netdev - Re: [PATCH net 1/2] net: sched: police: allow accessing police->params with rtnl

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Date:   Mon, 5 Aug 2019 12:38:26 +0100
From:   Pieter Jansen van Vuuren <pieter.jansenvanvuuren@...ronome.com>
To:     Vlad Buslov <vladbu@...lanox.com>, netdev@...r.kernel.org
Cc:     jhs@...atatu.com, xiyou.wangcong@...il.com, jiri@...nulli.us,
        davem@...emloft.net
Subject: Re: [PATCH net 1/2] net: sched: police: allow accessing
 police->params with rtnl

On 2019/08/03 14:36, Vlad Buslov wrote:
> Recently implemented support for police action in flow_offload infra leads
> to following rcu usage warning:
> 
> [ 1925.881092] =============================
> [ 1925.881094] WARNING: suspicious RCU usage
> [ 1925.881098] 5.3.0-rc1+ #574 Not tainted
> [ 1925.881100] -----------------------------
> [ 1925.881104] include/net/tc_act/tc_police.h:57 suspicious rcu_dereference_check() usage!
> [ 1925.881106]
>                other info that might help us debug this:
> 
> [ 1925.881109]
>                rcu_scheduler_active = 2, debug_locks = 1
> [ 1925.881112] 1 lock held by tc/18591:
> [ 1925.881115]  #0: 00000000b03cb918 (rtnl_mutex){+.+.}, at: tc_new_tfilter+0x47c/0x970
> [ 1925.881124]
>                stack backtrace:
> [ 1925.881127] CPU: 2 PID: 18591 Comm: tc Not tainted 5.3.0-rc1+ #574
> [ 1925.881130] Hardware name: Supermicro SYS-2028TP-DECR/X10DRT-P, BIOS 2.0b 03/30/2017
> [ 1925.881132] Call Trace:
> [ 1925.881138]  dump_stack+0x85/0xc0
> [ 1925.881145]  tc_setup_flow_action+0x1771/0x2040
> [ 1925.881155]  fl_hw_replace_filter+0x11f/0x2e0 [cls_flower]
> [ 1925.881175]  fl_change+0xd24/0x1b30 [cls_flower]
> [ 1925.881200]  tc_new_tfilter+0x3e0/0x970
> [ 1925.881231]  ? tc_del_tfilter+0x720/0x720
> [ 1925.881243]  rtnetlink_rcv_msg+0x389/0x4b0
> [ 1925.881250]  ? netlink_deliver_tap+0x95/0x400
> [ 1925.881257]  ? rtnl_dellink+0x2d0/0x2d0
> [ 1925.881264]  netlink_rcv_skb+0x49/0x110
> [ 1925.881275]  netlink_unicast+0x171/0x200
> [ 1925.881284]  netlink_sendmsg+0x224/0x3f0
> [ 1925.881299]  sock_sendmsg+0x5e/0x60
> [ 1925.881305]  ___sys_sendmsg+0x2ae/0x330
> [ 1925.881309]  ? task_work_add+0x43/0x50
> [ 1925.881314]  ? fput_many+0x45/0x80
> [ 1925.881329]  ? __lock_acquire+0x248/0x1930
> [ 1925.881342]  ? find_held_lock+0x2b/0x80
> [ 1925.881347]  ? task_work_run+0x7b/0xd0
> [ 1925.881359]  __sys_sendmsg+0x59/0xa0
> [ 1925.881375]  do_syscall_64+0x5c/0xb0
> [ 1925.881381]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> [ 1925.881384] RIP: 0033:0x7feb245047b8
> [ 1925.881388] Code: 89 02 48 c7 c0 ff ff ff ff eb bb 0f 1f 80 00 00 00 00 f3 0f 1e fa 48 8d 05 65 8f 0c 00 8b 00 85 c0 75 17 b8 2e 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 58 c3 0f 1f 80 00 00 00 00 48 83
>  ec 28 89 54
> [ 1925.881391] RSP: 002b:00007ffc2d2a5788 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
> [ 1925.881395] RAX: ffffffffffffffda RBX: 000000005d4497ed RCX: 00007feb245047b8
> [ 1925.881398] RDX: 0000000000000000 RSI: 00007ffc2d2a57f0 RDI: 0000000000000003
> [ 1925.881400] RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000006
> [ 1925.881403] R10: 0000000000404ec2 R11: 0000000000000246 R12: 0000000000000001
> [ 1925.881406] R13: 0000000000480640 R14: 0000000000000012 R15: 0000000000000001
> 
> Change tcf_police_rate_bytes_ps() and tcf_police_tcfp_burst() helpers to
> allow using them from both rtnl and rcu protected contexts.
> 
> Fixes: 8c8cfc6ed274 ("net/sched: add police action to the hardware intermediate representation")
> Signed-off-by: Vlad Buslov <vladbu@...lanox.com>

Thank you Vlad.
Reviewed-by: Pieter Jansen van Vuuren <pieter.jansenvanvuuren@...ronome.com>