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  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, 1 Jul 2020 14:48:02 -0400 (EDT)
From:   Mathieu Desnoyers <>
To:     Eric Dumazet <>
Cc:     "David S. Miller" <>,
        netdev <>,
        Eric Dumazet <>,
        Herbert Xu <>,
        Marco Elver <>
Subject: Re: [PATCH v2 net] tcp: md5: refine
 tcp_md5_do_add()/tcp_md5_hash_key() barriers

----- On Jul 1, 2020, at 2:43 PM, Eric Dumazet wrote:

> My prior fix went a bit too far, according to Herbert and Mathieu.
> Since we accept that concurrent TCP MD5 lookups might see inconsistent
> keys, we can use READ_ONCE()/WRITE_ONCE() instead of smp_rmb()/smp_wmb()
> Clearing all key->key[] is needed to avoid possible KMSAN reports,
> if key->keylen is increased. Since tcp_md5_do_add() is not fast path,
> using __GFP_ZERO to clear all struct tcp_md5sig_key is simpler.
> data_race() was added in linux-5.8 and will prevent KCSAN reports,
> this can safely be removed in stable backports, if data_race() is
> not yet backported.
> v2: use data_race() both in tcp_md5_hash_key() and tcp_md5_do_add()
> Fixes: 6a2febec338d ("tcp: md5: add missing memory barriers in
> tcp_md5_do_add()/tcp_md5_hash_key()")
> Signed-off-by: Eric Dumazet <>
> Cc: Mathieu Desnoyers <>

Reviewed-by: Mathieu Desnoyers <>

Thanks !


Mathieu Desnoyers
EfficiOS Inc.

Powered by blists - more mailing lists