linux-kernel - Re: [PATCH] ila_xlat: add missing hash secret initialization

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Message-ID: <CALx6S355af1b7xKtu82yowy2_=4qyjWXgDP2ZmoF_9x1Wvj_yA@mail.gmail.com>
Date:   Thu, 8 Jun 2017 13:18:15 -0700
From:   Tom Herbert <tom@...bertland.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        James Morris <jmorris@...ei.org>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Patrick McHardy <kaber@...sh.net>,
        stephen hemminger <stephen@...workplumber.org>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ila_xlat: add missing hash secret initialization

On Thu, Jun 8, 2017 at 12:54 AM, Arnd Bergmann <arnd@...db.de> wrote:
> While discussing the possible merits of clang warning about unused initialized
> functions, I found one function that was clearly meant to be called but
> never actually is.
>
> __ila_hash_secret_init() initializes the hash value for the ila locator,
> apparently this is intended to prevent hash collision attacks, but this ends
> up being a read-only zero constant since there is no caller. I could find
> no indication of why it was never called, the earliest patch submission
> for the module already was like this. If my interpretation is right, we
> certainly want to backport the patch to stable kernels as well.
>
> I considered adding it to the ila_xlat_init callback, but for best effect
> the random data is read as late as possible, just before it is first used.
> The underlying net_get_random_once() is already highly optimized to avoid
> overhead when called frequently.
>
> Fixes: 7f00feaf1076 ("ila: Add generic ILA translation facility")
> Cc: stable@...r.kernel.org
> Link: https://www.spinics.net/lists/kernel/msg2527243.html
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  net/ipv6/ila/ila_xlat.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/net/ipv6/ila/ila_xlat.c b/net/ipv6/ila/ila_xlat.c
> index 2fd5ca151dcf..77f7f8c7d93d 100644
> --- a/net/ipv6/ila/ila_xlat.c
> +++ b/net/ipv6/ila/ila_xlat.c
> @@ -62,6 +62,7 @@ static inline u32 ila_locator_hash(struct ila_locator loc)
>  {
>         u32 *v = (u32 *)loc.v32;
>
> +       __ila_hash_secret_init();
>         return jhash_2words(v[0], v[1], hashrnd);
>  }
>
> --
> 2.9.0
>

Thanks Arnd!

Acked-by: Tom Herbert <tom@...bertland.com>