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Date: Thu, 17 Sep 2015 14:29:26 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: bsegall@google.com
Cc: linux-kernel@vger.kernel.org, Oleg Nesterov <oleg@redhat.com>,
        Al Viro <viro@zeniv.linux.org.uk>,
        "Eric W. Biederman" <ebiederm@xmission.com>
Subject: Re: [PATCH] pidns: fix set/getpriority and ioprio_set/get in
 PRIO_USER mode
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On Wed, 16 Sep 2015 12:58:04 -0700 bsegall@google.com wrote:

> setpriority(PRIO_USER, 0, x) will change the priority of tasks outside
> of the current pid namespace. This is in contrast to both the other
> modes of setpriority and the example of kill(-1). Fix this. getpriority
> and ioprio have the same failure mode, fix them too.

(cc Eric)

> Signed-off-by: Ben Segall <bsegall@google.com>
> Cc: Oleg Nesterov <oleg@redhat.com>
> Cc: Al Viro <viro@zeniv.linux.org.uk>
> ---
>  block/ioprio.c | 6 ++++--
>  kernel/sys.c   | 4 ++--
>  2 files changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/block/ioprio.c b/block/ioprio.c
> index 31666c9..cc7800e 100644
> --- a/block/ioprio.c
> +++ b/block/ioprio.c
> @@ -123,7 +123,8 @@ SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio)
>  				break;
>  
>  			do_each_thread(g, p) {
> -				if (!uid_eq(task_uid(p), uid))
> +				if (!uid_eq(task_uid(p), uid) ||
> +				    !task_pid_vnr(p))
>  					continue;
>  				ret = set_task_ioprio(p, ioprio);
>  				if (ret)
> @@ -220,7 +221,8 @@ SYSCALL_DEFINE2(ioprio_get, int, which, int, who)
>  				break;
>  
>  			do_each_thread(g, p) {
> -				if (!uid_eq(task_uid(p), user->uid))
> +				if (!uid_eq(task_uid(p), user->uid) ||
> +				    !task_pid_vnr(p))
>  					continue;
>  				tmpio = get_task_ioprio(p);
>  				if (tmpio < 0)
> diff --git a/kernel/sys.c b/kernel/sys.c
> index fa2f2f6..6af9212 100644
> --- a/kernel/sys.c
> +++ b/kernel/sys.c
> @@ -222,7 +222,7 @@ SYSCALL_DEFINE3(setpriority, int, which, int, who, int, niceval)
>  				goto out_unlock;	/* No processes for this user */
>  		}
>  		do_each_thread(g, p) {
> -			if (uid_eq(task_uid(p), uid))
> +			if (uid_eq(task_uid(p), uid) && task_pid_vnr(p))
>  				error = set_one_prio(p, niceval, error);
>  		} while_each_thread(g, p);
>  		if (!uid_eq(uid, cred->uid))
> @@ -290,7 +290,7 @@ SYSCALL_DEFINE2(getpriority, int, which, int, who)
>  				goto out_unlock;	/* No processes for this user */
>  		}
>  		do_each_thread(g, p) {
> -			if (uid_eq(task_uid(p), uid)) {
> +			if (uid_eq(task_uid(p), uid) && task_pid_vnr(p)) {
>  				niceval = nice_to_rlimit(task_nice(p));
>  				if (niceval > retval)
>  					retval = niceval;
> -- 
> 2.6.0.rc0.131.gf624c3d
> 
> --
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