Fix an inappropriate free of a non-dynamic value. While here, make the

code more naive and robust:
1.  When setting ev_value, also always set ev_flags appropriately
2.  Always check ev_value and ev_flags before calling free.

Both the value and the EV_DYNAMIC property can come directly from the
consumers of the environment functionality, so it's good to be careful.
And since this code is typically not looked at for long periods of
time, it's good to have it be a little "dumb-looking".

Trigger case for the bug:
        env_setenv("foo", 0, "1", NULL, NULL);
        env_setenv("foo", 0, "2", NULL, NULL);

Obtained from:	Juniper Networks, Inc.

1 files changed, 12 insertions, 9 deletions

diff --git a/lib/libstand/environment.c b/lib/libstand/environment.c
index fde4cf9..291e330 100644
--- a/lib/libstand/environment.c
+++ b/lib/libstand/environment.c
@@ -75,7 +75,14 @@ env_setenv(const char *name, int flags, const void *value,
 	 * for one already.
 	 */
 	if ((ev->ev_sethook != NULL) && !(flags & EV_NOHOOK))
-	    return(ev->ev_sethook(ev, flags, value));
+	    return (ev->ev_sethook(ev, flags, value));
+
+	/* If there is data in the variable, discard it. */
+	if (ev->ev_value != NULL && (ev->ev_flags & EV_DYNAMIC) != 0)
+	    free(ev->ev_value);
+	ev->ev_value = NULL;
+	ev->ev_flags &= ~EV_DYNAMIC;
+
     } else {
 
 	/*
@@ -84,6 +91,7 @@ env_setenv(const char *name, int flags, const void *value,
 	ev = malloc(sizeof(struct env_var));
 	ev->ev_name = strdup(name);
 	ev->ev_value = NULL;
+	ev->ev_flags = 0;
 	/* hooks can only be set when the variable is instantiated */
 	ev->ev_sethook = sethook;
 	ev->ev_unsethook = unsethook;
@@ -117,21 +125,16 @@ env_setenv(const char *name, int flags, const void *value,
 	    }
 	}
     }
-    
-    /* If there is data in the variable, discard it */
-    if (ev->ev_value != NULL)
-	free(ev->ev_value);
 
     /* If we have a new value, use it */
     if (flags & EV_VOLATILE) {
 	ev->ev_value = strdup(value);
+	ev->ev_flags |= EV_DYNAMIC;
     } else {
 	ev->ev_value = (char *)value;
+	ev->ev_flags |= flags & EV_DYNAMIC;
     }
 
-    /* Keep the flag components that are relevant */
-    ev->ev_flags = flags & (EV_DYNAMIC);
-
     return(0);
 }
 
@@ -201,7 +204,7 @@ env_discard(struct env_var *ev)
     if (environ == ev)
 	environ = ev->ev_next;
     free(ev->ev_name);
-    if (ev->ev_flags & EV_DYNAMIC)
+    if (ev->ev_value != NULL && (ev->ev_flags & EV_DYNAMIC) != 0)
 	free(ev->ev_value);
     free(ev);
 }