fix race condition

NEWS

@@ -1,6 +1,7 @@
 procps-3.2.5 --> procps-3.2.6
 
 more MIPS crud  -- thanks Jim Gifford and Ryan Oliver
+begin prep for setuid
 
 procps-3.2.4 --> procps-3.2.5
 

proc/ksym.c

@@ -509,8 +509,10 @@ int open_psdb_message(const char *restrict override, void (*message)(const char
     ||
     (sm=getenv("PS_SYSTEM_MAP"))
   ){
+    if(!have_privs){
       read_and_parse();
       if(sysmap_mmap(sm, message)) return 0;
+    }
     /* failure is better than ignoring the user & using bad data */
     return -1;           /* ought to return "Namelist not found." */
   }

proc/library.map

@@ -1,7 +1,7 @@
 # for --version-script
 # WTF is the syntax for this file?
 # Give me a BNF, man!
-_3_2_4 {
+_3_2_5 {
 global:
   __cyg_profile_func_enter; __cyg_profile_func_exit; main;
 
@@ -10,7 +10,7 @@ global:
   openproc; closeproc;
   tty_to_dev; dev_to_tty; open_psdb_message; open_psdb; lookup_wchan;
   display_version; procps_version; linux_version_code;
-  Hertz; smp_num_cpus;
+  Hertz; smp_num_cpus; have_privs;
   sprint_uptime; uptime; user_from_uid; print_uptime; loadavg;
   pretty_print_signals; print_given_signals; unix_print_signals; signal_name_to_number; signal_number_to_name;
   meminfo; vminfo; getstat; getdiskstat; getpartitions_num; getslabinfo; get_pid_digits;

proc/sysinfo.c

@@ -170,8 +170,13 @@ static void old_Hertz_hack(void){
   }
 }
 
+// same as:   euid != uid || egid != gid
+#ifndef AT_SECURE
+#define AT_SECURE      23     // secure mode boolean (true if setuid, etc.)
+#endif
+
 #ifndef AT_CLKTCK
-#define AT_CLKTCK       17    /* frequency of times() */
+#define AT_CLKTCK       17    // frequency of times()
 #endif
 
 #define NOTE_NOT_FOUND 42
@@ -189,8 +194,21 @@ static unsigned long find_elf_note(unsigned long findme){
   return NOTE_NOT_FOUND;
 }
 
+int have_privs;
+
+static int check_for_privs(void){
+  unsigned long rc = find_elf_note(AT_SECURE);
+  if(rc==NOTE_NOT_FOUND){
+    // not valid to run this code after UID or GID change!
+    // (if needed, may use AT_UID and friends instead)
+    rc = geteuid() != getuid() || getegid() != getgid();
+  }
+  return !!rc;
+}
+
 static void init_libproc(void) __attribute__((constructor));
 static void init_libproc(void){
+  have_privs = check_for_privs();
   // ought to count CPUs in /proc/stat instead of relying
   // on glibc, which foolishly tries to parse /proc/cpuinfo
   //

proc/sysinfo.h

@@ -8,6 +8,7 @@ EXTERN_C_BEGIN
 
 extern unsigned long long Hertz;   /* clock tick frequency */
 extern long smp_num_cpus;     /* number of CPUs */
+extern int have_privs;     /* boolean, true if setuid or similar */
 
 #if 0
 #define JT double