linux-kernel - Re: [PATCH v5 0/6] Add multiple address spaces support to VDUSE

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Message-ID: <20250926103421-mutt-send-email-mst@kernel.org>
Date: Fri, 26 Sep 2025 10:37:20 -0400
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Eugenio Pérez <eperezma@...hat.com>
Cc: Yongji Xie <xieyongji@...edance.com>, linux-kernel@...r.kernel.org,
	Maxime Coquelin <mcoqueli@...hat.com>,
	Stefano Garzarella <sgarzare@...hat.com>,
	Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, Cindy Lu <lulu@...hat.com>,
	virtualization@...ts.linux.dev, Laurent Vivier <lvivier@...hat.com>,
	jasowang@...hat.com
Subject: Re: [PATCH v5 0/6] Add multiple address spaces support to VDUSE

On Fri, Sep 26, 2025 at 12:14:26PM +0200, Eugenio Pérez wrote:
> PATCH v5:
> * Properly return errno if copy_to_user returns >0 in VDUSE_IOTLB_GET_FD
>   ioctl (Jason).

???

I think copy_to_user returns an unsigned value: the number of bytes copied.


static __always_inline unsigned long __must_check
copy_from_user(void *to, const void __user *from, unsigned long n)
{
        if (!check_copy_size(to, n, false))
                return n;
#ifdef INLINE_COPY_FROM_USER
        return _inline_copy_from_user(to, from, n);
#else
        return _copy_from_user(to, from, n);
#endif
}


so, how does the patch work then?

-- 
MST