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84ad0af0bc
mini_Qdisc_pair::p_miniq is a double pointer to mini_Qdisc, initialized
in ingress_init() to point to net_device::miniq_ingress. ingress Qdiscs
access this per-net_device pointer in mini_qdisc_pair_swap(). Similar
for clsact Qdiscs and miniq_egress.
Unfortunately, after introducing RTNL-unlocked RTM_{NEW,DEL,GET}TFILTER
requests (thanks Hillf Danton for the hint), when replacing ingress or
clsact Qdiscs, for example, the old Qdisc ("@old") could access the same
miniq_{in,e}gress pointer(s) concurrently with the new Qdisc ("@new"),
causing race conditions [1] including a use-after-free bug in
mini_qdisc_pair_swap() reported by syzbot:
BUG: KASAN: slab-use-after-free in mini_qdisc_pair_swap+0x1c2/0x1f0 net/sched/sch_generic.c:1573
Write of size 8 at addr ffff888045b31308 by task syz-executor690/14901
...
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xd9/0x150 lib/dump_stack.c:106
print_address_description.constprop.0+0x2c/0x3c0 mm/kasan/report.c:319
print_report mm/kasan/report.c:430 [inline]
kasan_report+0x11c/0x130 mm/kasan/report.c:536
mini_qdisc_pair_swap+0x1c2/0x1f0 net/sched/sch_generic.c:1573
tcf_chain_head_change_item net/sched/cls_api.c:495 [inline]
tcf_chain0_head_change.isra.0+0xb9/0x120 net/sched/cls_api.c:509
tcf_chain_tp_insert net/sched/cls_api.c:1826 [inline]
tcf_chain_tp_insert_unique net/sched/cls_api.c:1875 [inline]
tc_new_tfilter+0x1de6/0x2290 net/sched/cls_api.c:2266
...
@old and @new should not affect each other. In other words, @old should
never modify miniq_{in,e}gress after @new, and @new should not update
@old's RCU state.
Fixing without changing sch_api.c turned out to be difficult (please
refer to Closes: for discussions). Instead, make sure @new's first call
always happen after @old's last call (in {ingress,clsact}_destroy()) has
finished:
In qdisc_graft(), return -EBUSY if @old has any ongoing filter requests,
and call qdisc_destroy() for @old before grafting @new.
Introduce qdisc_refcount_dec_if_one() as the counterpart of
qdisc_refcount_inc_nz() used for filter requests. Introduce a
non-static version of qdisc_destroy() that does a TCQ_F_BUILTIN check,
just like qdisc_put() etc.
Depends on patch "net/sched: Refactor qdisc_graft() for ingress and
clsact Qdiscs".
[1] To illustrate, the syzkaller reproducer adds ingress Qdiscs under
TC_H_ROOT (no longer possible after commit
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| .. | ||
| 9p | ||
| bluetooth | ||
| caif | ||
| iucv | ||
| mana | ||
| netfilter | ||
| netns | ||
| nfc | ||
| phonet | ||
| sctp | ||
| tc_act | ||
| 6lowpan.h | ||
| act_api.h | ||
| addrconf.h | ||
| af_ieee802154.h | ||
| af_rxrpc.h | ||
| af_unix.h | ||
| af_vsock.h | ||
| ah.h | ||
| amt.h | ||
| arp.h | ||
| atmclip.h | ||
| ax25.h | ||
| ax88796.h | ||
| bareudp.h | ||
| bond_3ad.h | ||
| bond_alb.h | ||
| bond_options.h | ||
| bonding.h | ||
| bpf_sk_storage.h | ||
| busy_poll.h | ||
| calipso.h | ||
| cfg80211-wext.h | ||
| cfg80211.h | ||
| cfg802154.h | ||
| checksum.h | ||
| cipso_ipv4.h | ||
| cls_cgroup.h | ||
| codel_impl.h | ||
| codel_qdisc.h | ||
| codel.h | ||
| compat.h | ||
| datalink.h | ||
| dcbevent.h | ||
| dcbnl.h | ||
| devlink.h | ||
| dropreason-core.h | ||
| dropreason.h | ||
| dsa_stubs.h | ||
| dsa.h | ||
| dsfield.h | ||
| dst_cache.h | ||
| dst_metadata.h | ||
| dst_ops.h | ||
| dst.h | ||
| erspan.h | ||
| esp.h | ||
| espintcp.h | ||
| ethoc.h | ||
| failover.h | ||
| fib_notifier.h | ||
| fib_rules.h | ||
| firewire.h | ||
| flow_dissector.h | ||
| flow_offload.h | ||
| flow.h | ||
| fou.h | ||
| fq_impl.h | ||
| fq.h | ||
| garp.h | ||
| gen_stats.h | ||
| genetlink.h | ||
| geneve.h | ||
| gre.h | ||
| gro_cells.h | ||
| gro.h | ||
| gtp.h | ||
| gue.h | ||
| handshake.h | ||
| hwbm.h | ||
| icmp.h | ||
| ieee80211_radiotap.h | ||
| ieee802154_netdev.h | ||
| if_inet6.h | ||
| ife.h | ||
| ila.h | ||
| inet_common.h | ||
| inet_connection_sock.h | ||
| inet_dscp.h | ||
| inet_ecn.h | ||
| inet_frag.h | ||
| inet_hashtables.h | ||
| inet_sock.h | ||
| inet_timewait_sock.h | ||
| inet6_connection_sock.h | ||
| inet6_hashtables.h | ||
| inetpeer.h | ||
| ioam6.h | ||
| ip_fib.h | ||
| ip_tunnels.h | ||
| ip_vs.h | ||
| ip.h | ||
| ip6_checksum.h | ||
| ip6_fib.h | ||
| ip6_route.h | ||
| ip6_tunnel.h | ||
| ipcomp.h | ||
| ipconfig.h | ||
| ipv6_frag.h | ||
| ipv6_stubs.h | ||
| ipv6.h | ||
| iw_handler.h | ||
| kcm.h | ||
| l3mdev.h | ||
| lag.h | ||
| lapb.h | ||
| lib80211.h | ||
| llc_c_ac.h | ||
| llc_c_ev.h | ||
| llc_c_st.h | ||
| llc_conn.h | ||
| llc_if.h | ||
| llc_pdu.h | ||
| llc_s_ac.h | ||
| llc_s_ev.h | ||
| llc_s_st.h | ||
| llc_sap.h | ||
| llc.h | ||
| lwtunnel.h | ||
| mac80211.h | ||
| mac802154.h | ||
| macsec.h | ||
| mctp.h | ||
| mctpdevice.h | ||
| mip6.h | ||
| mld.h | ||
| mpls_iptunnel.h | ||
| mpls.h | ||
| mptcp.h | ||
| mrp.h | ||
| ncsi.h | ||
| ndisc.h | ||
| neighbour.h | ||
| net_debug.h | ||
| net_failover.h | ||
| net_namespace.h | ||
| net_ratelimit.h | ||
| net_trackers.h | ||
| netdev_queues.h | ||
| netevent.h | ||
| netlabel.h | ||
| netlink.h | ||
| netprio_cgroup.h | ||
| netrom.h | ||
| nexthop.h | ||
| nl802154.h | ||
| nsh.h | ||
| p8022.h | ||
| page_pool.h | ||
| pie.h | ||
| ping.h | ||
| pkt_cls.h | ||
| pkt_sched.h | ||
| pptp.h | ||
| protocol.h | ||
| psample.h | ||
| psnap.h | ||
| raw.h | ||
| rawv6.h | ||
| red.h | ||
| regulatory.h | ||
| request_sock.h | ||
| rose.h | ||
| route.h | ||
| rpl.h | ||
| rsi_91x.h | ||
| rtnetlink.h | ||
| rtnh.h | ||
| sch_generic.h | ||
| scm.h | ||
| secure_seq.h | ||
| seg6_hmac.h | ||
| seg6_local.h | ||
| seg6.h | ||
| selftests.h | ||
| slhc_vj.h | ||
| smc.h | ||
| snmp.h | ||
| sock_reuseport.h | ||
| sock.h | ||
| Space.h | ||
| stp.h | ||
| strparser.h | ||
| switchdev.h | ||
| tc_wrapper.h | ||
| tcp_states.h | ||
| tcp.h | ||
| timewait_sock.h | ||
| tipc.h | ||
| tls_toe.h | ||
| tls.h | ||
| transp_v6.h | ||
| tso.h | ||
| tun_proto.h | ||
| udp_tunnel.h | ||
| udp.h | ||
| udplite.h | ||
| vsock_addr.h | ||
| vxlan.h | ||
| wext.h | ||
| x25.h | ||
| x25device.h | ||
| xdp_priv.h | ||
| xdp_sock_drv.h | ||
| xdp_sock.h | ||
| xdp.h | ||
| xfrm.h | ||
| xsk_buff_pool.h | ||