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SubjectRe: [PATCH 1/2] fs/efivarfs: restrict inode permissions
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On 02/15/2018 10:22 AM, Joe Konno wrote:
> From: Joe Konno <joe.konno@intel.com>
>
> Efivarfs nodes are created with group and world readable permissions.
> Reading certain EFI variables trigger SMIs. So, this is a potential DoS
> surface.
>
> Make permissions more restrictive-- only the owner may read or write to
> created inodes.
>
> Suggested-by: Andi Kleen <ak@linux.intel.com>
> Reported-by: Tony Luck <tony.luck@intel.com>
> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Cc: Matthew Garrett <matthew.garrett@nebula.com>
> Cc: Jeremy Kerr <jk@ozlabs.org>
> Cc: linux-efi@vger.kernel.org
> Cc: stable@vger.kernel.org
> Signed-off-by: Joe Konno <joe.konno@intel.com>

The discussion in this thread has gone on too long, so:

Acked-by: Andy Lutomirski <luto@kernel.org>

And yes, this patch will break a couple of minor usecases, but IMO those
usecases deserve to break.

> ---
> fs/efivarfs/super.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/fs/efivarfs/super.c b/fs/efivarfs/super.c
> index 5b68e4294faa..ca98c4e31eb7 100644
> --- a/fs/efivarfs/super.c
> +++ b/fs/efivarfs/super.c
> @@ -145,7 +145,7 @@ static int efivarfs_callback(efi_char16_t *name16, efi_guid_t vendor,
>
> name[len + EFI_VARIABLE_GUID_LEN+1] = '\0';
>
> - inode = efivarfs_get_inode(sb, d_inode(root), S_IFREG | 0644, 0,
> + inode = efivarfs_get_inode(sb, d_inode(root), S_IFREG | 0600, 0,
> is_removable);
> if (!inode)
> goto fail_name;
> @@ -207,7 +207,7 @@ static int efivarfs_fill_super(struct super_block *sb, void *data, int silent)
> sb->s_d_op = &efivarfs_d_ops;
> sb->s_time_gran = 1;
>
> - inode = efivarfs_get_inode(sb, NULL, S_IFDIR | 0755, 0, true);
> + inode = efivarfs_get_inode(sb, NULL, S_IFDIR | 0700, 0, true);
> if (!inode)
> return -ENOMEM;
> inode->i_op = &efivarfs_dir_inode_operations;
>

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