increase default buf size to 1024 and add protection code for changes of _SC_GETGR_R_...

Change-Id: I6abbe0da54442eb1172b0d611700b51d83c62e00

diff --git a/src/atrace/atrace.cpp b/src/atrace/atrace.cpp
index 12f005f30d329211b8215347bdc0c2288ffc32f5..fb2ec1f8b199385d21934b561f8a498fc7cf69a6 100755 (executable)
--- a/src/atrace/atrace.cpp
+++ b/src/atrace/atrace.cpp
@@ -43,6 +43,7 @@
 
 #define BACKUP_TRACE   "/tmp/trace.backup"
 #define BOOTUP_TRACE   "/etc/ttrace.conf"
+#define DEF_GR_SIZE    1024
 #else
 #include <binder/IBinder.h>
 #include <binder/IServiceManager.h>
@@ -507,11 +508,40 @@ static bool setTagsProperty(uint64_t tags)
 
 //atrace "--init_exec" mode
        if(g_init_exec) {
-               char buf[256];  //insufficient buffer size can cause "ERANGE" as a result of getgrnam_r
-                if(0 != getgrnam_r(TTRACE_GROUP_NAME, &group_dev, buf, sizeof(buf), &group_ptr))
+               size_t bufSize = DEF_GR_SIZE;
+               char buf[DEF_GR_SIZE];
+               int ret = 0;
+               ret = getgrnam_r(TTRACE_GROUP_NAME, &group_dev, buf, bufSize, &group_ptr);
+
+               if (ret != 0 && ret != ERANGE)
+               {
+                       fprintf(stderr, "Fail to group[%s] info: %s(%d)\n", TTRACE_GROUP_NAME, strerror_r(errno, str_error, sizeof(str_error)), errno);
+                       return false;
+               }
+               
+               bool isInvalid = false;
+               while(ret == ERANGE)
                {
-                   fprintf(stderr, "Fail to group[%s] info: %s(%d)\n", TTRACE_GROUP_NAME, strerror_r(errno, str_error, sizeof(str_error)), errno);
-                   return false;
+                       long int tmpSize = -1;
+
+                       if(!isInvalid)
+                               tmpSize = sysconf(_SC_GETGR_R_SIZE_MAX);
+
+                       if (tmpSize == -1) 
+                       {
+                               bufSize *= 2;
+                       }
+                       else bufSize = (size_t) tmpSize;
+
+                       char *dynbuf = (char *) malloc(bufSize);
+                       if(dynbuf == NULL)
+                       {
+                               fprintf(stderr, "Fail to allocate buffer for group[%s]: %s(%d)\n", TTRACE_GROUP_NAME, strerror_r(errno, str_error, sizeof(str_error)), errno);
+                               return false;
+                       }
+                       ret = getgrnam_r(TTRACE_GROUP_NAME, &group_dev, dynbuf, bufSize, &group_ptr);
+                       if(ret == ERANGE) isInvalid = true;
+                       free(dynbuf);
                }
 
                fd = open("/tmp/tmp_tag", O_CREAT | O_RDWR | O_CLOEXEC, 0666);