Re: [PATCH] sanitize task->comm to avoid leaking escape codes

Oleg Nesterov
2010-06-23T19:44:06Z

On 06/23, Kees Cook wrote:
>
> @@ -956,7 +957,15 @@ void set_task_comm(struct task_struct *tsk, char *buf)
> */
> memset(tsk->comm, 0, TASK_COMM_LEN);
> wmb();

Off-topic. I'd wish I could understand this barrier. Since the lockless
reader doesn't do rmb() I don't see how this can help. OTOH, I don't
understand why it is needed, we never change ->comm[TASK_COMM_LEN-1] == '0'.

> - strlcpy(tsk->comm, buf, sizeof(tsk->comm));
> +
> + /* sanitize non-printable characters */
> + for (i = 0; buf[i] && i < (sizeof(tsk->comm) - 1); i++) {
> + if (!isprint(buf[i]))
> + tsk->comm[i] = '?';
> + else
> + tsk->comm[i] = buf[i];
> + }

Personally I think this makes sense.

> -extern char *get_task_comm(char *to, struct task_struct *tsk);
> +#define get_task_comm(buf, task) get_task_comm_size(buf, sizeof(buf), task)
> +extern char *get_task_comm_size(char *to, size_t len, struct task_struct *tsk);

Oh, but this means that get_task_comm(ptr, task) doesn't work?

Oleg.