linux-kernel - Re: [PATCH] efivarfs: fix NULL-deref on mount when no efivars

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Date:   Thu, 26 Jan 2023 21:32:27 +0100
From:   Ard Biesheuvel <ardb@...nel.org>
To:     Johan Hovold <johan+linaro@...nel.org>
Cc:     Jeremy Kerr <jk@...abs.org>,
        Maximilian Luz <luzmaximilian@...il.com>,
        linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org,
        Steev Klimaszewski <steev@...i.org>
Subject: Re: [PATCH] efivarfs: fix NULL-deref on mount when no efivars

On Thu, 26 Jan 2023 at 12:23, Johan Hovold <johan+linaro@...nel.org> wrote:
>
> The VFS calls kill_sb() also in case mount fails in get_tree().
>
> Add the missing check to make sure that efivars has been registered also
> to kill_sb() to avoid dereferencing a NULL pointer when trying to remove
> efivar entries.
>
> Fixes: c3fd71b428b8 ("efivarfs: always register filesystem")
> Reported-by: Steev Klimaszewski <steev@...i.org>
> Signed-off-by: Johan Hovold <johan+linaro@...nel.org>

Thanks - I have squashed this with the original patch.

> ---
>  fs/efivarfs/super.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/fs/efivarfs/super.c b/fs/efivarfs/super.c
> index b67d431c861a..482d612b716b 100644
> --- a/fs/efivarfs/super.c
> +++ b/fs/efivarfs/super.c
> @@ -246,6 +246,9 @@ static void efivarfs_kill_sb(struct super_block *sb)
>  {
>         kill_litter_super(sb);
>
> +       if (!efivar_is_available())
> +               return;
> +
>         /* Remove all entries and destroy */
>         efivar_entry_iter(efivarfs_destroy, &efivarfs_list, NULL);
>  }
> --
> 2.39.1
>