On 10/5/23 14:25, Tushar Sugandhi wrote:
In the current IMA implementation, ima_dump_measurement_list() is called
during the kexec 'load' operation. This can result in loss of IMA
measurements taken between the 'load' and 'execute' phases when the
system goes through Kexec soft reboot to a new Kernel. The call to the
function ima_dump_measurement_list() needs to be moved out of the
function ima_add_kexec_buffer() and needs to be called during the kexec
'execute' operation.
Implement a function ima_update_kexec_buffer() that is called during
kexec 'execute', allowing IMA to update the measurement list with the
events between kexec 'load' and 'execute'. Move the
ima_dump_measurement_list() call from ima_add_kexec_buffer() to
ima_update_kexec_buffer(). Make ima_kexec_buffer and kexec_segment_size
variables global, so that they can be accessed during both kexec 'load'
and 'execute'. Add functions ima_measurements_suspend() and
ima_measurements_resume() to set and reset the 'suspend_ima_measurements'
variable respectively, to suspend/resume IMA measurements. Use
the existing 'ima_extend_list_mutex' to ensure that the operations are
thread-safe. These function calls will help maintaining the integrity
of the IMA log while it is being copied to the new Kernel's buffer.
Add a reboot notifier_block 'update_buffer_nb' to ensure
the function ima_update_kexec_buffer() gets called during kexec
soft-reboot.
Signed-off-by: Tushar Sugandhi<tusha...@linux.microsoft.com>
---
security/integrity/ima/ima.h | 2 ++
security/integrity/ima/ima_kexec.c | 58 +++++++++++++++++++++++++-----
security/integrity/ima/ima_queue.c | 18 ++++++++++
3 files changed, 69 insertions(+), 9 deletions(-)
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index c29db699c996..49a6047dd8eb 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -161,6 +161,8 @@ bool ima_template_has_modsig(const struct ima_template_desc
*ima_template);
int ima_restore_measurement_entry(struct ima_template_entry *entry);
int ima_restore_measurement_list(loff_t bufsize, void *buf);
int ima_measurements_show(struct seq_file *m, void *v);
+void ima_measurements_suspend(void);
+void ima_measurements_resume(void);
unsigned long ima_get_binary_runtime_size(void);
int ima_init_template(void);
void ima_init_template_list(void);
diff --git a/security/integrity/ima/ima_kexec.c
b/security/integrity/ima/ima_kexec.c
index 307e07991865..2c11bbe6efef 100644
--- a/security/integrity/ima/ima_kexec.c
+++ b/security/integrity/ima/ima_kexec.c
@@ -17,6 +17,8 @@
#ifdef CONFIG_IMA_KEXEC
struct seq_file ima_kexec_file;
struct ima_kexec_hdr ima_khdr;
+static void *ima_kexec_buffer;
+static size_t kexec_segment_size;
void ima_clear_kexec_file(void)
{
@@ -142,7 +144,6 @@ void ima_add_kexec_buffer(struct kimage *image)
/* use more understandable variable names than defined in kbuf */
void *kexec_buffer = NULL;
size_t kexec_buffer_size;
- size_t kexec_segment_size;
int ret;
/*
@@ -167,14 +168,6 @@ void ima_add_kexec_buffer(struct kimage *image)
return;
}
- ret = ima_dump_measurement_list(&kexec_buffer_size, &kexec_buffer,
- kexec_segment_size);
- if (ret < 0) {
- pr_err("%s: Failed to dump IMA measurements. Error:%d.\n",
- __func__, ret);
- return;
- }
-
kbuf.buffer = kexec_buffer;
kbuf.bufsz = kexec_buffer_size;
kbuf.memsz = kexec_segment_size;
@@ -192,6 +185,53 @@ void ima_add_kexec_buffer(struct kimage *image)
pr_debug("kexec measurement buffer for the loaded kernel at 0x%lx.\n",
kbuf.mem);
}
+
+/*
+ * Called during kexec execute so that IMA can update the measurement list.
+ */
+static int ima_update_kexec_buffer(struct notifier_block *self,
+ unsigned long action, void *data)
+{
+ void *buf = NULL;
+ size_t buf_size;
+ bool resume = false;
+ int ret;
+
+ if (!kexec_in_progress) {
+ pr_info("%s: No kexec in progress.\n", __func__);
+ return NOTIFY_OK;
+ }
+
+ if (!ima_kexec_buffer) {
+ pr_err("%s: Kexec buffer not set.\n", __func__);
+ return NOTIFY_OK;
+ }
+
+ ima_measurements_suspend();
+
+ buf_size = ima_get_binary_runtime_size();
There doesn't seem to be a need to call this function and pass in the
binary runtime size into the dump function. You should be able to remove it.
+ ret = ima_dump_measurement_list(&buf_size, &buf,
+ kexec_segment_size);
+
+ if (!buf || ret < 0) {
I don't think this function can (or should) ever return ret >= 0 with
buf == NULL.
+ pr_err("%s: Dump measurements failed. Error:%d\n",
+ __func__, ret);
+ resume = true;
+ goto out;
+ }
+ memcpy(ima_kexec_buffer, buf, buf_size);
+out:
+ ima_kexec_buffer = NULL;
+
+ if (resume)
+ ima_measurements_resume();
+
+ return NOTIFY_OK;
+}
+struct notifier_block update_buffer_nb = {
+ .notifier_call = ima_update_kexec_buffer,
+};
+
#endif /* IMA_KEXEC */
/*
diff --git a/security/integrity/ima/ima_queue.c
b/security/integrity/ima/ima_queue.c
index 532da87ce519..9e7d1196006e 100644
--- a/security/integrity/ima/ima_queue.c
+++ b/security/integrity/ima/ima_queue.c
@@ -44,6 +44,11 @@ struct ima_h_table ima_htable = {
*/
static DEFINE_MUTEX(ima_extend_list_mutex);
+/*
+ * Used internally by the kernel to suspend-resume ima measurements.
+ */
+static atomic_t suspend_ima_measurements;
+
/* lookup up the digest value in the hash table, and return the entry */
static struct ima_queue_entry *ima_lookup_digest_entry(u8 *digest_value,
int pcr)
@@ -147,6 +152,19 @@ static int ima_pcr_extend(struct tpm_digest *digests_arg,
int pcr)
pr_err("Error Communicating to TPM chip, result: %d\n", result);
return result;
}
+void ima_measurements_suspend(void)
+{
+ mutex_lock(&ima_extend_list_mutex);
+ atomic_set(&suspend_ima_measurements, 1);
+ mutex_unlock(&ima_extend_list_mutex);
+}
+
+void ima_measurements_resume(void)
+{
+ mutex_lock(&ima_extend_list_mutex);
+ atomic_set(&suspend_ima_measurements, 0);
+ mutex_unlock(&ima_extend_list_mutex);
+}
/*
* Add template entry to the measurement list and hash table, and
