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

Overview

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().

Affected

• Linux >= b69a2afd5afce9bf6d56e349d6ab592c916e20f2 < 5bfa1941ec40d5bed68f3e3f22ea13aff9c6d67a
• Linux >= b69a2afd5afce9bf6d56e349d6ab592c916e20f2 < 43308106a1762b72f3b20a44b75b2df5cb25b77b
• Linux >= b69a2afd5afce9bf6d56e349d6ab592c916e20f2 < f11d7d088f5ed54b31c6735854c12845eb60eb4a
• Linux >= b69a2afd5afce9bf6d56e349d6ab592c916e20f2 < 9e1f51c1ad57cc76a0e8b5eb27038f8973fff4fa
• Linux >= b69a2afd5afce9bf6d56e349d6ab592c916e20f2 < 5366ec7d2f793ce703c403d7fd4c25a3db365b9d
• Linux >= b69a2afd5afce9bf6d56e349d6ab592c916e20f2 < 10d1c75ed4382a8e79874379caa2ead8952734f9
• Linux 6.0

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.