RE: Re: [PATCH] RDMA/siw: fix pointer cast warning

[Bernard Metzler]

> -----Original Message-----
> From: Linus Walleij <linus.walleij@xxxxxxxxxx>
> Sent: Friday, 16 December 2022 08:47
> To: David Laight <David.Laight@xxxxxxxxxx>
> Cc: Arnd Bergmann <arnd@xxxxxxxxxx>; Bernard Metzler <BMT@xxxxxxxxxxxxxx>;
> Jason Gunthorpe <jgg@xxxxxxxx>; Leon Romanovsky <leon@xxxxxxxxxx>; Arnd
> Bergmann <arnd@xxxxxxxx>; linux-rdma@xxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx
> Subject: [EXTERNAL] Re: [PATCH] RDMA/siw: fix pointer cast warning
> 
> On Thu, Dec 15, 2022 at 11:20 PM David Laight <David.Laight@xxxxxxxxxx>
> wrote:
> 
> > From: Arnd Bergmann
> > > Sent: 15 December 2022 17:04
> > >
> > > From: Arnd Bergmann <arnd@xxxxxxxx>
> > >
> > > 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.
> 

Shame on me. Yes, somehow, an access_ok((void __user *)start, len)
is missing! Let me fix that when I am back at my desk. Seems it needs
immediate action.

Many thanks for pointing that out!
Bernard.

> Yours,
> Linus Walleij