linux-kernel - Re: [PATCH] RDMA/siw: fix pointer cast warning

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Date:   Fri, 16 Dec 2022 08:47:23 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     David Laight <David.Laight@...lab.com>
Cc:     Arnd Bergmann <arnd@...nel.org>,
        Bernard Metzler <bmt@...ich.ibm.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Leon Romanovsky <leon@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] RDMA/siw: fix pointer cast warning

On Thu, Dec 15, 2022 at 11:20 PM David Laight <David.Laight@...lab.com> wrote:

> From: Arnd Bergmann
> > Sent: 15 December 2022 17:04
> >
> > From: Arnd Bergmann <arnd@...db.de>
> >
> > The previous build fix left a remaining issue in configurations
> > with 64-bit dma_addr_t on 32-bit architectures:
> >
> > drivers/infiniband/sw/siw/siw_qp_tx.c: In function 'siw_get_pblpage':
> > drivers/infiniband/sw/siw/siw_qp_tx.c:32:37: error: cast to pointer from integer of different size [-
> > Werror=int-to-pointer-cast]
> >    32 |                 return virt_to_page((void *)paddr);
> >       |                                     ^
> >
> > Use the same double cast here that the driver uses elsewhere
> > to convert between dma_addr_t and void*.
> >
> > It took me a while to figure out why this driver does it
> > like this, as there is no hardware access and it just stores
> > kernel pointers in place of device addresses when communicating
> > with the rdma core and with user space.
>
> I hope that doesn't mean it is relying on user space only
> giving it back valid values?

It looks to me like this driver totally trusts userspace.

Yours,
Linus Walleij