Re: [PATCH 2/2] block: fix ioprio_get/set(IOPRIO_WHO_PGRP) vs setuid(2)

[Oleg Nesterov]

On 08/16, Davidlohr Bueso wrote:
>
> --- a/block/ioprio.c
> +++ b/block/ioprio.c
> @@ -119,11 +119,13 @@ SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio)
>  				pgrp = task_pgrp(current);
>  			else
>  				pgrp = find_vpid(who);
> +			read_lock(&tasklist_lock);
>  			do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
>  				ret = set_task_ioprio(p, ioprio);
>  				if (ret)
>  					break;
>  			} while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
> +			read_unlock(&tasklist_lock);
>  			break;
>  		case IOPRIO_WHO_USER:
>  			uid = make_kuid(current_user_ns(), who);
> @@ -207,6 +209,7 @@ SYSCALL_DEFINE2(ioprio_get, int, which, int, who)
>  				pgrp = task_pgrp(current);
>  			else
>  				pgrp = find_vpid(who);
> +			read_lock(&tasklist_lock);
>  			do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
>  				tmpio = get_task_ioprio(p);
>  				if (tmpio < 0)
> @@ -216,6 +219,7 @@ SYSCALL_DEFINE2(ioprio_get, int, which, int, who)
>  				else
>  					ret = ioprio_best(ret, tmpio);
>  			} while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
> +			read_unlock(&tasklist_lock);

Acked-by: Oleg Nesterov <oleg@xxxxxxxxxx>