linux-kernel - Re: [PATCH 2/2] x86/elf: remove the unnecessary ADDR_NO_RANDOMIZE checks in stack_maxrandom_size() and randomize_stack

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Message-ID: <7250417d-e0c7-7506-92b7-10e9088f5184@virtuozzo.com>
Date:   Mon, 10 Jul 2017 14:58:24 +0300
From:   Dmitry Safonov <dsafonov@...tuozzo.com>
To:     Oleg Nesterov <oleg@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     Andy Lutomirski <luto@...nel.org>, Borislav Petkov <bp@...e.de>,
        Cyrill Gorcunov <gorcunov@...nvz.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] x86/elf: remove the unnecessary ADDR_NO_RANDOMIZE
 checks in stack_maxrandom_size() and randomize_stack_top()

On 07/10/2017 02:14 PM, Oleg Nesterov wrote:
> PF_RANDOMIZE is set by load_elf_binary() only if ADDR_NO_RANDOMIZE is not
> set, no need to re-check after that.that.that.that.that.that.that.that.
> 
> Signed-off-by: Oleg Nesterov <oleg@...hat.com>

Reviewed-by: Dmitry Safonov <dsafonov@...tuozzo.com>

> ---
>   arch/x86/mm/mmap.c | 3 +--
>   fs/binfmt_elf.c    | 3 +--
>   2 files changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c
> index 6369d04..81db3e9 100644
> --- a/arch/x86/mm/mmap.c
> +++ b/arch/x86/mm/mmap.c
> @@ -50,8 +50,7 @@ unsigned long tasksize_64bit(void)
>   static unsigned long stack_maxrandom_size(unsigned long task_size)
>   {
>   	unsigned long max = 0;
> -	if ((current->flags & PF_RANDOMIZE) &&
> -		!(current->personality & ADDR_NO_RANDOMIZE)) {
> +	if (current->flags & PF_RANDOMIZE) {
>   		max = (-1UL) & __STACK_RND_MASK(task_size == tasksize_32bit());
>   		max <<= PAGE_SHIFT;
>   	}
> diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
> index 5075fd5..569c82e 100644
> --- a/fs/binfmt_elf.c
> +++ b/fs/binfmt_elf.c
> @@ -666,8 +666,7 @@ static unsigned long randomize_stack_top(unsigned long stack_top)
>   {
>   	unsigned long random_variable = 0;
>   
> -	if ((current->flags & PF_RANDOMIZE) &&
> -		!(current->personality & ADDR_NO_RANDOMIZE)) {
> +	if (current->flags & PF_RANDOMIZE) {
>   		random_variable = get_random_long();
>   		random_variable &= STACK_RND_MASK;
>   		random_variable <<= PAGE_SHIFT;
> 


-- 
              Dmitry