Re: [PATCH 0/4] Fix misused kernel_read_file() enums

Hans de Goede
2020-07-08T11:02:09Z

Hi,

On 7/7/20 10:19 AM, Kees Cook wrote:
> Hi,
>
> In looking for closely at the additions that got made to the
> kernel_read_file() enums, I noticed that FIRMWARE_PREALLOC_BUFFER
> and FIRMWARE_EFI_EMBEDDED were added, but they are not appropriate
> *kinds* of files for the LSM to reason about. They are a "how" and
> "where", respectively. Remove these improper aliases and refactor the
> code to adapt to the changes.
>
> Additionally adds in missing calls to security_kernel_post_read_file()
> in the platform firmware fallback path (to match the sysfs firmware
> fallback path) and in module loading. I considered entirely removing
> security_kernel_post_read_file() hook since it is technically unused,
> but IMA probably wants to be able to measure EFI-stored firmware images,
> so I wired it up and matched it for modules, in case anyone wants to
> move the module signature checks out of the module core and into an LSM
> to avoid the current layering violations.
>
> This touches several trees, and I suspect it would be best to go through
> James's LSM tree.
>
> Thanks!

I've done some quick tests on this series to make sure that
the efi embedded-firmware support did not regress.
That still works fine, so this series is;

Tested-by: Hans de Goede <hdegoede@redhat.com>

Regards,

Hans

>
> -Kees
>
> Kees Cook (4):
> firmware_loader: EFI firmware loader must handle pre-allocated buffer
> fs: Remove FIRMWARE_PREALLOC_BUFFER from kernel_read_file() enums
> fs: Remove FIRMWARE_EFI_EMBEDDED from kernel_read_file() enums
> module: Add hook for security_kernel_post_read_file()
>
> drivers/base/firmware_loader/fallback_platform.c | 12 ++++++++++--
> drivers/base/firmware_loader/main.c | 5 ++---
> fs/exec.c | 7 ++++---
> include/linux/fs.h | 3 +--
> include/linux/lsm_hooks.h | 6 +++++-
> kernel/module.c | 7 ++++++-
> security/integrity/ima/ima_main.c | 6 ++----
> 7 files changed, 30 insertions(+), 16 deletions(-)
>