[libvirt] [PATCH v1 01/23] virtlockd: Don't SIGSEGV on SIGUSR1

[Michal Privoznik]

So we have this mechanism that on SIGUSR1 the virtlockd dumps its
internal state into a JSON file, reexec itself and the reloads
the internal state back. However, there's a bug in our
implementation:

  (gdb) signal SIGUSR1
  Continuing with signal SIGUSR1.
  [Thread 0x7fd094f7b700 (LWP 10602) exited]
  process 10600 is executing new program: /home/zippy/work/libvirt/libvirt.git/src/virtlockd
  warning: Could not load shared library symbols for linux-vdso.so.1.
  Do you need "set solib-search-path" or "set sysroot"?
  [Thread debugging using libthread_db enabled]
  Using host libthread_db library "/lib64/libthread_db.so.1".
  [New Thread 0x7fb28bc3c700 (LWP 14501)]

  Program received signal SIGSEGV, Segmentation fault.
  0x00007fb29133d530 in virExpandN (ptrptr=0x70, size=8, countptr=0x68, add=1, report=true, domcode=7, filename=0x7fb29138aeab "rpc/virnetserver.c", funcname=0x7fb29138b680 <__FUNCTION__.15821> "virNetServerAddProgram", linenr=661) at util/viralloc.c:288
  288         if (*countptr + add < *countptr) {
  (gdb) bt
  #0  0x00007fb29133d530 in virExpandN (ptrptr=0x70, size=8, countptr=0x68, add=1, report=true, domcode=7, filename=0x7fb29138aeab "rpc/virnetserver.c", funcname=0x7fb29138b680 <__FUNCTION__.15821> "virNetServerAddProgram", linenr=661) at util/viralloc.c:288
  #1  0x00007fb29132a267 in virNetServerAddProgram (srv=0x0, prog=0x7fb2915d08b0) at rpc/virnetserver.c:661
  #2  0x00007fb29131f27f in main (argc=1, argv=0x7fff8f771298) at locking/lock_daemon.c:1445

Notice the NULL @srv passed to frame 2? Usually, the @srv
variable is initialized on fresh start. However, in case of
daemon reload, the code path that is responsible for initializing
the value was not triggered and therefore we crashed immediately.
Fix this by always setting the variable.

Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
---
 src/locking/lock_daemon.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/locking/lock_daemon.c b/src/locking/lock_daemon.c
index 55fc0c3..56db959 100644
--- a/src/locking/lock_daemon.c
+++ b/src/locking/lock_daemon.c
@@ -1366,6 +1366,8 @@ int main(int argc, char **argv) {
             ret = VIR_LOCK_DAEMON_ERR_NETWORK;
             goto cleanup;
         }
+    } else if (rv == 1) {
+        srv = virNetDaemonGetServer(lockDaemon->dmn, 0);
     }
 
     if (timeout != -1) {
-- 
2.4.9