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

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Message-ID: <CAMj1kXERDgT1cM-2P4M=DBGU0Wzbc-zewGsJjLQoQHpC3ds-4g@mail.gmail.com>
Date:   Mon, 22 May 2023 10:11:36 +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 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?

> ---
>  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
>