netdev - Re: [PATCH 6/6] net: Free skbs from irqs when possible.

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Thu, 27 Mar 2014 16:02:09 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	David Miller <davem@...emloft.net>
Cc:	stephen@...workplumber.org, eric.dumazet@...il.com,
	netdev@...r.kernel.org, xiyou.wangcong@...il.com, mpm@...enic.com,
	satyam.sharma@...il.com
Subject: Re: [PATCH 6/6] net: Free skbs from irqs when possible.

David Miller <davem@...emloft.net> writes:

> From: ebiederm@...ssion.com (Eric W. Biederman)
> Date: Tue, 18 Mar 2014 10:47:36 -0700
>
>> Most of the destructors today are fine (which doubly makes the warning
>> confusing).
>
> Not true by my estimation.  We absolutely do not want socket state being
> modified from hardware interrupts, and that's the most common destructor,
> releasing socket memory.

I definitely was not and am not suggesting that we change this.


I was just pointing out the difference between hard irq and soft irq
state for code is very slight, and I do not see anything that stands out
as hard irq unsafe.


Here is what I see when I read the destructors:

sock_rmem_free 
    is an antomic operation which is safe in all contexts.

sock_wfree
    appears safe in hard irq contect assuming the comment about
    of sk_free being safe in hard irq context is correct.

sock_rfree
    except for changing sk_foward_alloc without any kind of
    apparent serialization in sk_mem_uncharge appears safe.

sock_edemux 
    This just calls sock_put and inet_twsk_put
    sock_put just calls sk_put (which is documented as hard irq safe)
    Nothing in inet_twsk_put appears unsafe in hard irq context.

There are other destructors out there that definitely do things such
as call local_bh_disable that are unambiguously unsafe in hard irq
context but I had to look hard to find them.

Eric
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html