linux-kernel - Re: [kernel-hardening] [PATCH 4.4 47/90] 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, 12 Jun 2017 17:41:34 +0200
From:   Jann Horn <jannh@...gle.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     kernel list <linux-kernel@...r.kernel.org>, stable@...r.kernel.org,
        Daniel Micay <danielmicay@...il.com>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        Rik van Riel <riel@...hat.com>,
        Kees Cook <keescook@...omium.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Kernel Hardening <kernel-hardening@...ts.openwall.com>,
        Ingo Molnar <mingo@...nel.org>
Subject: Re: [kernel-hardening] [PATCH 4.4 47/90] stackprotector: Increase the
 per-task stack canarys random range from 32 bits to 64 bits on 64-bit platforms

AFAICS get_random_long() doesn't exist in 4.4 (except in
arch/x86/boot/compressed/aslr.c)? IIRC the same problem already
occured with another kernel version?

On Mon, Jun 12, 2017 at 5:25 PM, Greg Kroah-Hartman
<gregkh@...uxfoundation.org> wrote:
> 4.4-stable review patch.  If anyone has any objections, please let me know.
>
> ------------------
>
> From: Daniel Micay <danielmicay@...il.com>
>
> commit 5ea30e4e58040cfd6434c2f33dc3ea76e2c15b05 upstream.
>
> The stack canary is an 'unsigned long' and should be fully initialized to
> random data rather than only 32 bits of random data.
>
> Signed-off-by: Daniel Micay <danielmicay@...il.com>
> Acked-by: Arjan van de Ven <arjan@...ux.intel.com>
> Acked-by: Rik van Riel <riel@...hat.com>
> Acked-by: 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: stable@...r.kernel.org
> Link: http://lkml.kernel.org/r/20170504133209.3053-1-danielmicay@gmail.com
> Signed-off-by: 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
> @@ -368,7 +368,7 @@ static struct task_struct *dup_task_stru
>         set_task_stack_end_magic(tsk);
>
>  #ifdef CONFIG_CC_STACKPROTECTOR
> -       tsk->stack_canary = get_random_int();
> +       tsk->stack_canary = get_random_long();
>  #endif
>
>         /*
>
>