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Date: Wed, 26 Jul 2023 15:54:12 +0200
From: Eric Dumazet <edumazet@...gle.com>
To: Kuniyuki Iwashima <kuniyu@...zon.com>
Cc: "David S. Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>, Vinicius Costa Gomes <vinicius.gomes@...el.com>,
Jamal Hadi Salim <jhs@...atatu.com>, Cong Wang <xiyou.wangcong@...il.com>,
Jiri Pirko <jiri@...nulli.us>, Vedang Patel <vedang.patel@...el.com>,
Kuniyuki Iwashima <kuni1840@...il.com>, netdev@...r.kernel.org,
syzkaller <syzkaller@...glegroups.com>
Subject: Re: [PATCH v1 net] net/sched: taprio: Limit TCA_TAPRIO_ATTR_SCHED_CYCLE_TIME
to INT_MAX.
On Wed, Jul 26, 2023 at 3:15 AM Kuniyuki Iwashima <kuniyu@...zon.com> wrote:
>
> syzkaller found a zero division error [0] in div_s64_rem() called from
> get_cycle_time_elapsed(), where sched->cycle_time is the divisor.
>
> We have tests in parse_taprio_schedule() so that cycle_time will never
> be 0, and actually cycle_time is not 0 in get_cycle_time_elapsed().
>
> The problem is that the types of divisor are different; cycle_time is
> s64, but the argument of div_s64_rem() is s32.
>
> syzkaller fed this input and 0x100000000 is cast to s32 to be 0.
>
> @TCA_TAPRIO_ATTR_SCHED_CYCLE_TIME={0xc, 0x8, 0x100000000}
>
> We use s64 for cycle_time to cast it to ktime_t, so let's keep it and
> set min/max for cycle_time.
>
> [0]:
> divide error: 0000 [#1] PREEMPT SMP KASAN NOPTI
> CPU: 1 PID: 103 Comm: kworker/1:3 Not tainted 6.5.0-rc1-00330-g60cc1f7d0605 #3
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
> Workqueue: ipv6_addrconf addrconf_dad_work
> RIP: 0010:div_s64_rem include/linux/math64.h:42 [inline]
> RIP: 0010:get_cycle_time_elapsed net/sched/sch_taprio.c:223 [inline]
> RIP: 0010:find_entry_to_transmit+0x252/0x7e0 net/sched/sch_taprio.c:344
> Code: 3c 02 00 0f 85 5e 05 00 00 48 8b 4c 24 08 4d 8b bd 40 01 00 00 48 8b 7c 24 48 48 89 c8 4c 29 f8 48 63 f7 48 99 48 89 74 24 70 <48> f7 fe 48 29 d1 48 8d 04 0f 49 89 cc 48 89 44 24 20 49 8d 85 10
> RSP: 0018:ffffc90000acf260 EFLAGS: 00010206
> RAX: 177450e0347560cf RBX: 0000000000000000 RCX: 177450e0347560cf
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000100000000
> RBP: 0000000000000056 R08: 0000000000000000 R09: ffffed10020a0934
> R10: ffff8880105049a7 R11: ffff88806cf3a520 R12: ffff888010504800
> R13: ffff88800c00d800 R14: ffff8880105049a0 R15: 0000000000000000
> FS: 0000000000000000(0000) GS:ffff88806cf00000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f0edf84f0e8 CR3: 000000000d73c002 CR4: 0000000000770ee0
> PKRU: 55555554
> Call Trace:
> <TASK>
> get_packet_txtime net/sched/sch_taprio.c:508 [inline]
> taprio_enqueue_one+0x900/0xff0 net/sched/sch_taprio.c:577
> taprio_enqueue+0x378/0xae0 net/sched/sch_taprio.c:658
> dev_qdisc_enqueue+0x46/0x170 net/core/dev.c:3732
> __dev_xmit_skb net/core/dev.c:3821 [inline]
> __dev_queue_xmit+0x1b2f/0x3000 net/core/dev.c:4169
> dev_queue_xmit include/linux/netdevice.h:3088 [inline]
> neigh_resolve_output net/core/neighbour.c:1552 [inline]
> neigh_resolve_output+0x4a7/0x780 net/core/neighbour.c:1532
> neigh_output include/net/neighbour.h:544 [inline]
> ip6_finish_output2+0x924/0x17d0 net/ipv6/ip6_output.c:135
> __ip6_finish_output+0x620/0xaa0 net/ipv6/ip6_output.c:196
> ip6_finish_output net/ipv6/ip6_output.c:207 [inline]
> NF_HOOK_COND include/linux/netfilter.h:292 [inline]
> ip6_output+0x206/0x410 net/ipv6/ip6_output.c:228
> dst_output include/net/dst.h:458 [inline]
> NF_HOOK.constprop.0+0xea/0x260 include/linux/netfilter.h:303
> ndisc_send_skb+0x872/0xe80 net/ipv6/ndisc.c:508
> ndisc_send_ns+0xb5/0x130 net/ipv6/ndisc.c:666
> addrconf_dad_work+0xc14/0x13f0 net/ipv6/addrconf.c:4175
> process_one_work+0x92c/0x13a0 kernel/workqueue.c:2597
> worker_thread+0x60f/0x1240 kernel/workqueue.c:2748
> kthread+0x2fe/0x3f0 kernel/kthread.c:389
> ret_from_fork+0x2c/0x50 arch/x86/entry/entry_64.S:308
> </TASK>
> Modules linked in:
>
> Fixes: 4cfd5779bd6e ("taprio: Add support for txtime-assist mode")
> Reported-by: syzkaller <syzkaller@...glegroups.com>
> Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com>
> ---
> net/sched/sch_taprio.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c
> index 717ae51d94a0..72808acb5435 100644
> --- a/net/sched/sch_taprio.c
> +++ b/net/sched/sch_taprio.c
> @@ -1015,6 +1015,11 @@ static const struct nla_policy taprio_tc_policy[TCA_TAPRIO_TC_ENTRY_MAX + 1] = {
> TC_FP_PREEMPTIBLE),
> };
>
> +static struct netlink_range_validation_signed taprio_cycle_time_range = {
> + .min = 1,
> + .max = INT_MAX,
> +};
> +
> static const struct nla_policy taprio_policy[TCA_TAPRIO_ATTR_MAX + 1] = {
> [TCA_TAPRIO_ATTR_PRIOMAP] = {
> .len = sizeof(struct tc_mqprio_qopt)
> @@ -1023,7 +1028,8 @@ static const struct nla_policy taprio_policy[TCA_TAPRIO_ATTR_MAX + 1] = {
> [TCA_TAPRIO_ATTR_SCHED_BASE_TIME] = { .type = NLA_S64 },
> [TCA_TAPRIO_ATTR_SCHED_SINGLE_ENTRY] = { .type = NLA_NESTED },
> [TCA_TAPRIO_ATTR_SCHED_CLOCKID] = { .type = NLA_S32 },
> - [TCA_TAPRIO_ATTR_SCHED_CYCLE_TIME] = { .type = NLA_S64 },
> + [TCA_TAPRIO_ATTR_SCHED_CYCLE_TIME] =
> + NLA_POLICY_FULL_RANGE_SIGNED(NLA_S64, &taprio_cycle_time_range),
> [TCA_TAPRIO_ATTR_SCHED_CYCLE_TIME_EXTENSION] = { .type = NLA_S64 },
> [TCA_TAPRIO_ATTR_FLAGS] = { .type = NLA_U32 },
> [TCA_TAPRIO_ATTR_TXTIME_DELAY] = { .type = NLA_U32 },
> --
> 2.30.2
>
Not sure this is enough (syzbot could very well find other ways to
trigger bugs caused by overflows)
What about setup_txtime() ? It seems possible to have overflows there...
What about adding to your patch the following ?
diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c
index 717ae51d94a0ae4f45317e8ba86f51ab4ac41aa6..a4bdc5d8bd6fc546bc835c953db81cdaf7285a40
100644
--- a/net/sched/sch_taprio.c
+++ b/net/sched/sch_taprio.c
@@ -1158,7 +1158,10 @@ static int parse_taprio_schedule(struct
taprio_sched *q, struct nlattr **tb,
NL_SET_ERR_MSG(extack, "'cycle_time' can never be 0");
return -EINVAL;
}
-
+ if (cycle > INT_MAX) {
+ NL_SET_ERR_MSG(extack, "'cycle_time' is too big");
+ return -EINVAL;
+ }
new->cycle_time = cycle;
}
@@ -1347,7 +1350,7 @@ static void setup_txtime(struct taprio_sched *q,
struct sched_gate_list *sched, ktime_t base)
{
struct sched_entry *entry;
- u32 interval = 0;
+ u64 interval = 0;
list_for_each_entry(entry, &sched->entries, list) {
entry->next_txtime = ktime_add_ns(base, interval);
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