Re: [PATCH 2/2] x86/elf: remove the unnecessary ADDR_NO_RANDOMIZE checks in stack_maxrandom_size() and randomize_stack_top()

Dmitry Safonov
2017-07-10T11:58:52Z

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@redhat.com>

Reviewed-by: Dmitry Safonov <dsafonov@virtuozzo.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