linux-kernel - Re: [PATCH v4] usb: gadget: f_fs: try to fix AIO issue under ARM 64 bit TAGGED mode

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Message-ID: <20200228164848.GH4019108@arrakis.emea.arm.com>
Date:   Fri, 28 Feb 2020 16:48:48 +0000
From:   Catalin Marinas <catalin.marinas@....com>
To:     Macpaul Lin <macpaul.lin@...iatek.com>
Cc:     Matthias Brugger <matthias.bgg@...il.com>,
        Shen Jing <jingx.shen@...el.com>,
        Sasha Levin <sashal@...nel.org>,
        John Stultz <john.stultz@...aro.org>,
        Andrzej Pietrasiewicz <andrzej.p@...labora.com>,
        Vincent Pelletier <plr.vincent@...il.com>,
        Jerry Zhang <zhangjerry@...gle.com>, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org,
        Mediatek WSD Upstream <wsd_upstream@...iatek.com>,
        CC Hwang <cc.hwang@...iatek.com>,
        Loda Chou <loda.chou@...iatek.com>,
        Al Viro <viro@...iv.linux.org.uk>, stable@...r.kernel.org,
        andreyknvl@...gle.com, Peter Chen <peter.chen@....com>,
        Miles Chen <miles.chen@...iatek.com>, eugenis@...gle.com
Subject: Re: [PATCH v4] usb: gadget: f_fs: try to fix AIO issue under ARM 64
 bit TAGGED mode

On Wed, Feb 26, 2020 at 08:01:52PM +0800, Macpaul Lin wrote:
> diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
> index ce1d023..192935f 100644
> --- a/drivers/usb/gadget/function/f_fs.c
> +++ b/drivers/usb/gadget/function/f_fs.c
> @@ -715,7 +715,20 @@ static void ffs_epfile_io_complete(struct usb_ep *_ep, struct usb_request *req)
>  
>  static ssize_t ffs_copy_to_iter(void *data, int data_len, struct iov_iter *iter)
>  {
> -	ssize_t ret = copy_to_iter(data, data_len, iter);
> +	ssize_t ret;
> +
> +#if defined(CONFIG_ARM64)
> +	/*
> +	 * Replace tagged address passed by user space application before
> +	 * copying.
> +	 */
> +	if (IS_ENABLED(CONFIG_ARM64_TAGGED_ADDR_ABI) &&
> +		(iter->type == ITER_IOVEC)) {
> +		*(unsigned long *)&iter->iov->iov_base =
> +			(unsigned long)untagged_addr(iter->iov->iov_base);
> +	}
> +#endif
> +	ret = copy_to_iter(data, data_len, iter);
>  	if (likely(ret == data_len))
>  		return ret;

I had forgotten that we discussed a similar case already a few months
ago (thanks to Evgenii for pointing out). Do you have this commit
applied to your tree: df325e05a682 ("arm64: Validate tagged addresses in
access_ok() called from kernel threads")?

-- 
Catalin