Message-ID: <1448558959.24696.91.camel@edumazet-glaptop2.roam.corp.google.com>
Subject: Re: use-after-free in sock_wake_async
From: Eric Dumazet <eric.dumazet@gmail.com>
To: Hannes Frederic Sowa <hannes@stressinduktion.org>
Cc: Rainer Weikusat <rweikusat@mobileactivedefense.com>,
        Eric Dumazet <edumazet@google.com>, Dmitry Vyukov <dvyukov@google.com>,
        Benjamin LaHaise <bcrl@kvack.org>,
        "David S. Miller" <davem@davemloft.net>,
        Al Viro <viro@zeniv.linux.org.uk>, David Howells <dhowells@redhat.com>,
        Ying Xue <ying.xue@windriver.com>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        netdev <netdev@vger.kernel.org>, LKML <linux-kernel@vger.kernel.org>,
        syzkaller <syzkaller@googlegroups.com>,
        Kostya Serebryany <kcc@google.com>,
        Alexander Potapenko <glider@google.com>,
        Sasha Levin <sasha.levin@oracle.com>
Date: Thu, 26 Nov 2015 09:29:19 -0800
In-Reply-To: <1448557398.912656.450874953.4CA824F0@webmail.messagingengine.com>
References: <CACT4Y+ZZQ0ooT9LekV35u_jUAtAHJfg5O5SD=xATfHUF5UdNBQ@mail.gmail.com>
	 <CANn89i+Uw+YzhRbQVSyf=FAQBO06JfFoxQpSHxfmDpS5_iZBQw@mail.gmail.com>
	 <87poyzj7j2.fsf@doppelsaurus.mobileactivedefense.com>
	 <CANn89iKg0Lc7OVLhxUOzPRr4OhEGxA8L7V1jyaqFAS6+7kEXTA@mail.gmail.com>
	 <87io4qevdp.fsf@doppelsaurus.mobileactivedefense.com>
	 <CANn89iJgW+6giMUicU1m831+mkaNy9z1hQB-ixvRHBqZo-7Yig@mail.gmail.com>
	 <87io4q3u8u.fsf@doppelsaurus.mobileactivedefense.com>
	 <1448471494.24696.18.camel@edumazet-glaptop2.roam.corp.google.com>
	 <87a8q23s2a.fsf@doppelsaurus.mobileactivedefense.com>
	 <1448473891.24696.21.camel@edumazet-glaptop2.roam.corp.google.com>
	 <87610q3pjg.fsf@doppelsaurus.mobileactivedefense.com>
	 <1448476744.24696.25.camel@edumazet-glaptop2.roam.corp.google.com>
	 <87y4dl3m5c.fsf@doppelsaurus.mobileactivedefense.com>
	 <1448481002.24696.30.camel@edumazet-glaptop2.roam.corp.google.com>
	 <1448483017.24696.33.camel@edumazet-glaptop2.roam.corp.google.com>
	 <87two93ig8.fsf@doppelsaurus.mobileactivedefense.com>
	 <1448489350.24696.47.camel@edumazet-glaptop2.roam.corp.google.com>
	 <1448490732.1842763.450231537.5358AF37@webmail.messagingengine.com>
	 <1448491414.24696.60.camel@edumazet-glaptop2.roam.corp.google.com>
	 <1448491950.1848115.450243417.726E2DCB@webmail.messagingengine.com>
	 <87r3jcx4w7.fsf@stressinduktion.org>
	 <1448553090.24696.71.camel@edumazet-glaptop2.roam.corp.google.com>
	 <1448557398.912656.450874953.4CA824F0@webmail.messagingengine.com>
Content-Type: text/plain; charset="UTF-8"
Mime-Version: 1.0
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 923
Lines: 23

On Thu, 2015-11-26 at 18:03 +0100, Hannes Frederic Sowa wrote:

> Also isn't the reason why slub exists so it can track memory regions
> per-cpu.

call_rcu() and kfree_rcu() will add a grace period (multiple ms) where
the cpu will likely evict from its caches the data contained in the
'about to be freed' objects, defeating the SLUB/SLAB ability to quickly
reuse a freed and hot object (LIFO)

This is one of the major RCU drawback : Force a FIFO behavior in object
reuse while LIFO one is much better for data locality, especially with
per-cpu lists.

Another problem is a slightly bigger working set size, which can hurt
some workloads that used to exactly fit cpu caches.


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/