Re: [PATCH 5/7] pid: Implement pid_nr

[Oleg Nesterov <oleg@tv-sign.ru>]

On 08/15, Eric W. Biederman wrote:
>
> +static inline pid_t pid_nr(struct pid *pid)
> +{
> +	pid_t nr = 0;
> +	if (pid)
> +		nr = pid->nr;
> +	return nr;
> +}

I think this is not safe, you need rcu locks here or the caller should
do some locking.

Let's look at f_getown() (PATCH 7/7). What if original task which was
pointed by ->f_owner.pid has gone, another thread does fcntl(F_SETOWN),
and pid_nr() takes a preemtion after 'if (pid)'? In this case 'pid->nr'
may follow a freed memory.

Oleg.

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/