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Message-ID: <857dceaa-7ef7-40c6-b519-2781acaa8209@intel.com>
Date: Fri, 30 Aug 2024 15:02:40 +0200
From: Alexander Lobakin <aleksander.lobakin@...el.com>
To: Dmitry Antipov <dmantipov@...dex.ru>
CC: Vinicius Costa Gomes <vinicius.gomes@...el.com>, Jakub Kicinski
<kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, <netdev@...r.kernel.org>,
<lvc-project@...uxtesting.org>
Subject: Re: [PATCH v3 3/3] net: sched: use RCU read-side critical section in
taprio_dump()
From: Dmitry Antipov <dmantipov@...dex.ru>
Date: Fri, 30 Aug 2024 13:16:33 +0300
> Fix possible use-after-free in 'taprio_dump()' by adding RCU
> read-side critical section there. Never seen on x86 but reproduced
> on a KASAN-enabled arm64 system (note that original issue was found at
"the original issue"?
> https://syzkaller.appspot.com/bug?extid=b65e0af58423fc8a73aa on arm64):
You need put all the links at the end of the commitmsg and leave only a
reference here.
"(note that original issue was found at [1])"
Then, before your SoB:
[1] https://syzkaller.appspot.com/bug?extid=b65e0af58423fc8a73aa
I think you could shorten these splats by dropping unrelated parts (see
below):
>
> [ 1601.079132][T15862] BUG: KASAN: slab-use-after-free in taprio_dump+0xa0c/0xbb0
> [ 1601.082101][T15862] Read of size 4 at addr ffff0000d4bb88f8 by task repro/15862
> [ 1601.085149][T15862]
> [ 1601.093445][T15862] CPU: 0 UID: 0 PID: 15862 Comm: repro Not tainted 6.11.0-rc1-00293-gdefaf1a2113a-dirty #2
> [ 1601.100771][T15862] Hardware name: QEMU QEMU Virtual Machine, BIOS edk2-20240524-5.fc40 05/24/2024
> [ 1601.106651][T15862] Call trace:
The below 4 lines can be dropped.
> [ 1601.107395][T15862] dump_backtrace+0x20c/0x220
> [ 1601.108397][T15862] show_stack+0x2c/0x40
> [ 1601.109220][T15862] dump_stack_lvl+0xf8/0x174
> [ 1601.110041][T15862] print_report+0x170/0x4d8
Up to here.
> [ 1601.110848][T15862] kasan_report+0xb8/0x1d4
> [ 1601.111991][T15862] __asan_report_load4_noabort+0x20/0x2c
> [ 1601.112880][T15862] taprio_dump+0xa0c/0xbb0
> [ 1601.113725][T15862] tc_fill_qdisc+0x540/0x1020
> [ 1601.114586][T15862] qdisc_notify.isra.0+0x330/0x3a0
> [ 1601.115506][T15862] tc_modify_qdisc+0x7b8/0x1838
> [ 1601.116378][T15862] rtnetlink_rcv_msg+0x3c8/0xc20
> [ 1601.117320][T15862] netlink_rcv_skb+0x1f8/0x3d4
> [ 1601.118164][T15862] rtnetlink_rcv+0x28/0x40
> [ 1601.119037][T15862] netlink_unicast+0x51c/0x790
> [ 1601.119874][T15862] netlink_sendmsg+0x79c/0xc20
> [ 1601.120706][T15862] __sock_sendmsg+0xe0/0x1a0
> [ 1601.121802][T15862] ____sys_sendmsg+0x6c0/0x840
> [ 1601.122722][T15862] ___sys_sendmsg+0x1ac/0x1f0
> [ 1601.123653][T15862] __sys_sendmsg+0x110/0x1d0
> [ 1601.124459][T15862] __arm64_sys_sendmsg+0x74/0xb0
Drop the below lines up to (not including) "Allocated by task".
> [ 1601.125316][T15862] invoke_syscall+0x88/0x2e0
> [ 1601.126155][T15862] el0_svc_common.constprop.0+0xe4/0x2a0
> [ 1601.127051][T15862] do_el0_svc+0x44/0x60
> [ 1601.127837][T15862] el0_svc+0x50/0x184
> [ 1601.128639][T15862] el0t_64_sync_handler+0x120/0x12c
> [ 1601.129505][T15862] el0t_64_sync+0x190/0x194
> [ 1601.130591][T15862]
> [ 1601.131361][T15862] Allocated by task 15857:
> [ 1601.132224][T15862] kasan_save_stack+0x3c/0x70
> [ 1601.133193][T15862] kasan_save_track+0x20/0x3c
> [ 1601.134102][T15862] kasan_save_alloc_info+0x40/0x60
> [ 1601.134955][T15862] __kasan_kmalloc+0xd4/0xe0
> [ 1601.135965][T15862] __kmalloc_cache_noprof+0x194/0x334
> [ 1601.136874][T15862] taprio_change+0x45c/0x2fe0
> [ 1601.137859][T15862] tc_modify_qdisc+0x6a8/0x1838
> [ 1601.138838][T15862] rtnetlink_rcv_msg+0x3c8/0xc20
> [ 1601.139799][T15862] netlink_rcv_skb+0x1f8/0x3d4
> [ 1601.140664][T15862] rtnetlink_rcv+0x28/0x40
> [ 1601.141725][T15862] netlink_unicast+0x51c/0x790
> [ 1601.142662][T15862] netlink_sendmsg+0x79c/0xc20
> [ 1601.143523][T15862] __sock_sendmsg+0xe0/0x1a0
> [ 1601.144445][T15862] ____sys_sendmsg+0x6c0/0x840
> [ 1601.145467][T15862] ___sys_sendmsg+0x1ac/0x1f0
> [ 1601.146410][T15862] __sys_sendmsg+0x110/0x1d0
> [ 1601.147293][T15862] __arm64_sys_sendmsg+0x74/0xb0
Same here, the below 6 lines are not needed.
> [ 1601.148116][T15862] invoke_syscall+0x88/0x2e0
> [ 1601.148912][T15862] el0_svc_common.constprop.0+0xe4/0x2a0
> [ 1601.149754][T15862] do_el0_svc+0x44/0x60
> [ 1601.150532][T15862] el0_svc+0x50/0x184
> [ 1601.151438][T15862] el0t_64_sync_handler+0x120/0x12c
> [ 1601.152311][T15862] el0t_64_sync+0x190/0x194
> [ 1601.153208][T15862]
> [ 1601.153751][T15862] Freed by task 6192:
> [ 1601.154491][T15862] kasan_save_stack+0x3c/0x70
> [ 1601.155491][T15862] kasan_save_track+0x20/0x3c
> [ 1601.156521][T15862] kasan_save_free_info+0x4c/0x80
> [ 1601.157357][T15862] poison_slab_object+0x110/0x160
> [ 1601.158300][T15862] __kasan_slab_free+0x3c/0x74
> [ 1601.159265][T15862] kfree+0x134/0x3c0
> [ 1601.160068][T15862] taprio_free_sched_cb+0x18c/0x220
> [ 1601.161046][T15862] rcu_core+0x920/0x1b7c
> [ 1601.161906][T15862] rcu_core_si+0x10/0x1c
> [ 1601.162693][T15862] handle_softirqs+0x2e8/0xd64
> [ 1601.163518][T15862] __do_softirq+0x14/0x20
>
> Signed-off-by: Dmitry Antipov <dmantipov@...dex.ru>
> ---
> v3: tweak commit message as suggested by Vinicius
> v2: added to the series
> ---
> net/sched/sch_taprio.c | 37 +++++++++++++++++++++----------------
> 1 file changed, 21 insertions(+), 16 deletions(-)
>
> diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c
> index 9f4e004cdb8b..f31feca381c4 100644
> --- a/net/sched/sch_taprio.c
> +++ b/net/sched/sch_taprio.c
> @@ -2374,9 +2374,6 @@ static int taprio_dump(struct Qdisc *sch, struct sk_buff *skb)
> struct tc_mqprio_qopt opt = { 0 };
> struct nlattr *nest, *sched_nest;
>
> - oper = rtnl_dereference(q->oper_sched);
> - admin = rtnl_dereference(q->admin_sched);
> -
> mqprio_qopt_reconstruct(dev, &opt);
>
> nest = nla_nest_start_noflag(skb, TCA_OPTIONS);
> @@ -2397,29 +2394,37 @@ static int taprio_dump(struct Qdisc *sch, struct sk_buff *skb)
> nla_put_u32(skb, TCA_TAPRIO_ATTR_TXTIME_DELAY, q->txtime_delay))
> goto options_error;
>
> + rcu_read_lock();
> +
> + oper = rtnl_dereference(q->oper_sched);
> + admin = rtnl_dereference(q->admin_sched);
> +
> if (oper && taprio_dump_tc_entries(skb, q, oper))
> - goto options_error;
> + goto unlock;
>
> if (oper && dump_schedule(skb, oper))
> - goto options_error;
> + goto unlock;
>
> - if (!admin)
> - goto done;
> + if (admin) {
Why did you invert this condition and introduced +1 indent level?
> + sched_nest =
> + nla_nest_start_noflag(skb, TCA_TAPRIO_ATTR_ADMIN_SCHED);
> + if (!sched_nest)
> + goto unlock;
>
> - sched_nest = nla_nest_start_noflag(skb, TCA_TAPRIO_ATTR_ADMIN_SCHED);
> - if (!sched_nest)
> - goto options_error;
> + if (dump_schedule(skb, admin)) {
> + nla_nest_cancel(skb, sched_nest);
The original code doesn't have nla_nest_cancel(), why was it added?
If it's needed, it would be good to make it a separate patch.
> + goto unlock;
> + }
>
> - if (dump_schedule(skb, admin))
> - goto admin_error;
> + nla_nest_end(skb, sched_nest);
> + }
>
> - nla_nest_end(skb, sched_nest);
> + rcu_read_unlock();
>
> -done:
> return nla_nest_end(skb, nest);
>
> -admin_error:
> - nla_nest_cancel(skb, sched_nest);
> +unlock:
> + rcu_read_unlock();
>
> options_error:
> nla_nest_cancel(skb, nest);
Thanks,
Olek
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