From 458e91300ee08abb6a3936f2549cc5d944c02107 Mon Sep 17 00:00:00 2001 From: Ilya Maximets Date: Fri, 1 Nov 2019 22:24:39 +0100 Subject: ofproto: Fix crash on PACKET_OUT due to recursive locking after upcall. Handling of OpenFlow PACKET_OUT implies pushing the packet through the datapath and packet processing inside the datapath could trigger an upcall. In case of system datapath, 'dpif_execute()' sends packet to the kernel module and returns. If any, upcall will be triggered inside the kernel and handled by a separate thread in userspace. But in case of userspace datapath full processing of the packet happens inside the 'dpif_execute()' in the same thread that handled PACKET_OUT. This causes an issue if upcall will lead to modification of flow rules. For example, it could happen while processing of 'learn' actions. Since whole handling of PACKET_OUT is protected by 'ofproto_mutex', OVS will assert on attempt to take it recursively while processing 'learn' actions: 0 __GI_raise (sig=sig@entry=6) 1 __GI_abort () 2 ovs_abort_valist () 3 ovs_abort () 4 ovs_mutex_lock_at (where=where@entry=0xad4199 "ofproto/ofproto.c:5391") 5 ofproto_flow_mod_learn () at ofproto/ofproto.c:5391 6 xlate_learn_action () at ofproto/ofproto-dpif-xlate.c:5378 <'learn' action found> 7 do_xlate_actions () at ofproto/ofproto-dpif-xlate.c:6893 8 xlate_recursively () at ofproto/ofproto-dpif-xlate.c:4233 9 xlate_table_action () at ofproto/ofproto-dpif-xlate.c:4361 10 in xlate_ofpact_resubmit () at ofproto/ofproto-dpif-xlate.c:4672 11 do_xlate_actions () at ofproto/ofproto-dpif-xlate.c:6773 12 xlate_actions () at ofproto/ofproto-dpif-xlate.c:7570 13 upcall_xlate () at ofproto/ofproto-dpif-upcall.c:1197 14 process_upcall () at ofproto/ofproto-dpif-upcall.c:1413 15 upcall_cb () at ofproto/ofproto-dpif-upcall.c:1315 16 dp_netdev_upcall (DPIF_UC_MISS) at lib/dpif-netdev.c:6236 17 handle_packet_upcall () at lib/dpif-netdev.c:6591 18 fast_path_processing () at lib/dpif-netdev.c:6709 19 dp_netdev_input__ () at lib/dpif-netdev.c:6797 20 dp_netdev_recirculate () at lib/dpif-netdev.c:6842 21 dp_execute_cb () at lib/dpif-netdev.c:7158 22 odp_execute_actions () at lib/odp-execute.c:794 23 dp_netdev_execute_actions () at lib/dpif-netdev.c:7332 24 dpif_netdev_execute () at lib/dpif-netdev.c:3725 25 dpif_netdev_operate () at lib/dpif-netdev.c:3756 26 dpif_operate () at lib/dpif.c:1367 27 dpif_execute () at lib/dpif.c:1321 28 packet_execute () at ofproto/ofproto-dpif.c:4760 29 ofproto_packet_out_finish () at ofproto/ofproto.c:3594 30 handle_packet_out () at ofproto/ofproto.c:3635 31 handle_single_part_openflow (OFPTYPE_PACKET_OUT) at ofproto/ofproto.c:8400 32 handle_openflow () at ofproto/ofproto.c:8587 33 ofconn_run () 34 connmgr_run () 35 ofproto_run () 36 bridge_run__ () 37 bridge_run () 38 main () Fix that by splitting the 'ofproto_packet_out_finish()' in two parts. First one that translates side-effects and requires holding 'ofproto_mutex' and the second that only pushes packet to datapath. The second part moved out of 'ofproto_mutex' because 'ofproto_mutex' is not required and actually should not be taken in order to avoid recursive locking. Reported-by: Anil Kumar Koli Reported-at: https://mail.openvswitch.org/pipermail/ovs-discuss/2019-April/048494.html Signed-off-by: Ilya Maximets Acked-by: Ben Pfaff --- ofproto/ofproto-dpif.c | 40 ++++++++++++++++++++++++++++++---------- ofproto/ofproto-provider.h | 12 +++++++++--- ofproto/ofproto.c | 29 +++++++++++++++++++++++++---- 3 files changed, 64 insertions(+), 17 deletions(-) diff --git a/ofproto/ofproto-dpif.c b/ofproto/ofproto-dpif.c index c7c70062c..3d6d72a40 100644 --- a/ofproto/ofproto-dpif.c +++ b/ofproto/ofproto-dpif.c @@ -4786,12 +4786,13 @@ ofproto_dpif_xcache_execute(struct ofproto_dpif *ofproto, } static void -packet_execute(struct ofproto *ofproto_, struct ofproto_packet_out *opo) +packet_execute_prepare(struct ofproto *ofproto_, + struct ofproto_packet_out *opo) OVS_REQUIRES(ofproto_mutex) { struct ofproto_dpif *ofproto = ofproto_dpif_cast(ofproto_); struct dpif_flow_stats stats; - struct dpif_execute execute; + struct dpif_execute *execute; struct ofproto_dpif_packet_out *aux = opo->aux; ovs_assert(aux); @@ -4800,22 +4801,40 @@ packet_execute(struct ofproto *ofproto_, struct ofproto_packet_out *opo) dpif_flow_stats_extract(opo->flow, opo->packet, time_msec(), &stats); ofproto_dpif_xcache_execute(ofproto, &aux->xcache, &stats); - execute.actions = aux->odp_actions.data; - execute.actions_len = aux->odp_actions.size; + execute = xzalloc(sizeof *execute); + execute->actions = xmemdup(aux->odp_actions.data, aux->odp_actions.size); + execute->actions_len = aux->odp_actions.size; pkt_metadata_from_flow(&opo->packet->md, opo->flow); - execute.packet = opo->packet; - execute.flow = opo->flow; - execute.needs_help = aux->needs_help; - execute.probe = false; - execute.mtu = 0; + execute->packet = opo->packet; + execute->flow = opo->flow; + execute->needs_help = aux->needs_help; + execute->probe = false; + execute->mtu = 0; /* Fix up in_port. */ ofproto_dpif_set_packet_odp_port(ofproto, opo->flow->in_port.ofp_port, opo->packet); - dpif_execute(ofproto->backer->dpif, &execute); ofproto_dpif_packet_out_delete(aux); + opo->aux = execute; +} + +static void +packet_execute(struct ofproto *ofproto_, struct ofproto_packet_out *opo) + OVS_EXCLUDED(ofproto_mutex) +{ + struct ofproto_dpif *ofproto = ofproto_dpif_cast(ofproto_); + struct dpif_execute *execute = opo->aux; + + if (!execute) { + return; + } + + dpif_execute(ofproto->backer->dpif, execute); + + free(CONST_CAST(struct nlattr *, execute->actions)); + free(execute); opo->aux = NULL; } @@ -6194,6 +6213,7 @@ const struct ofproto_class ofproto_dpif_class = { rule_get_stats, packet_xlate, packet_xlate_revert, + packet_execute_prepare, packet_execute, set_frag_handling, nxt_resume, diff --git a/ofproto/ofproto-provider.h b/ofproto/ofproto-provider.h index 7907d4bfb..d520a6380 100644 --- a/ofproto/ofproto-provider.h +++ b/ofproto/ofproto-provider.h @@ -1368,9 +1368,15 @@ struct ofproto_class { * packet_xlate_revert() calls have to be made in reverse order. */ void (*packet_xlate_revert)(struct ofproto *, struct ofproto_packet_out *); - /* Executes the datapath actions, translation side-effects, and stats as - * produced by ->packet_xlate(). The caller retains ownership of 'opo'. - */ + /* Translates side-effects, and stats as produced by ->packet_xlate(). + * Prepares to execute datapath actions. The caller retains ownership + * of 'opo'. */ + void (*packet_execute_prepare)(struct ofproto *, + struct ofproto_packet_out *opo); + + /* Executes the datapath actions. The caller retains ownership of 'opo'. + * Should be called after successful packet_execute_prepare(). + * No-op if called after packet_xlate_revert(). */ void (*packet_execute)(struct ofproto *, struct ofproto_packet_out *opo); /* Changes the OpenFlow IP fragment handling policy to 'frag_handling', diff --git a/ofproto/ofproto.c b/ofproto/ofproto.c index 6ffaced18..715da0607 100644 --- a/ofproto/ofproto.c +++ b/ofproto/ofproto.c @@ -3589,10 +3589,21 @@ ofproto_packet_out_revert(struct ofproto *ofproto, ofproto->ofproto_class->packet_xlate_revert(ofproto, opo); } +static void +ofproto_packet_out_prepare(struct ofproto *ofproto, + struct ofproto_packet_out *opo) + OVS_REQUIRES(ofproto_mutex) +{ + ofproto->ofproto_class->packet_execute_prepare(ofproto, opo); +} + +/* Execution of packet_out action in datapath could end up in upcall with + * subsequent flow translations and possible rule modifications. + * So, the caller should not hold 'ofproto_mutex'. */ static void ofproto_packet_out_finish(struct ofproto *ofproto, struct ofproto_packet_out *opo) - OVS_REQUIRES(ofproto_mutex) + OVS_EXCLUDED(ofproto_mutex) { ofproto->ofproto_class->packet_execute(ofproto, opo); } @@ -3635,10 +3646,13 @@ handle_packet_out(struct ofconn *ofconn, const struct ofp_header *oh) opo.version = p->tables_version; error = ofproto_packet_out_start(p, &opo); if (!error) { - ofproto_packet_out_finish(p, &opo); + ofproto_packet_out_prepare(p, &opo); } ovs_mutex_unlock(&ofproto_mutex); + if (!error) { + ofproto_packet_out_finish(p, &opo); + } ofproto_packet_out_uninit(&opo); return error; } @@ -8157,7 +8171,7 @@ do_bundle_commit(struct ofconn *ofconn, uint32_t id, uint16_t flags) } else if (be->type == OFPTYPE_GROUP_MOD) { ofproto_group_mod_finish(ofproto, &be->ogm, &req); } else if (be->type == OFPTYPE_PACKET_OUT) { - ofproto_packet_out_finish(ofproto, &be->opo); + ofproto_packet_out_prepare(ofproto, &be->opo); } } if (error) { @@ -8168,7 +8182,7 @@ do_bundle_commit(struct ofconn *ofconn, uint32_t id, uint16_t flags) /* Send error referring to the original message. */ ofconn_send_error(ofconn, be->msg, error); error = OFPERR_OFPBFC_MSG_FAILED; - + /* Revert. Undo all the changes made above. */ LIST_FOR_EACH_REVERSE_CONTINUE (be, node, &bundle->msg_list) { if (be->type == OFPTYPE_FLOW_MOD) { @@ -8187,6 +8201,13 @@ do_bundle_commit(struct ofconn *ofconn, uint32_t id, uint16_t flags) ovs_mutex_unlock(&ofproto_mutex); } + /* Executing remaining datapath actions. */ + LIST_FOR_EACH (be, node, &bundle->msg_list) { + if (be->type == OFPTYPE_PACKET_OUT) { + ofproto_packet_out_finish(ofproto, &be->opo); + } + } + /* The bundle is discarded regardless the outcome. */ ofp_bundle_remove__(ofconn, bundle); return error; -- 2.14.1