[rrd-developers] [PATCH] rrd_daemon: pay attention to the return value of realpath

[kernel-hacker at bennee.com]

From: Alex Bennee <ajb at cbnl.com>

When the realpath() change was introduced it failed to take account of the potential
for a failure of realpath if it can't navigate to the full path. As a result the strdup
would fail.

Unfortunatly this change broke rrdcached's automatic creation of it's journal path (although
in my case this is handled by packaging). However we still make the call to rrd_mkdir_p to
trap other cases like existing non-dirs. It also removes the strdup as realpath will allocate
a buffer for you if you ask.
---
 src/rrd_daemon.c |   40 ++++++++++++++++++++++------------------
 1 files changed, 22 insertions(+), 18 deletions(-)

diff --git a/src/rrd_daemon.c b/src/rrd_daemon.c
index 2209320..3811442 100644
--- a/src/rrd_daemon.c
+++ b/src/rrd_daemon.c
@@ -3278,24 +3278,28 @@ static int read_options (int argc, char **argv) /* {{{ */
 
       case 'j':
       {
-        char journal_dir_actual[PATH_MAX];
-        const char *dir;
-        dir = journal_dir = strdup(realpath((const char *)optarg, journal_dir_actual));
-
-        status = rrd_mkdir_p(dir, 0777);
-        if (status != 0)
-        {
-          fprintf(stderr, "Failed to create journal directory '%s': %s\n",
-              dir, rrd_strerror(errno));
-          return 6;
-        }
-
-        if (access(dir, R_OK|W_OK|X_OK) != 0)
-        {
-          fprintf(stderr, "Must specify a writable directory with -j! (%s)\n",
-                  errno ? rrd_strerror(errno) : "");
-          return 6;
-        }
+	journal_dir = realpath((const char *)optarg, NULL);
+	if (journal_dir)
+	{
+	  // a resolved realpath implies existing path, however rrd_mkdir_p also runs checks
+	  status = rrd_mkdir_p(realpath, 0777);
+	  if (status != 0)
+	  {
+	    fprintf(stderr, "Failed to create journal directory '%s': %s\n",
+		    realpath, rrd_strerror(errno));
+	    return 6;
+	  }
+	  if (access(realpath, R_OK|W_OK|X_OK) != 0)
+	  {
+	    fprintf(stderr, "Must specify a writable directory with -j! (%s)\n",
+		    errno ? rrd_strerror(errno) : "");
+	    return 6;
+	  }
+	} else {
+	  fprintf(stderr, "Unable to resolve journal path (%s,%s)\n", optarg,
+		  errno ? rrd_strerror(errno) : "");
+	  return 6;
+	}
       }
       break;
 
-- 
1.7.3.2