netdev - Re: [patch net-next] net: sched: fix use-after-free in tcf_block_put

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Message-ID: <CAM_iQpXAYvvn0t6QGo0eSAGJJg_mMF5oWef7rvXE-H0BwxPt0w@mail.gmail.com>
Date:   Fri, 8 Dec 2017 12:05:47 -0800
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Jiri Pirko <jiri@...nulli.us>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>,
        David Miller <davem@...emloft.net>,
        Jamal Hadi Salim <jhs@...atatu.com>, mlxsw@...lanox.com,
        Roman Kapl <code@...pl.cz>
Subject: Re: [patch net-next] net: sched: fix use-after-free in tcf_block_put_ext

On Fri, Dec 8, 2017 at 10:27 AM, Jiri Pirko <jiri@...nulli.us> wrote:
> From: Jiri Pirko <jiri@...lanox.com>
>
> Since the block is freed with last chain being put, once we reach the
> end of iteration of list_for_each_entry_safe, the block may be
> already freed. I'm hitting this only by creating and deleting clsact:

List is still too tricky to work with refcnt.

>
> [  202.171952] ==================================================================
> [  202.180182] BUG: KASAN: use-after-free in tcf_block_put_ext+0x240/0x390


I should enable KASAN now, otherwise can't catch this
even though I tested this code path for hundreds of times.