diff options
authorMarcos Paulo de Souza <>2017-07-24 21:55:08 -0300
committerFlorian Westphal <>2017-07-25 03:06:29 +0200
commite870432649955d377a73ee5a72cb23f0f6b5e4c5 (patch)
parentb266523a03a282eabb76b46013ba43f7e47929c2 (diff)
labels: don't crash on NULL labelmap
When CONNLABEL_CFG isn't available (/etc/xtables/connlabel.conf), conntrack tool crashes: [marcos@Icarus ~]$ conntrack -l something nfct_labelmap_new: No such file or directory Segmentation fault (core dumped) I can see this problem in Fedora 26, because connlabel.conf does not come along the conntrack/libnetfilter packages. This problem happens because conntrack calls nfct_labelmap_new, which resides on libnetfilter_conntrack. So this lib returns NULL because CONNLABEL_CFG is not present, and then NULL is assigned to the global var called labelmap on conntrack. Later, get_label is called, passing NULL to the library, and __label_get_bit is called and deferences labelmap without check, which leads to a crash. With this patch the crash does not happen anymore, and an error message is displayed: conntrack -l something nfct_labelmap_new: No such file or directory conntrack v1.4.4 (conntrack-tools): unknown label 'something' Signed-off-by: Marcos Paulo de Souza <> Signed-off-by: Florian Westphal <>
1 files changed, 8 insertions, 2 deletions
diff --git a/src/conntrack/labels.c b/src/conntrack/labels.c
index 8048076..ef85b6e 100644
--- a/src/conntrack/labels.c
+++ b/src/conntrack/labels.c
@@ -51,8 +51,14 @@ static unsigned int hash_name(const char *name)
int __labelmap_get_bit(struct nfct_labelmap *m, const char *name)
- unsigned int i = hash_name(name);
- struct labelmap_bucket *list = m->map_name[i];
+ struct labelmap_bucket *list;
+ unsigned int i;
+ if (!m)
+ return -1;
+ i = hash_name(name);
+ list = m->map_name[i];
while (list) {
if (strcmp(name, list->name) == 0)