In the Linux kernel, the following vulnerability has been resolved: ima: verify the previous...

In the Linux kernel, the following vulnerability has been resolved:

ima: verify the previous kernel's IMA buffer lies in addressable RAM

Patch series "Address page fault in ima_restore_measurement_list()", v3.

When the second-stage kernel is booted via kexec with a limiting command
line such as "mem=<size>" we observe a pafe fault that happens.

BUG: unable to handle page fault for address: ffff97793ff47000
RIP: ima_restore_measurement_list+0xdc/0x45a
#PF: error_code(0x0000)  not-present page

This happens on x86_64 only, as this is already fixed in aarch64 in
commit: cbf9c4b9617b ("of: check previous kernel's ima-kexec-buffer
against memory bounds")

This patch (of 3):

When the second-stage kernel is booted with a limiting command line (e.g.
"mem=<size>"), the IMA measurement buffer handed over from the previous
kernel may fall outside the addressable RAM of the new kernel. Accessing
such a buffer can fault during early restore.

Introduce a small generic helper, ima_validate_range(), which verifies
that a physical [start, end] range for the previous-kernel IMA buffer lies
within addressable memory:
- On x86, use pfn_range_is_mapped().
- On OF based architectures, use page_is_ram().