[PATCH 6/6] kexec: measure TPM update counter in ima log at kexec load

[Tushar Sugandhi]

IMA measurements snapshot occurs at kexec 'load', but any additional
measurements between 'load' and kexec 'execute' aren't carried over
post kexec soft-reboot.[1] This may lead to TPM PCRs extending with
events that are not reflected in the new Kernel's IMA log.  By measuring
the TPM update counter at kexec 'load' and at ima_init after the kexec
soft-reboot, the remote attestation service can identify potentially
lost events by comparing the log event count with the counter difference.

Measure the TPM update counter at kexec image load.

[1] https://lore.kernel.org/all/20230703215709.1195644-1-tusharsu@linux.microsoft.com/
    ima: measure events between kexec load and execute

Signed-off-by: Tushar Sugandhi <tusharsu at linux.microsoft.com>
---
 kernel/kexec_file.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index f1a0e4e3fb5c..4b6391b02c5a 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -246,6 +246,9 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd,
 				  image->cmdline_buf_len - 1);
 	}
 
+	/* Measures TPM update counter at kexec load. */
+	ima_measure_update_counter("kexec_load_tpm_update_counter");
+
 	/* IMA needs to pass the measurement list to the next kernel. */
 	ima_add_kexec_buffer(image);
 
-- 
2.25.1