isisd: Fix CID 1568134 (Null pointer dereference)

Null check `isis` pointer before dereferencing it.

Fixes this coverity issue:

*** CID 1568134:  Null pointer dereferences  (NULL_RETURNS)
/isisd/isis_zebra.c: 1146 in isis_zebra_process_srv6_locator_chunk()
1140                    "prefix %pFX, block_len %u, node_len %u, func_len %u, arg_len %u",
1141                    chunk->locator_name, &chunk->prefix, chunk->block_bits_length,
1142                    chunk->node_bits_length, chunk->function_bits_length,
1143                    chunk->argument_bits_length);
1144
1145            /* Walk through all areas of the ISIS instance */
>>>     CID 1568134:  Null pointer dereferences  (NULL_RETURNS)
>>>     Dereferencing "isis", which is known to be "NULL".
1146            for (ALL_LIST_ELEMENTS_RO(isis->area_list, node, area)) {
1147                    if (strncmp(area->srv6db.config.srv6_locator_name,
1148                                chunk->locator_name,
1149                                sizeof(area->srv6db.config.srv6_locator_name)) != 0)
1150                            continue;
1151

Signed-off-by: Carmine Scarpitta <cscarpit@cisco.com>

diff --git a/isisd/isis_zebra.c b/isisd/isis_zebra.c
index 378d78efe4495a27cc2242d24a9bd7658fd67f8d..788618ef8b2f8fe09f7a67eee6a9dda4e09404a1 100644 (file)
--- a/isisd/isis_zebra.c
+++ b/isisd/isis_zebra.c
@@ -1136,6 +1136,9 @@ static int isis_zebra_process_srv6_locator_chunk(ZAPI_CALLBACK_ARGS)
        enum srv6_endpoint_behavior_codepoint behavior;
        bool allocated = false;
 
+       if (!isis)
+               return -1;
+
        /* Decode the received zebra message */
        s = zclient->ibuf;
        if (zapi_srv6_locator_chunk_decode(s, chunk) < 0)