[PATCH] efi/esrt: Allow ESRT access without CAP_SYS_ADMIN

[PATCH] efi/esrt: Allow ESRT access without CAP_SYS_ADMIN

[Nicholas Bishop]

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@google.com>
---
 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

Re: [PATCH] efi/esrt: Allow ESRT access without CAP_SYS_ADMIN

[Ard Biesheuvel]

On Fri, 12 May 2023 at 21:43, Nicholas Bishop <nicholasbishop@google.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@google.com>

Seems reasonable to me. Peter?

> ---
>  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
>

Re: [PATCH] efi/esrt: Allow ESRT access without CAP_SYS_ADMIN

[Ard Biesheuvel]

On Mon, 22 May 2023 at 10:11, Ard Biesheuvel <ardb@kernel.org> wrote:
>
> On Fri, 12 May 2023 at 21:43, Nicholas Bishop <nicholasbishop@google.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@google.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
> >

Re: [PATCH] efi/esrt: Allow ESRT access without CAP_SYS_ADMIN

[Peter Jones]

On Mon, May 22, 2023 at 4:11 AM Ard Biesheuvel <ardb@kernel.org> wrote:
>
> On Fri, 12 May 2023 at 21:43, Nicholas Bishop <nicholasbishop@google.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@google.com>
>
> Seems reasonable to me. Peter?

Yeah, I don't think we had any specific reason to limit it.

-- Peter