linux-kernel - Re: [PATCH] efi/esrt: Allow ESRT access without CAP_SYS

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Date:   Fri, 2 Jun 2023 14:59:22 +0200
From:   Ard Biesheuvel <ardb@...nel.org>
To:     Nicholas Bishop <nicholasbishop@...gle.com>,
        Peter Jones <pjones@...hat.com>
Cc:     linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] efi/esrt: Allow ESRT access without CAP_SYS_ADMIN

On Mon, 22 May 2023 at 10:11, Ard Biesheuvel <ardb@...nel.org> wrote:
>
> On Fri, 12 May 2023 at 21:43, Nicholas Bishop <nicholasbishop@...gle.com> wrote:
> >
> > Access to the files in /sys/firmware/efi/esrt has been restricted to
> > CAP_SYS_ADMIN since support for ESRT was added, but this seems overly
> > restrictive given that the files are read-only and just provide
> > information about UEFI firmware updates.
> >
> > Remove the CAP_SYS_ADMIN restriction so that a non-root process can read
> > the files, provided a suitably-privileged process changes the file
> > ownership first. The files are still read-only and still owned by root by
> > default.
> >
> > Signed-off-by: Nicholas Bishop <nicholasbishop@...gle.com>
>
> Seems reasonable to me. Peter?
>

I've queued this up now.


> > ---
> >  drivers/firmware/efi/esrt.c | 4 ----
> >  1 file changed, 4 deletions(-)
> >
> > diff --git a/drivers/firmware/efi/esrt.c b/drivers/firmware/efi/esrt.c
> > index d5915272141f..aab96ab64a1a 100644
> > --- a/drivers/firmware/efi/esrt.c
> > +++ b/drivers/firmware/efi/esrt.c
> > @@ -95,10 +95,6 @@ static ssize_t esre_attr_show(struct kobject *kobj,
> >         struct esre_entry *entry = to_entry(kobj);
> >         struct esre_attribute *attr = to_attr(_attr);
> >
> > -       /* Don't tell normal users what firmware versions we've got... */
> > -       if (!capable(CAP_SYS_ADMIN))
> > -               return -EACCES;
> > -
> >         return attr->show(entry, buf);
> >  }
> >
> > --
> > 2.40.1.606.ga4b1b128d6-goog
> >