linux-kernel - Re: [PATCH 3.18 01/33] Revert "stackprotector: Increase the per-task stack canarys random range from 32 bits to 64 bits on 64-bit platforms"

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Date:   Mon, 5 Jun 2017 12:13:11 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        "# 3.4.x" <stable@...r.kernel.org>,
        Philip Müller <philm@...jaro.org>,
        Daniel Micay <danielmicay@...il.com>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        Rik van Riel <riel@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "kernel-hardening@...ts.openwall.com" 
        <kernel-hardening@...ts.openwall.com>,
        Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH 3.18 01/33] Revert "stackprotector: Increase the per-task
 stack canarys random range from 32 bits to 64 bits on 64-bit platforms"

On Mon, Jun 5, 2017 at 9:16 AM, Greg Kroah-Hartman
<gregkh@...uxfoundation.org> wrote:
> 3.18-stable review patch.  If anyone has any objections, please let me know.
>
> ------------------
>
> From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>
> This reverts commit 609a3e81550b0b4ea87197b0f59455a7bcff975a which is
> commit 5ea30e4e58040cfd6434c2f33dc3ea76e2c15b05 upstream.
>
> It shouldn't have been backported to 3.18, as we do not have
> get_random_long() in that kernel tree.

It should be possible to trivially backport
ec9ee4acd97c0039a61c0ae4f12705767ae62153 to gain get_random_long().

-Kees

>
> Reported-by: Philip Müller <philm@...jaro.org>
> Cc: Daniel Micay <danielmicay@...il.com>
> Cc: Arjan van de Ven <arjan@...ux.intel.com>
> Cc: Rik van Riel <riel@...hat.com>
> Cc: Kees Cook <keescook@...omium.org>
> Cc: Arjan van Ven <arjan@...ux.intel.com>
> Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: kernel-hardening@...ts.openwall.com
> Cc: Ingo Molnar <mingo@...nel.org>
> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>
> ---
>  kernel/fork.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -338,7 +338,7 @@ static struct task_struct *dup_task_stru
>         set_task_stack_end_magic(tsk);
>
>  #ifdef CONFIG_CC_STACKPROTECTOR
> -       tsk->stack_canary = get_random_long();
> +       tsk->stack_canary = get_random_int();
>  #endif
>
>         /*
>
>



-- 
Kees Cook
Pixel Security