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From:   Jeff Moyer <jmoyer@redhat.com>
To:     adam.manzanares@wdc.com
Cc:     viro@zeniv.linux.org.uk, linux-fsdevel@vger.kernel.org,
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        linux-kernel@vger.kernel.org, linux-aio@kvack.org,
        linux-api@vger.kernel.org, hch@infradead.org
Subject: Re: [PATCH v5 1/5] block: add ioprio_check_cap function
In-Reply-To: <20180521160147.2372-2-adam.manzanares@wdc.com> (adam
        manzanares's message of "Mon, 21 May 2018 09:01:43 -0700")
References: <20180521160147.2372-1-adam.manzanares@wdc.com>
        <20180521160147.2372-2-adam.manzanares@wdc.com>
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Date:   Mon, 21 May 2018 16:58:14 -0400
Message-ID: <x49a7ssvi8p.fsf@segfault.boston.devel.redhat.com>
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adam.manzanares@wdc.com writes:

> From: Adam Manzanares <adam.manzanares@wdc.com>
>
> Aio per command iopriority support introduces a second interface between
> userland and the kernel capable of passing iopriority. The aio interface also
> needs the ability to verify that the submitting context has sufficient
> priviledges to submit IOPRIO_RT commands. This patch creates the
> ioprio_check_cap function to be used by the ioprio_set system call and also by
> the aio interface.
>
> Signed-off-by: Adam Manzanares <adam.manzanares@wdc.com>
> Reviewed-by: Christoph Hellwig <hch@lst.de>

Reviewed-by: Jeff Moyer <jmoyer@redhat.com>


> ---
>  block/ioprio.c         | 22 ++++++++++++++++------
>  include/linux/ioprio.h |  2 ++
>  2 files changed, 18 insertions(+), 6 deletions(-)
>
> diff --git a/block/ioprio.c b/block/ioprio.c
> index 6f5d0b6625e3..f9821080c92c 100644
> --- a/block/ioprio.c
> +++ b/block/ioprio.c
> @@ -61,15 +61,10 @@ int set_task_ioprio(struct task_struct *task, int ioprio)
>  }
>  EXPORT_SYMBOL_GPL(set_task_ioprio);
>  
> -SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio)
> +int ioprio_check_cap(int ioprio)
>  {
>  	int class = IOPRIO_PRIO_CLASS(ioprio);
>  	int data = IOPRIO_PRIO_DATA(ioprio);
> -	struct task_struct *p, *g;
> -	struct user_struct *user;
> -	struct pid *pgrp;
> -	kuid_t uid;
> -	int ret;
>  
>  	switch (class) {
>  		case IOPRIO_CLASS_RT:
> @@ -92,6 +87,21 @@ SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio)
>  			return -EINVAL;
>  	}
>  
> +	return 0;
> +}
> +
> +SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio)
> +{
> +	struct task_struct *p, *g;
> +	struct user_struct *user;
> +	struct pid *pgrp;
> +	kuid_t uid;
> +	int ret;
> +
> +	ret = ioprio_check_cap(ioprio);
> +	if (ret)
> +		return ret;
> +
>  	ret = -ESRCH;
>  	rcu_read_lock();
>  	switch (which) {
> diff --git a/include/linux/ioprio.h b/include/linux/ioprio.h
> index 627efac73e6d..4a28cec49ec3 100644
> --- a/include/linux/ioprio.h
> +++ b/include/linux/ioprio.h
> @@ -77,4 +77,6 @@ extern int ioprio_best(unsigned short aprio, unsigned short bprio);
>  
>  extern int set_task_ioprio(struct task_struct *task, int ioprio);
>  
> +extern int ioprio_check_cap(int ioprio);
> +
>  #endif