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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250929035620-mutt-send-email-mst@kernel.org>
Date: Mon, 29 Sep 2025 03:56:27 -0400
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Eugenio Perez Martin <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 Mon, Sep 29, 2025 at 07:41:13AM +0200, Eugenio Perez Martin wrote:
> On Fri, Sep 26, 2025 at 4:37 PM Michael S. Tsirkin <mst@...hat.com> wrote:
> >
> > 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?
> >
> 
> copy_from_user returns the number of bytes that could not be copied.
> For example when the object size in the kernel is less than n bytes
> long, check_copy_size returns false and copy_from_user returns n, the
> amount of size requested to copy.

oh, right. thanks!