From: Al Viro <viro@ZenIV.linux.org.uk>
To: Cong Wang <xiyou.wangcong@gmail.com>
Cc: Jamal Hadi Salim <jhs@mojatatu.com>,
Kees Cook <keescook@chromium.org>,
LKML <linux-kernel@vger.kernel.org>,
Jiri Pirko <jiri@resnulli.us>, David Miller <davem@davemloft.net>,
Linux Kernel Network Developers <netdev@vger.kernel.org>
Subject: Re: [PATCH] net: sched: Fix memory exposure from short TCA_U32_SEL
Date: Tue, 28 Aug 2018 16:59:38 +0100 [thread overview]
Message-ID: <20180828155938.GF6515@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20180828000310.GE6515@ZenIV.linux.org.uk>
On Tue, Aug 28, 2018 at 01:03:10AM +0100, Al Viro wrote:
> if (tcf_exts_get_net(&n->exts))
> tcf_queue_work(&n->rwork, u32_delete_key_freepf_work);
> else
> u32_destroy_key(n->tp, n, true);
> ... and we hit u32_destroy_key(<tp>, <knode>, true), which does
Speaking of which, we'd better never hit that branch for other reasons - there's
no RCU delay between removal of knode from the hash chain and its kfree().
tcf_queue_work() does guarantee such delay (by use of queue_rcu_work()), direct
call doesn't...
Anyway, whichever branch is taken, the memory corruption problem remains - the
comments below are accurate, AFAICS.
> Incidentally, if we hit
> tcf_queue_work(&n->rwork, u32_delete_key_freepf_work);
> instead of u32_destroy_key(), the things don't seem to be any better - we
> won't do anything to <knode> until rtnl is dropped, so u32_destroy() won't
> break on the second pass through the loop - it'll free <ht0> there and
> return. Setting us up for trouble, since when u32_delete_key_freepf_work()
> finally gets to u32_destroy_key() we'll have <knode>->ht_down pointing
> to freed memory and decrementing its contents...
next prev parent reply other threads:[~2018-08-28 15:59 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-26 5:58 [PATCH] net: sched: Fix memory exposure from short TCA_U32_SEL Kees Cook
2018-08-26 6:15 ` Al Viro
2018-08-26 6:19 ` Kees Cook
2018-08-26 17:30 ` Jamal Hadi Salim
2018-08-26 21:56 ` Kees Cook
2018-08-27 11:46 ` Jamal Hadi Salim
2018-08-27 14:08 ` Kees Cook
2018-08-27 14:26 ` Roman Mashak
2018-08-26 17:32 ` Al Viro
2018-08-26 18:57 ` Joe Perches
2018-08-26 21:24 ` Al Viro
2018-08-26 22:26 ` Joe Perches
2018-08-26 22:43 ` Al Viro
2018-08-27 2:00 ` Julia Lawall
2018-08-27 2:35 ` Al Viro
2018-08-27 3:35 ` Julia Lawall
2018-08-27 4:04 ` Al Viro
2018-08-27 4:41 ` Julia Lawall
2018-08-27 1:59 ` Julia Lawall
2018-08-26 22:57 ` Al Viro
2018-08-27 11:57 ` Jamal Hadi Salim
2018-08-27 21:31 ` Cong Wang
2018-08-28 0:03 ` Al Viro
2018-08-28 15:59 ` Al Viro [this message]
2018-08-31 4:03 ` Al Viro
2018-08-29 19:07 ` Cong Wang
2018-08-29 21:33 ` Al Viro
2018-08-26 21:22 ` David Miller
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