From: smallem <sridhar.mallem@oracle.com>
Date: Thu, 4 Oct 2018 17:54:44 +0000 (-0400)
Subject: fix issue 2696 to dynamically allocate grname buffer in increments of _SC_GETGR_R_SIZ... 
X-Git-Url: https://git.verplant.org/?a=commitdiff_plain;h=436dacdb577300ad6ed4692c95089f22ae98de3c;p=collectd.git

fix issue 2696 to dynamically allocate grname buffer in increments of _SC_GETGR_R_SIZE_MAX/_SC_PAGESIZE
---

diff --git a/src/exec.c b/src/exec.c
index b145e813..2c99ce2a 100644
--- a/src/exec.c
+++ b/src/exec.c
@@ -39,6 +39,7 @@
 #include <signal.h>
 #include <sys/types.h>
 
+#include <stdlib.h>
 #ifdef HAVE_SYS_CAPABILITY_H
 #include <sys/capability.h>
 #endif
@@ -78,6 +79,11 @@ typedef struct program_list_and_notification_s {
 } program_list_and_notification_t;
 
 /*
+ * constants
+ */
+const long int MAX_GRBUF_SIZE = 65536;
+
+/*
  * Private variables
  */
 static program_list_t *pl_head;
@@ -408,21 +414,65 @@ static int fork_child(program_list_t *pl, int *fd_in, int *fd_out,
         grbuf_size = sysconf(_SC_PAGESIZE);
       if (grbuf_size <= 0)
         grbuf_size = 4096;
-      char grbuf[grbuf_size];
 
-      status = getgrnam_r(pl->group, &gr, grbuf, sizeof(grbuf), &gr_ptr);
-      if (status != 0) {
-        ERROR("exec plugin: Failed to get group information "
-              "for group ``%s'': %s",
-              pl->group, STRERROR(status));
-        goto failed;
+      long int size;
+      size = grbuf_size;
+      char *temp = NULL;
+      char *grbuf = NULL;
+      int getgr_failed = 0;
+      grbuf = malloc(size);
+      if (grbuf == NULL) {
+        ERROR("exec plugin: get group information for '%s' failed: buffer "
+              "malloc() failed",
+              pl->group);
+        getgr_failed = 1;
+        goto gr_finally;
+      }
+      int status;
+      while ((status = getgrnam_r(pl->group, &gr, grbuf, size, &gr_ptr)) != 0) {
+        switch (errno) {
+        case ERANGE:
+          if ((size + grbuf_size) < size ||
+              (size + grbuf_size) > MAX_GRBUF_SIZE) {
+            ERROR("exec plugin: get group information for '%s' max buffer "
+                  "limit (%ld) reached \n",
+                  pl->group, MAX_GRBUF_SIZE);
+            getgr_failed = 1;
+            goto gr_finally;
+          }
+          /* grow the buffer by 'grbuf_size' each time getgrnamr fails */
+          size += grbuf_size;
+          temp = realloc(grbuf, size);
+          if (temp == NULL) {
+            ERROR("exec plugin: get group information for '%s' realloc() "
+                  "buffer to (%ld) failed ",
+                  pl->group, size);
+            getgr_failed = 1;
+            goto gr_finally;
+          }
+          grbuf = temp;
+          break;
+        default:
+          ERROR("exec plugin: default errno: get group information for '%s' "
+                "failed : %s",
+                pl->group, sstrerror(status, errbuf, sizeof(errbuf)));
+          getgr_failed = 1;
+          goto gr_finally;
+        }
       }
       if (gr_ptr == NULL) {
         ERROR("exec plugin: No such group: `%s'", pl->group);
-        goto failed;
+        getgr_failed = 1;
+        goto gr_finally;
       }
-
       egid = gr.gr_gid;
+    gr_finally:
+      free(grbuf);
+      DEBUG("exec plugin: release grbuf memory ");
+      grbuf = NULL;
+      if (getgr_failed > 0) {
+        goto failed;
+      }
     } else {
       egid = gid;
     }