linux-kernel - Re: [PATCH v2 21/29] nios2: Futex operations

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Date:	Tue, 15 Jul 2014 12:03:28 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Ley Foon Tan <lftan@...era.com>
cc:	linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-doc@...r.kernel.org, lftan.linux@...il.com,
	cltang@...esourcery.com
Subject: Re: [PATCH v2 21/29] nios2: Futex operations

On Tue, 15 Jul 2014, Ley Foon Tan wrote:
 +static inline int atomic_futex_op_xchg_set(int oparg, u32 __user *uaddr,
> +					   int *oldval)
> +{
> +	unsigned long flags;
> +	int ret;
> +
> +	local_irq_save(flags);
> +
> +	ret = get_user(*oldval, uaddr);
> +	if (!ret)
> +		ret = put_user(oparg, uaddr);

This is wrong as it gets. get_user() might fault and sleep.

You need a proper implementation, which handles fault exceptions.

Thanks,

	tglx
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