netdev - Re: [PATCH net v2] cls_flower: fix use after free in flower S/W path

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Date:   Thu, 21 Jun 2018 20:16:50 +0200
From:   Jiri Pirko <jiri@...nulli.us>
To:     Paolo Abeni <pabeni@...hat.com>
Cc:     netdev@...r.kernel.org, Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        Paul Blakey <paulb@...lanox.com>
Subject: Re: [PATCH net v2] cls_flower: fix use after free in flower S/W path

Thu, Jun 21, 2018 at 08:02:16PM CEST, pabeni@...hat.com wrote:
>If flower filter is created without the skip_sw flag, fl_mask_put()
>can race with fl_classify() and we can destroy the mask rhashtable
>while a lookup operation is accessing it.
>
> BUG: unable to handle kernel paging request at 00000000000911d1
> PGD 0 P4D 0
> SMP PTI
> CPU: 3 PID: 5582 Comm: vhost-5541 Not tainted 4.18.0-rc1.vanilla+ #1950
> Hardware name: Dell Inc. PowerEdge R730/072T6D, BIOS 2.1.7 06/16/2016
> RIP: 0010:rht_bucket_nested+0x20/0x60
> Code: 31 c8 c1 c1 18 29 c8 c3 66 90 8b 4f 04 ba 01 00 00 00 8b 07 48 8b bf 80 00 00 0
> RSP: 0018:ffffafc5cfbb7a48 EFLAGS: 00010206
> RAX: 0000000000001978 RBX: ffff9f12dff88a00 RCX: 00000000ffff9f12
> RDX: 00000000000911d1 RSI: 0000000000000148 RDI: 0000000000000001
> RBP: ffff9f12dff88a00 R08: 000000005f1cc119 R09: 00000000a715fae2
> R10: ffffafc5cfbb7aa8 R11: ffff9f1cb4be804e R12: ffff9f1265e13000
> R13: 0000000000000000 R14: ffffafc5cfbb7b48 R15: ffff9f12dff88b68
> FS:  0000000000000000(0000) GS:ffff9f1d3f0c0000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00000000000911d1 CR3: 0000001575a94006 CR4: 00000000001626e0
> Call Trace:
>  fl_lookup+0x134/0x140 [cls_flower]
>  fl_classify+0xf3/0x180 [cls_flower]
>  tcf_classify+0x78/0x150
>  __netif_receive_skb_core+0x69e/0xa50
>  netif_receive_skb_internal+0x42/0xf0
>  tun_get_user+0xdd5/0xfd0 [tun]
>  tun_sendmsg+0x52/0x70 [tun]
>  handle_tx+0x2b3/0x5f0 [vhost_net]
>  vhost_worker+0xab/0x100 [vhost]
>  kthread+0xf8/0x130
>  ret_from_fork+0x35/0x40
> Modules linked in: act_mirred act_gact cls_flower vhost_net vhost tap sch_ingress
> CR2: 00000000000911d1
>
>Fix the above waiting for a RCU grace period before destroying the
>rhashtable: we need to use tcf_queue_work(), as rhashtable_destroy()
>must run in process context, as pointed out by Cong Wang.
>
>v1 -> v2: use tcf_queue_work to run rhashtable_destroy().
>
>Fixes: 05cd271fd61a ("cls_flower: Support multiple masks per priority")
>Signed-off-by: Paolo Abeni <pabeni@...hat.com>

Acked-by: Jiri Pirko <jiri@...lanox.com>