linux-kernel - Re: [PATCH 2/2] block: fix ioprio_get/set(IOPRIO_WHO

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Date:   Mon, 17 Aug 2020 16:09:42 +0200
From:   Oleg Nesterov <oleg@...hat.com>
To:     Davidlohr Bueso <dave@...olabs.net>
Cc:     akpm@...ux-foundation.org, axboe@...nel.dk,
        linux-kernel@...r.kernel.org, Greg Thelen <gthelen@...gle.com>,
        Davidlohr Bueso <dbueso@...e.de>
Subject: Re: [PATCH 2/2] block: fix ioprio_get/set(IOPRIO_WHO_PGRP) vs
 setuid(2)

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@...hat.com>