netdev - Re: [RFC] tcp md5 use of alloc

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:	Wed, 22 Oct 2014 22:23:53 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Ahern <dsahern@...il.com>
Cc:	Crestez Dan Leonard <cdleonard@...il.com>, netdev@...r.kernel.org
Subject: Re: [RFC] tcp md5 use of alloc_percpu

On Wed, 2014-10-22 at 22:40 -0600, David Ahern wrote:
> On 10/22/14, 12:55 PM, Crestez Dan Leonard wrote:
> > Hello,
> >
> > It seems that the TCP MD5 feature allocates a percpu struct tcp_md5sig_pool and uses part of that memory for a scratch buffer to do crypto on. Here is the relevant code:
> 
> This is a forward port of a local change to address the problem (local 
> kernel version is 3.4 so perhaps my quick bump to top of tree is off but 
> it shows the general idea). Been on my to-do list to figure out why this 
> is needed, but it seems related to your problem:
> 
> diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
> index 1bec4e76d88c..833a676bd4b0 100644
> --- a/net/ipv4/tcp.c
> +++ b/net/ipv4/tcp.c
> @@ -2941,7 +2941,7 @@ struct tcp_md5sig_pool *tcp_get_md5sig_pool(void)
>      local_bh_disable();
>      p = ACCESS_ONCE(tcp_md5sig_pool);
>      if (p)
> -       return raw_cpu_ptr(p);
> +       return __va(per_cpu_ptr_to_phys(raw_cpu_ptr(p)));
> 
>      local_bh_enable();
>      return NULL;

per_cpu_ptr_to_phys() can be pretty expensive and should not be called
in fast path.


--
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