Messages in this thread | | | Subject | Re: [PATCH 0/4] Fix misused kernel_read_file() enums | From | Hans de Goede <> | Date | Wed, 8 Jul 2020 13:58:47 +0200 |
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Hi,
On 7/8/20 1:55 PM, Luis Chamberlain wrote: > On Wed, Jul 08, 2020 at 01:37:41PM +0200, Hans de Goede wrote: >> 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@redhat.com> >> >> 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. > > BTW is there any testing covered by the selftests for the firmware > laoder which would have caputured this? If not can you extend > it with something to capture this case you ran into?
This was not a firmware-loading issue. For me in my tests, which were limited to 1 device, patch 4/4, which only touches the module-loading code, stopped module loading from working.
Since my test device has / on an eMMC and the kernel config I'm using has mmc-block as a module, things just hung in the initrd since no modules could be loaded, so I did not debug this any further. Dropping patch 4/4 from my local tree solved this.
Regards,
Hans
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