pimd: vrf may be NULL from pim_cmd_lookup_vrf

The call into pim_cmd_lookup_vrf may be NULL
and dereferencing it before ensuring that the
vrf pointer is non-NULL is a good way to crash.

A crash can be initiated in pim:

eva# show ip msdp vrf NOEXIST mesh-group
vtysh: error reading from pimd: Permission denied (13)Warning: closing connection to pimd because of an I/O error!
eva# 2022/08/15 11:47:38 [PHJDC-499N2][EC 100663314] STARVATION: task vtysh_rl_read (560b77f76de6) ran for 16777ms (cpu time 0ms)

eva#

Signed-off-by: Donald Sharp <sharpd@nvidia.com>

diff --git a/pimd/pim_cmd.c b/pimd/pim_cmd.c
index a3188128fa409a3daaebf2c366ba1345de222e13..c2453efa069ddb55932fe8e07bb4036e8760a3b2 100644 (file)
--- a/pimd/pim_cmd.c
+++ b/pimd/pim_cmd.c
@@ -5526,12 +5526,13 @@ DEFUN (show_ip_msdp_mesh_group,
        int idx = 2;
        struct pim_msdp_mg *mg;
        struct vrf *vrf = pim_cmd_lookup_vrf(vty, argv, argc, &idx);
-       struct pim_instance *pim = vrf->info;
+       struct pim_instance *pim;
        struct json_object *json = NULL;
 
        if (!vrf)
                return CMD_WARNING;
 
+       pim = vrf->info;
        /* Quick case: list is empty. */
        if (SLIST_EMPTY(&pim->msdp.mglist)) {
                if (uj)