Re: [PATCH 1/2] creds: kill __task_cred()->task_is_dead() check

[David Howells]

Oleg Nesterov <oleg@xxxxxxxxxx> wrote:

> From 8f92054e commit:
> 
>     Instead, add the following validation condition:
> 
>         task->exit_state >= 0
> 
>     to permit the access if the target task is dead and therefore unable to change
>     its own credentials.
> 
> OK, but afaics currently this can only help wait_task_zombie() which
> calls __task_cred() without rcu lock.
> 
> Remove this validation and change wait_task_zombie() to use task_uid()
> instead. This means we do rcu_read_lock() only to shut up the lockdep,
> but we already do the same in, say, wait_task_stopped().
> 
> Unfortunately, we can't kill task_is_dead() right now, it has already
> found the users in drivers/staging/, and I bet the usage is wrong.
> 
> Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>

Acked-by: David Howells <dhowells@xxxxxxxxxx>

It simplifies stuff in exchange for the most minor of slowdowns, so fair
enough.
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