networkd: fix NULL pointer (#3523)

Not every link has kind associated with it.

(gdb) r
Starting program: /home/sus/tt/systemd/systemd-networkd
Missing separate debuginfos, use: dnf debuginfo-install
glibc-2.23.1-7.fc24.x86_64
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".
vboxnet0: Gained IPv6LL
wlp3s0: Gained IPv6LL
enp0s25: Gained IPv6LL
Enumeration completed

Program received signal SIGSEGV, Segmentation fault.
0x00007ffff6e27ade in __strcmp_sse2_unaligned () from /lib64/libc.so.6
(gdb) bt
src/network/networkd-link.c:2008
src/network/networkd-link.c:2059
src/network/networkd-link.c:2442
m=0x555555704a30, userdata=0x55555570bfe0) at src/network/networkd-link.c:2497
at src/libsystemd/sd-netlink/sd-netlink.c:347
src/libsystemd/sd-netlink/sd-netlink.c:402
src/libsystemd/sd-netlink/sd-netlink.c:432
userdata=0x5555556f7470) at src/libsystemd/sd-netlink/sd-netlink.c:739
src/libsystemd/sd-event/sd-event.c:2275
src/libsystemd/sd-event/sd-event.c:2626
timeout=18446744073709551615) at src/libsystemd/sd-event/sd-event.c:2685
bus=0x5555556f9af0, name=0x555555692315 "org.freedesktop.network1",
timeout=30000000,
    check_idle=0x55555556ac84 <manager_check_idle>, userdata=0x5555556f6b20) at
src/shared/bus-util.c:134
src/network/networkd-manager.c:1128
src/network/networkd.c:127
(gdb) f 1
src/network/networkd-link.c:2008
2008            if (link->network->bridge || streq("bridge", link->kind)) {
(gdb) p link->kind
$1 = 0x0

diff --git a/src/network/networkd-link.c b/src/network/networkd-link.c
index 0302f57f2676b99c8aaf342bbf4ba4fd1730d442..044f934e5ffb5523d060adaf6e297c8fe59652ed 100644 (file)
--- a/src/network/networkd-link.c
+++ b/src/network/networkd-link.c
@@ -2005,7 +2005,7 @@ static int link_joined(Link *link) {
                         log_link_error_errno(link, r, "Could not set bridge message: %m");
         }
 
-        if (link->network->bridge || streq("bridge", link->kind)) {
+        if (link->network->bridge || streq_ptr("bridge", link->kind)) {
                 r = link_set_bridge_vlan(link);
                 if (r < 0)
                         log_link_error_errno(link, r, "Could not set bridge vlan: %m");