Subject: Re: [PATCH net-next v4 07/17] net: sched: protect filter_chain list with filter_chain_lock mutex

From: Ido Schimmel <[email-masked]>
Date: Thu, 14 Feb 2019 20:24:42 +0200

On Mon, Feb 11, 2019 at 10:55:38AM +0200, Vlad Buslov wrote:
> Extend tcf_chain with new filter_chain_lock mutex. Always lock the chain
> when accessing filter_chain list, instead of relying on rtnl lock.
> Dereference filter_chain with tcf_chain_dereference() lockdep macro to
> verify that all users of chain_list have the lock taken.
> 
> Rearrange tp insert/remove code in tc_new_tfilter/tc_del_tfilter to execute
> all necessary code while holding chain lock in order to prevent
> invalidation of chain_info structure by potential concurrent change. This
> also serializes calls to tcf_chain0_head_change(), which allows head change
> callbacks to rely on filter_chain_lock for synchronization instead of rtnl
> mutex.
> 
> Signed-off-by: Vlad Buslov <[email-masked]>
> Acked-by: Jiri Pirko <[email-masked]>

With this sequence [1] I get the following trace [2]. Bisected it to
this patch. Note that second filter is rejected by the device driver
(that's the intention). I guess it is not properly removed from the
filter chain in the error path?

Thanks

[1]
# tc qdisc add dev swp3 clsact
# tc filter add dev swp3 ingress pref 1 matchall skip_sw \
	action mirred egress mirror dev swp7
# tc filter add dev swp3 ingress pref 2 matchall skip_sw \
	action mirred egress mirror dev swp7
RTNETLINK answers: File exists
We have an error talking to the kernel, -1
# tc qdisc del dev swp3 clsact

[2]
[   70.545131] kasan: GPF could be caused by NULL-ptr deref or user memory access
[   70.553394] general protection fault: 0000 [#1] PREEMPT SMP KASAN PTI
[   70.560618] CPU: 2 PID: 2268 Comm: tc Not tainted 5.0.0-rc5-custom-02103-g415d39427317 #1304
[   70.570065] Hardware name: Mellanox Technologies Ltd. MSN2100-CB2FO/SA001017, BIOS 5.6.5 06/07/2016
[   70.580204] RIP: 0010:mall_reoffload+0x14a/0x760
[   70.585382] Code: c1 0f 85 ba 05 00 00 31 c0 4d 8d 6c 24 34 b9 06 00 00 00 4c 89 ff f3 48 ab 4c 89 ea 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 <0f> b6 14 02 4c 89 e8 83
e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 bd
[   70.606382] RSP: 0018:ffff888231faefc0 EFLAGS: 00010207
[   70.612235] RAX: dffffc0000000000 RBX: 1ffff110463f5dfe RCX: 0000000000000000
[   70.620220] RDX: 0000000000000006 RSI: 1ffff110463f5e01 RDI: ffff888231faf040
[   70.628206] RBP: ffff8881ef151a00 R08: 0000000000000000 R09: ffffed10463f5dfa
[   70.636192] R10: ffffed10463f5dfa R11: 0000000000000003 R12: 0000000000000000
[   70.644177] R13: 0000000000000034 R14: 0000000000000000 R15: ffff888231faf010
[   70.652163] FS:  00007f46b5bf0800(0000) GS:ffff888236c00000(0000) knlGS:0000000000000000
[   70.661218] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   70.667649] CR2: 0000000001d590a8 CR3: 0000000231c3c000 CR4: 00000000001006e0
[   70.675633] Call Trace:
[   70.693046]  tcf_block_playback_offloads+0x94/0x230
[   70.710617]  __tcf_block_cb_unregister+0xf7/0x2d0
[   70.734143]  mlxsw_sp_setup_tc+0x20f/0x660
[   70.738739]  tcf_block_offload_unbind+0x22b/0x350
[   70.748898]  __tcf_block_put+0x203/0x630
[   70.769700]  tcf_block_put_ext+0x2f/0x40
[   70.774098]  clsact_destroy+0x7a/0xb0
[   70.782604]  qdisc_destroy+0x11a/0x5c0
[   70.786810]  qdisc_put+0x5a/0x70
[   70.790435]  notify_and_destroy+0x8e/0xa0
[   70.794933]  qdisc_graft+0xbb7/0xef0
[   70.809009]  tc_get_qdisc+0x518/0xa30
[   70.821530]  rtnetlink_rcv_msg+0x397/0xa20
[   70.835510]  netlink_rcv_skb+0x132/0x380
[   70.848419]  netlink_unicast+0x4c0/0x690
[   70.866019]  netlink_sendmsg+0x929/0xe10
[   70.882134]  sock_sendmsg+0xc8/0x110
[   70.886144]  ___sys_sendmsg+0x77a/0x8f0
[   70.924064]  __sys_sendmsg+0xf7/0x250
[   70.955727]  do_syscall_64+0x14d/0x610