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From: Allen <>
To: Greg KH <>
	Linux Kernel Mailing List <>,
	Allen Pais <>,
	Allen Pais <>
Subject: Re: [RFC] PCI: allow sysfs file owner to read the config space with CAP_SYS_RAWIO
Date: Mon, 19 Oct 2020 18:30:16 +0530	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

> >
> >  Access to pci config space is explictly checked with CAP_SYS_ADMIN
> > in order to read configuration space past the frist 64B.
> >
> >  Since the path is only for reading, could we use CAP_SYS_RAWIO?
> Why?  What needs this reduced capability?

Thanks for the review.

We need read access to /sys/bus/pci/devices/,  We need write access to config,
remove, rescan & enable files under the device directory for each PCIe
functions & the downstream PCIe port.

We need r/w access to sysfs to unbind and rebind the root complex.

> > This patch contains a simpler fix, I would love to hear from the
> > Maintainers on the approach.
> >
> >  The other approach that I considered was to introduce and API
> > which would check for multiple capabilities, something similar to
> > perfmon_capable()/bpf_capable(). But I could not find more users
> > for the API and hence dropped it.
> >
> >  The problem I am trying to solve is to avoid handing out
> > CAP_SYS_ADMIN for extended reads of the PCI config space.
> Who is reading this config space that doesn't have admin rights?  And
> what are they doing with it?
> One big problem is that some devices will crash if you do this wrong,
> which is why we restricted it to root.  Hopefully all of those devices
> are now gone, but I don't think you can count on it.
> The "guaranteed safe" fields in the config space are already exported by
> sysfs for all users to read, are they not sufficient?
> thanks,
> greg k-h

       - Allen

  reply	other threads:[~2020-10-19 13:00 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-16  5:52 Allen Pais
2020-10-16  6:20 ` Greg KH
2020-10-19 13:00   ` Allen [this message]
2020-10-19 13:16     ` Greg KH
2020-10-19 13:21       ` Allen
2020-10-19 13:47         ` Greg KH
2020-10-19 14:32           ` Allen

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