dco_linux: validate tun interface before fetching stats

If dco_get_peer_stats() is called with an uninitialized c->c1.tuntap it
results in a segfault. This issue happens when a client who has not
connected to any server:
  - has --management and exits,
  - has --management and a management interface client issues either
    `bytecount` or `status` or
  - if SIGUSR2 is sent to it.

Add a check to ensure the tun interface was set up before attempting to
retrieve peer statistics.

Change-Id: I40c11864745cc1619cb9cbf490b168f90feb5eac
Signed-off-by: Ralf Lici <ralf@mandelbit.com>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <20250902164521.23145-1-gert@greenie.muc.de>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg32768.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>

diff --git a/src/openvpn/dco_linux.c b/src/openvpn/dco_linux.c
index 6115d5175302d1d286a56124a3ae3d38f8854682..40674e7f4cdbd5fb841155a1a943792535ef88b7 100644 (file)
--- a/src/openvpn/dco_linux.c
+++ b/src/openvpn/dco_linux.c
@@ -1139,6 +1139,8 @@ dco_do_read(dco_context_t *dco)
 static int
 dco_get_peer(dco_context_t *dco, int peer_id, const bool raise_sigusr1_on_err)
 {
+    ASSERT(dco);
+
     /* peer_id == -1 means "dump all peers", but this is allowed in MP mode only.
      * If it happens in P2P mode it means that the DCO peer was deleted and we
      * can simply bail out
@@ -1182,6 +1184,11 @@ nla_put_failure:
 int
 dco_get_peer_stats(struct context *c, const bool raise_sigusr1_on_err)
 {
+    if (!c->c1.tuntap || c->c1.tuntap->dco.ifindex == 0)
+    {
+        return -1;
+    }
+
     return dco_get_peer(&c->c1.tuntap->dco, c->c2.tls_multi->dco_peer_id, raise_sigusr1_on_err);
 }