Re: [PATCH] exec: Copy oldsighand->action under spin-lock

[Kees Cook]

On Mon, Jun 07, 2021 at 03:54:27PM +0200, Bernd Edlinger wrote:
> unshare_sighand should only access oldsighand->action
> while holding oldsighand->siglock, to make sure that
> newsighand->action is in a consistent state.
> 
> Signed-off-by: Bernd Edlinger <bernd.edlinger@xxxxxxxxxx>
> ---
>  fs/exec.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/exec.c b/fs/exec.c
> index d8af85f..8344fba 100644
> --- a/fs/exec.c
> +++ b/fs/exec.c
> @@ -1193,11 +1193,11 @@ static int unshare_sighand(struct task_struct *me)
>  			return -ENOMEM;
>  
>  		refcount_set(&newsighand->count, 1);
> -		memcpy(newsighand->action, oldsighand->action,
> -		       sizeof(newsighand->action));
>  
>  		write_lock_irq(&tasklist_lock);
>  		spin_lock(&oldsighand->siglock);
> +		memcpy(newsighand->action, oldsighand->action,
> +		       sizeof(newsighand->action));
>  		rcu_assign_pointer(me->sighand, newsighand);
>  		spin_unlock(&oldsighand->siglock);
>  		write_unlock_irq(&tasklist_lock);

Oh, yeah, that's a nice catch.

Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>

-- 
Kees Cook