Re: [PATCH for-rc] RDMA/qedr: Fix doorbell bar mapping for dpi > 1

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From: Jason Gunthorpe <jgg@xxxxxxxxxxxx>
Sent: Tuesday, May 15, 2018 5:22 PM

> On Tue, May 15, 2018 at 11:06:21AM +0000, Kalderon, Michal wrote:
> > > From: linux-rdma-owner@xxxxxxxxxxxxxxx [mailto:linux-rdma-
> > > owner@xxxxxxxxxxxxxxx] On Behalf Of Jason Gunthorpe
> > > On Mon, May 14, 2018 at 08:01:32PM +0000, Kalderon, Michal wrote:
> > > > From: linux-rdma-owner@xxxxxxxxxxxxxxx
> > > > <linux-rdma-owner@xxxxxxxxxxxxxxx> on behalf of Jason Gunthorpe
> > > > <jgg@xxxxxxxxxxxx>
> > > >
> > > > > > > >  1 file changed, 28 insertions(+), 31 deletions(-)
> > > > > > > >
> > > > > > > > Please don't leak kernel pointers [1], and use %pK instead of %x [2].
> > > > > > >
> > > > > > > [1] https://lwn.net/Articles/735589/ [2]
> > > > > > > Documentation/core-api/printk-formats.rst
> > > > > > >
> > > > > > > Thanks
> > > >
> > > > > > Thanks for pointing these out. I was not familiar with this
> > > > > > convention. However, the addresses Which are printed below are the
> > > > > > physical doorbell addresses which don't
> > > >
> > > > > I think PCI physical addresses are expected to be protected as well.
> > > >
> > > > Not sure what can be done though with this physical address, as it is
> > > > an address into the devices doorbell -> any attempt to write data that
> > > > is not in the doorbell format will be dropped by device.
> > >
> > > It obscures information about the kernel memory layout which is the point of
> > > all of this.
> > >
> > > If you want to report the doorbell address for debugging then report it as an
> > > offset from the start of the device's bar.
> >
> > The doorbell bar address (all bars ) is visible with a simple lspci -vv ( also when run
> > with non-priviledged user and kptr_restrict=2)  Why is reporting it in printk
> > a leak in this case?
> 
> I didn't make feature..
> 
> But if I recall, lspci -vv only shows the bar physical address because
> your system is not in a high enough security mode?
>
I'll check again, thanks. In any case, following discussion with Leon I saw that using pK
does give the same information needed, sent a v2 with the fix. 
thanks,
Michal

>
> Jason
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