[PATCH] xenpm: sanitize allocations in show_cpufreq_para_by_cpuid()

[Jan Beulich]

malloc(), when passed zero size, may return NULL (the behavior is
implementation defined). Extend the ->gov_num check to the other two
allocations as well. Don't chance then actually using a NULL in
print_cpufreq_para().

Fixes: 75e06d089d48 ("xenpm: add cpu frequency control interface, through which 
user can")
Signed-off-by: Jan Beulich <jbeul...@suse.com>

--- a/tools/misc/xenpm.c
+++ b/tools/misc/xenpm.c
@@ -840,8 +840,9 @@ static void print_cpufreq_para(int cpuid
     }
     else
     {
-        printf("scaling_avail_gov    : %s\n",
-               p_cpufreq->scaling_available_governors);
+        if ( p_cpufreq->gov_num )
+            printf("scaling_avail_gov    : %s\n",
+                   p_cpufreq->scaling_available_governors);
 
         printf("current_governor     : %s\n", p_cpufreq->u.s.scaling_governor);
         if ( !strncmp(p_cpufreq->u.s.scaling_governor,
@@ -907,7 +908,8 @@ static int show_cpufreq_para_by_cpuid(xc
         p_cpufreq->scaling_available_frequencies = NULL;
         p_cpufreq->scaling_available_governors = NULL;
 
-        if (!(p_cpufreq->affected_cpus =
+        if (p_cpufreq->cpu_num &&
+            !(p_cpufreq->affected_cpus =
               malloc(p_cpufreq->cpu_num * sizeof(uint32_t))))
         {
             fprintf(stderr,
@@ -916,7 +918,8 @@ static int show_cpufreq_para_by_cpuid(xc
             ret = -ENOMEM;
             goto out;
         }
-        if (!(p_cpufreq->scaling_available_frequencies =
+        if (p_cpufreq->freq_num &&
+            !(p_cpufreq->scaling_available_frequencies =
               malloc(p_cpufreq->freq_num * sizeof(uint32_t))))
         {
             fprintf(stderr,