Review at https://gerrit.osmocom.org/168 gprs_gmm.c: Don't try to de-reference NULL mmctx There was a comment in the code that certain GMM messages require a valid mmctx pointer. However, nothing actually checked if that pointer was in fact non-NULL. We plainly crashed if a MS would send us the wrong message in the wrong state. Original patch by Harald Welte, but it broke message validity checking, resulting in sgsn_test failure. This re-implements the NULL check in a different way, as explained by in-code comment. Change-Id: I34b47b9e63691c9bc9904573000c74877217f679 --- M openbsc/src/gprs/gprs_gmm.c 1 file changed, 32 insertions(+), 0 deletions(-) git pull ssh://gerrit.osmocom.org:29418/openbsc refs/changes/68/168/1 diff --git a/openbsc/src/gprs/gprs_gmm.c b/openbsc/src/gprs/gprs_gmm.c index 1e10701..e788e3d 100644 --- a/openbsc/src/gprs/gprs_gmm.c +++ b/openbsc/src/gprs/gprs_gmm.c @@ -1339,6 +1339,15 @@ return rc; } + /* + * For a few messages, mmctx may be NULL. For most, we want to ensure a + * non-NULL mmctx. At the same time, we want to keep the message + * validity check intact, so that all message types appear in the + * switch statement and the default case thus means "unknown message". + * If we split the switch in two parts to check non-NULL halfway, the + * unknown-message check breaks, or we'd need to duplicate the switch + * cases in both parts. Just keep one large switch and add some gotos. + */ switch (gh->msg_type) { case GSM48_MT_GMM_RA_UPD_REQ: rc = gsm48_rx_gmm_ra_upd_req(mmctx, msg, llme); @@ -1348,20 +1357,30 @@ break; /* For all the following types mmctx can not be NULL */ case GSM48_MT_GMM_ID_RESP: + if (!mmctx) + goto null_mmctx; rc = gsm48_rx_gmm_id_resp(mmctx, msg); break; case GSM48_MT_GMM_STATUS: + if (!mmctx) + goto null_mmctx; rc = gsm48_rx_gmm_status(mmctx, msg); break; case GSM48_MT_GMM_DETACH_REQ: + if (!mmctx) + goto null_mmctx; rc = gsm48_rx_gmm_det_req(mmctx, msg); break; case GSM48_MT_GMM_DETACH_ACK: + if (!mmctx) + goto null_mmctx; LOGMMCTXP(LOGL_INFO, mmctx, "-> DETACH ACK\n"); mm_ctx_cleanup_free(mmctx, "GPRS DETACH ACK"); rc = 0; break; case GSM48_MT_GMM_ATTACH_COMPL: + if (!mmctx) + goto null_mmctx; /* only in case SGSN offered new P-TMSI */ LOGMMCTXP(LOGL_INFO, mmctx, "-> ATTACH COMPLETE\n"); mmctx_timer_stop(mmctx, 3350); @@ -1380,6 +1399,8 @@ osmo_signal_dispatch(SS_SGSN, S_SGSN_ATTACH, &sig_data); break; case GSM48_MT_GMM_RA_UPD_COMPL: + if (!mmctx) + goto null_mmctx; /* only in case SGSN offered new P-TMSI */ LOGMMCTXP(LOGL_INFO, mmctx, "-> ROUTING AREA UPDATE COMPLETE\n"); mmctx_timer_stop(mmctx, 3350); @@ -1398,6 +1419,8 @@ osmo_signal_dispatch(SS_SGSN, S_SGSN_UPDATE, &sig_data); break; case GSM48_MT_GMM_PTMSI_REALL_COMPL: + if (!mmctx) + goto null_mmctx; LOGMMCTXP(LOGL_INFO, mmctx, "-> PTMSI REALLLICATION COMPLETE\n"); mmctx_timer_stop(mmctx, 3350); mmctx->t3350_mode = GMM_T3350_MODE_NONE; @@ -1409,6 +1432,8 @@ rc = 0; break; case GSM48_MT_GMM_AUTH_CIPH_RESP: + if (!mmctx) + goto null_mmctx; rc = gsm48_rx_gmm_auth_ciph_resp(mmctx, msg); break; default: @@ -1419,6 +1444,13 @@ } return rc; + +null_mmctx: + LOGP(DMM, LOGL_ERROR, + "Received GSM 04.08 message type 0x%02x," + " but no MM context available\n", + gh->msg_type); + return -EINVAL; } static void mmctx_timer_cb(void *_mm) -- To view, visit https://gerrit.osmocom.org/168 To unsubscribe, visit https://gerrit.osmocom.org/settings Gerrit-MessageType: newchange Gerrit-Change-Id: I34b47b9e63691c9bc9904573000c74877217f679 Gerrit-PatchSet: 1 Gerrit-Project: openbsc Gerrit-Branch: master Gerrit-Owner: Neels Hofmeyr <nhofmeyr@sysmocom.de>