linux-kernel - Re: [patch 2/4] Timerfd v2

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Message-ID: <4747B3F0.2020705@gmail.com>
Date:	Sat, 24 Nov 2007 06:17:36 +0100
From:	Michael Kerrisk <mtk.manpages@...glemail.com>
To:	Davide Libenzi <davidel@...ilserver.org>
CC:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Michael Kerrisk <mtk-manpages@....net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [patch 2/4] Timerfd v2 - new timerfd API

Hi Davide,

[...]

> +asmlinkage long sys_timerfd_create(int clockid, int flags)
>  {
> -	int error;
> +	int error, ufd;
>  	struct timerfd_ctx *ctx;
>  	struct file *file;
>  	struct inode *inode;
> -	struct itimerspec ktmr;
> -
> -	if (copy_from_user(&ktmr, utmr, sizeof(ktmr)))
> -		return -EFAULT;
>  
>  	if (clockid != CLOCK_MONOTONIC &&
>  	    clockid != CLOCK_REALTIME)
>  		return -EINVAL;

Could I suggest here, the following placeholder addition:

	if (flags != 0)
		return -EINVAL;

Later than can replaced with something like:

	if (flags & ~(O_NONBLOCK | O_CLOEXEC))
		return -EINVAL;

Having the first of the checks above will allow userland to determine what
is implemented, rather than having non-zero flags silently ignored.

Cheers,

Michael

> +	ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
> +	if (!ctx)
> +		return -ENOMEM;
> +
> +	init_waitqueue_head(&ctx->wqh);
> +	ctx->clockid = clockid;
> +	hrtimer_init(&ctx->tmr, clockid, HRTIMER_MODE_ABS);
> +
> +	error = anon_inode_getfd(&ufd, &inode, &file, "[timerfd]",
> +				 &timerfd_fops, ctx);
> +	if (error) {
> +		kfree(ctx);
> +		return error;
> +	}
> +
> +	return ufd;
> +}

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