On 1/28/2025 9:29 AM, Stefan Berger wrote:

On 1/28/25 10:28 AM, Stefan Berger wrote:

quoted

On 1/24/25 5:55 PM, steven chen wrote:

quoted

The amount of memory allocated at kexec load, even with the extra 
memory
allocated, might not be large enough for the entire measurement 
list.  The
indeterminate interval between kexec 'load' and 'execute' could 
exacerbate
this problem.

Define two new IMA events, 'kexec_load' and 'kexec_execute', to be
measured as critical data at kexec 'load' and 'execute' respectively.
Report the allocated kexec segment size, IMA binary log size and the
runtime measurements count as part of those events.

These events, and the values reported through them, serve as markers in
the IMA log to verify the IMA events are captured during kexec soft
reboot.  The presence of a 'kexec_load' event in between the last two
'boot_aggregate' events in the IMA log implies this is a kexec soft
reboot, and not a cold-boot. And the absence of 'kexec_execute' event
after kexec soft reboot implies missing events in that window which
results in inconsistency with TPM PCR quotes, necessitating a cold boot
for a successful remote attestation.

Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
Author: Tushar Sugandhi [off-list ref]
Signed-off-by: Tushar Sugandhi <redacted>
Signed-off-by: steven chen <redacted>
---
  security/integrity/ima/ima_kexec.c | 23 +++++++++++++++++++++++
  1 file changed, 23 insertions(+)

diff --git a/security/integrity/ima/ima_kexec.c 

b/security/integrity/ ima/ima_kexec.c
index c9c916f69ca7..d416ca0382cb 100644

--- a/security/integrity/ima/ima_kexec.c
+++ b/security/integrity/ima/ima_kexec.c

@@ -17,6 +17,8 @@

  #include "ima.h"
  #ifdef CONFIG_IMA_KEXEC
+#define IMA_KEXEC_EVENT_LEN 256
+
  static struct seq_file ima_kexec_file;
  static void *ima_kexec_buffer;
  static size_t kexec_segment_size;

@@ -36,6 +38,24 @@ static void ima_free_kexec_file_buf(struct 

seq_file *sf)
      ima_reset_kexec_file(sf);
  }
+static void ima_measure_kexec_event(const char *event_name)
+{
+    char ima_kexec_event[IMA_KEXEC_EVENT_LEN];
+    size_t buf_size = 0;
+    long len;
+
+    buf_size = ima_get_binary_runtime_size();
+    len = atomic_long_read(&ima_htable.len);
+
+    scnprintf(ima_kexec_event, IMA_KEXEC_EVENT_LEN,
+ "kexec_segment_size=%lu;ima_binary_runtime_size=%lu;"
+            "ima_runtime_measurements_count=%ld;",
+                kexec_segment_size, buf_size, len);
+
+    ima_measure_critical_data("ima_kexec", event_name, 
ima_kexec_event,
+                    strlen(ima_kexec_event), false, NULL, 0);
+}
+
  static int ima_alloc_kexec_file_buf(size_t segment_size)
  {
      /*

@@ -60,6 +80,7 @@ static int ima_alloc_kexec_file_buf(size_t 

segment_size)
  out:
      ima_kexec_file.read_pos = 0;
      ima_kexec_file.count = sizeof(struct ima_kexec_hdr); /* 
reserved space */
+    ima_measure_kexec_event("kexec_load");
      return 0;
  }

@@ -206,6 +227,8 @@ static int ima_update_kexec_buffer(struct 

notifier_block *self,
      if (ret)
          pr_err("Dump measurements failed. Error:%d\n", ret);
+    else
+        ima_measure_kexec_event("kexec_execute");

The problem is that this here ^^^^ currently comes after this block:

        ret = ima_dump_measurement_list(&buf_size, &buf,
                                        kexec_segment_size);

        if (ret)
                pr_err("Dump measurements failed. Error:%d\n", ret);
        else
                ima_measure_kexec_event("kexec_execute");  <--- after 
the dump

It has to be done before so that whatever it adds to the measurement 
list gets dumped as well. So this works for my testing:

+       ima_measure_kexec_event("kexec_execute");
+
        ret = ima_dump_measurement_list(&buf_size, &buf,
                                        kexec_segment_size);

        if (ret)
                pr_err("Dump measurements failed. Error:%d\n", ret);

quoted

quoted

      if (buf_size != 0)
          memcpy(ima_kexec_buffer, buf, buf_size);

I have been doing kexec's (on ppc64 KVM) applying one patch after 
another in this series and then testing with this command:

evmctl ima_measurement --ignore-violations /sys/kernel/security/ima/ 
binary_runtime_measurements

Unfortunately it breaks at this patch. I am not sure what it is due to.

Thanks Stefan. Will update it in next release