizeof(TtyDriver));
    char* at = buf;
    while (*at != '\0') {
       at = strchr(at, ' ');    // skip first token
@@ -136,7 +136,7 @@ static void LinuxProcessList_initTtyDrivers(LinuxProcessList* this) {
       numDrivers++;
       if (numDrivers == allocd) {
          allocd += 10;
-         ttyDrivers = xRealloc(ttyDrivers, sizeof(TtyDriver) * allocd);
+         ttyDrivers = xReallocArray(ttyDrivers, allocd, sizeof(TtyDriver));
       }
    }
    numDrivers++;