WSL2-Linux-Kernel/net/sched
Frederick Lawler 96398560f2 net: sched: disallow noqueue for qdisc classes
While experimenting with applying noqueue to a classful queue discipline,
we discovered a NULL pointer dereference in the __dev_queue_xmit()
path that generates a kernel OOPS:

    # dev=enp0s5
    # tc qdisc replace dev $dev root handle 1: htb default 1
    # tc class add dev $dev parent 1: classid 1:1 htb rate 10mbit
    # tc qdisc add dev $dev parent 1:1 handle 10: noqueue
    # ping -I $dev -w 1 -c 1 1.1.1.1

[    2.172856] BUG: kernel NULL pointer dereference, address: 0000000000000000
[    2.173217] #PF: supervisor instruction fetch in kernel mode
...
[    2.178451] Call Trace:
[    2.178577]  <TASK>
[    2.178686]  htb_enqueue+0x1c8/0x370
[    2.178880]  dev_qdisc_enqueue+0x15/0x90
[    2.179093]  __dev_queue_xmit+0x798/0xd00
[    2.179305]  ? _raw_write_lock_bh+0xe/0x30
[    2.179522]  ? __local_bh_enable_ip+0x32/0x70
[    2.179759]  ? ___neigh_create+0x610/0x840
[    2.179968]  ? eth_header+0x21/0xc0
[    2.180144]  ip_finish_output2+0x15e/0x4f0
[    2.180348]  ? dst_output+0x30/0x30
[    2.180525]  ip_push_pending_frames+0x9d/0xb0
[    2.180739]  raw_sendmsg+0x601/0xcb0
[    2.180916]  ? _raw_spin_trylock+0xe/0x50
[    2.181112]  ? _raw_spin_unlock_irqrestore+0x16/0x30
[    2.181354]  ? get_page_from_freelist+0xcd6/0xdf0
[    2.181594]  ? sock_sendmsg+0x56/0x60
[    2.181781]  sock_sendmsg+0x56/0x60
[    2.181958]  __sys_sendto+0xf7/0x160
[    2.182139]  ? handle_mm_fault+0x6e/0x1d0
[    2.182366]  ? do_user_addr_fault+0x1e1/0x660
[    2.182627]  __x64_sys_sendto+0x1b/0x30
[    2.182881]  do_syscall_64+0x38/0x90
[    2.183085]  entry_SYSCALL_64_after_hwframe+0x63/0xcd
...
[    2.187402]  </TASK>

Previously in commit d66d6c3152 ("net: sched: register noqueue
qdisc"), NULL was set for the noqueue discipline on noqueue init
so that __dev_queue_xmit() falls through for the noqueue case. This
also sets a bypass of the enqueue NULL check in the
register_qdisc() function for the struct noqueue_disc_ops.

Classful queue disciplines make it past the NULL check in
__dev_queue_xmit() because the discipline is set to htb (in this case),
and then in the call to __dev_xmit_skb(), it calls into htb_enqueue()
which grabs a leaf node for a class and then calls qdisc_enqueue() by
passing in a queue discipline which assumes ->enqueue() is not set to NULL.

Fix this by not allowing classes to be assigned to the noqueue
discipline. Linux TC Notes states that classes cannot be set to
the noqueue discipline. [1] Let's enforce that here.

Links:
1. https://linux-tc-notes.sourceforge.net/tc/doc/sch_noqueue.txt

Fixes: d66d6c3152 ("net: sched: register noqueue qdisc")
Cc: stable@vger.kernel.org
Signed-off-by: Frederick Lawler <fred@cloudflare.com>
Reviewed-by: Jakub Sitnicki <jakub@cloudflare.com>
Link: https://lore.kernel.org/r/20230109163906.706000-1-fred@cloudflare.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2023-01-10 18:19:32 -08:00
..
Kconfig
Makefile
act_api.c
act_bpf.c
act_connmark.c
act_csum.c
act_ct.c
act_ctinfo.c
act_gact.c
act_gate.c
act_ife.c
act_ipt.c
act_meta_mark.c
act_meta_skbprio.c
act_meta_skbtcindex.c
act_mirred.c
act_mpls.c
act_nat.c
act_pedit.c
act_police.c
act_sample.c
act_simple.c
act_skbedit.c
act_skbmod.c
act_tunnel_key.c
act_vlan.c
cls_api.c
cls_basic.c
cls_bpf.c
cls_cgroup.c
cls_flow.c
cls_flower.c
cls_fw.c
cls_matchall.c
cls_route.c
cls_rsvp.c
cls_rsvp.h
cls_rsvp6.c
cls_tcindex.c
cls_u32.c
em_canid.c
em_cmp.c
em_ipset.c
em_ipt.c
em_meta.c
em_nbyte.c
em_text.c
em_u32.c
ematch.c
sch_api.c net: sched: disallow noqueue for qdisc classes 2023-01-10 18:19:32 -08:00
sch_atm.c
sch_blackhole.c
sch_cake.c
sch_cbq.c
sch_cbs.c
sch_choke.c
sch_codel.c
sch_drr.c
sch_dsmark.c
sch_etf.c
sch_ets.c
sch_fifo.c
sch_fq.c
sch_fq_codel.c
sch_fq_pie.c
sch_frag.c
sch_generic.c
sch_gred.c
sch_hfsc.c
sch_hhf.c
sch_htb.c
sch_ingress.c
sch_mq.c
sch_mqprio.c
sch_multiq.c
sch_netem.c
sch_pie.c
sch_plug.c
sch_prio.c
sch_qfq.c
sch_red.c
sch_sfb.c
sch_sfq.c
sch_skbprio.c
sch_taprio.c
sch_tbf.c
sch_teql.c