netdev - Re: TCP-MD5 checksum failure on x86

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Date:	Fri, 07 May 2010 07:32:09 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	bhaskie@...il.com, shemminger@...tta.com,
	bhutchings@...arflare.com, netdev@...r.kernel.org
Subject: Re: TCP-MD5 checksum failure on x86_64 SMP

Le jeudi 06 mai 2010 à 22:04 -0700, David Miller a écrit :
> From: Eric Dumazet <eric.dumazet@...il.com>

> > This code should be completely rewritten for linux-2.6.35, its very ugly
> > and over complex, yet it is not scalable.
> > 
> > It could use true percpu data, with no central lock or refcount.
> 
> Yes I've always disliked the way the TCP MD5 pool stuff is coded, it's
> frankly crap and this is like the 5th major bug that had to get fixed
> in it. :-)
> 
> But let's fix this as simply as possible in net-2.6 and -stable, so Eric
> let me know when you have a tested patch for me to apply.

There are so many things ...

I am comtemplating commit aa133076

__tcp_alloc_md5sig_pool() now do a : 

p = kzalloc(sizeof(*p), sk->sk_allocation);

But later call :

hash = crypto_alloc_hash("md5", 0, CRYPTO_ALG_ASYNC);

(GFP_KERNEL allocations for sure)


tcp_v4_parse_md5_keys() also use :

p = kzalloc(sizeof(*p), sk->sk_allocation);

right after a (possibly sleeping) copy_from_user()

Oh well...


I'll test the already suggested patch before official submission,
thanks.



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