From: David Herrmann <dh.herrmann@gmail.com>
Date: Wed, 31 Dec 2014 15:28:48 +0000 (+0100)
Subject: lldp: fix sd_lldp_save()
X-Git-Tag: v219~732
X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=elogind.git;a=commitdiff_plain;h=ee14ebf211df1322c3d8b550b931bbfa6cb3b033

lldp: fix sd_lldp_save()

Fix a bunch of needless memzero() calls, a bunch of use-after-free
regarding _cleanup_free_ and drop unused variables.

Hint: Do NOT use _cleanup_free_ for temporary strappend() helpers that are
freed multiple times. All you safe is the last free() call, which is
really not worth the trouble resetting it to NULL all the time.
---

diff --git a/src/libsystemd-network/sd-lldp.c b/src/libsystemd-network/sd-lldp.c
index 74ea810c8..fa4531005 100644
--- a/src/libsystemd-network/sd-lldp.c
+++ b/src/libsystemd-network/sd-lldp.c
@@ -429,7 +429,6 @@ static void lldp_mib_objects_flush(sd_lldp *lldp) {
 }
 
 int sd_lldp_save(sd_lldp *lldp, const char *lldp_file) {
-        _cleanup_free_ char *s = NULL, *t = NULL, *k = NULL;
         _cleanup_free_ char *temp_path = NULL;
         _cleanup_fclose_ FILE *f = NULL;
         uint8_t *mac, *port_id, type;
@@ -452,13 +451,13 @@ int sd_lldp_save(sd_lldp *lldp, const char *lldp_file) {
 
         HASHMAP_FOREACH(c, lldp->neighbour_mib, i) {
                 LIST_FOREACH(port, p, c->ports) {
+                        _cleanup_free_ char *s = NULL;
+                        char *k, *t;
 
                         r = lldp_read_chassis_id(p->packet, &type, &length, &mac);
                         if (r < 0)
                                 continue;
 
-                        memzero(buf, LINE_MAX);
-
                         sprintf(buf, "'_Chassis=%02x:%02x:%02x:%02x:%02x:%02x' '_CType=%d' ",
                                 mac[0], mac[1], mac[2], mac[3], mac[4], mac[5], type);
 
@@ -467,57 +466,43 @@ int sd_lldp_save(sd_lldp *lldp, const char *lldp_file) {
                                 return -ENOMEM;
 
                         r = lldp_read_port_id(p->packet, &type, &length, &port_id);
-                        if (r < 0) {
-                                free(s);
+                        if (r < 0)
                                 continue;
-                        }
 
-                        memzero(buf, LINE_MAX);
                         if (type != LLDP_PORT_SUBTYPE_MAC_ADDRESS) {
-
                                 k = strndup((char *) port_id, length -1);
                                 if (!k)
                                         return -ENOMEM;
 
                                 sprintf(buf, "'_Port=%s' '_PType=%d' ", k , type);
-
-                                t = strappend(s, buf);
-
                                 free(k);
-                                k = NULL;
                         } else {
-
                                 mac = port_id;
-
                                 sprintf(buf, "'_Port=%02x:%02x:%02x:%02x:%02x:%02x' '_PType=%d' ",
                                         mac[0], mac[1], mac[2], mac[3], mac[4], mac[5], type);
-
-                                t = strappend(s, buf);
                         }
 
-                        if (!t)
+                        k = strappend(s, buf);
+                        if (!k)
                                 return -ENOMEM;
 
                         free(s);
-                        s = t;
+                        s = k;
 
                         time = now(CLOCK_BOOTTIME);
 
                         /* Don't write expired packets */
-                        if(time - p->until <= 0) {
-                                free(s);
+                        if (time - p->until <= 0)
                                 continue;
-                        }
 
-                        memzero(buf, LINE_MAX);
                         sprintf(buf, "'_TTL=%lu' ", p->until);
 
-                        t = strappend(s, buf);
-                        if (!t)
+                        k = strappend(s, buf);
+                        if (!k)
                                 return -ENOMEM;
 
                         free(s);
-                        s = t;
+                        s = k;
 
                         r = lldp_read_system_name(p->packet, &length, &k);
                         if (r < 0)
@@ -528,6 +513,7 @@ int sd_lldp_save(sd_lldp *lldp, const char *lldp_file) {
                                         return -ENOMEM;
 
                                 k = strjoin(s, "'_NAME=", t, "' ", NULL);
+                                free(t);
                         }
 
                         if (!k)
@@ -536,28 +522,22 @@ int sd_lldp_save(sd_lldp *lldp, const char *lldp_file) {
                         free(s);
                         s = k;
 
-                        memzero(buf, LINE_MAX);
-
                         (void)lldp_read_system_capability(p->packet, &data);
 
                         sprintf(buf, "'_CAP=%x'", data);
 
-                        t = strappend(s, buf);
-                        if (!t)
+                        k = strappend(s, buf);
+                        if (!k)
                                 return -ENOMEM;
 
-                        fprintf(f, "%s\n", t);
-
                         free(s);
-                        free(t);
+                        s = k;
+
+                        fprintf(f, "%s\n", s);
                 }
         }
         r = 0;
 
-        s = NULL;
-        t = NULL;
-        k = NULL;
-
         fflush(f);
 
         if (ferror(f) || rename(temp_path, lldp_file) < 0) {