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

[Hans de Goede]

Hi,

On 7/8/20 1:01 PM, Hans de Goede wrote:
> 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@xxxxxxxxxx>

I made a mistake during testing I was not actually running the
kernel with the patches added.

After fixing that I did find a problem, patch 4/4:
"module: Add hook for security_kernel_post_read_file()"

Breaks module-loading for me. This is with the 4 patches
on top of 5.8.0-rc4, so this might just be because I'm
not using the right base.

With patch 4/4 reverted things work fine for me.

So, please only add my Tested-by to patches 1-3.

Regards,

Hans



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