[PATCH v5 5/8] ima: kexec: move IMA log copy from kexec load to execute

[Tushar Sugandhi]

ima_dump_measurement_list() is called during kexec 'load', which may
result in loss of IMA measurements during kexec soft reboot.  It needs
to be called during kexec 'execute'.

This patch includes the following changes:
 - Call kimage_file_post_load() from kexec_file_load() syscall only for
   kexec soft reboot scenarios and not for KEXEC_FILE_ON_CRASH.  It will
   map the IMA segment, and register reboot notifier for the function
   ima_update_kexec_buffer() which would copy the IMA log at kexec soft
   reboot.
 - Make kexec_segment_size variable local static to the file, for it to be
   accessible both during kexec 'load' and 'execute'.
 - Move ima_dump_measurement_list() call from ima_add_kexec_buffer()
   to ima_update_kexec_buffer().
 - Remove ima_reset_kexec_file() call from ima_add_kexec_buffer(), now
   that the buffer is being copied at kexec 'execute', and resetting the
   file at kexec 'load' will corrupt the buffer.

Signed-off-by: Tushar Sugandhi <tusharsu at linux.microsoft.com>
---
 kernel/kexec_file.c                |  3 ++
 security/integrity/ima/ima_kexec.c | 45 +++++++++++++++++++-----------
 2 files changed, 32 insertions(+), 16 deletions(-)

diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index fe59cb7c179d..2d5df320c34f 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -410,6 +410,9 @@ SYSCALL_DEFINE5(kexec_file_load, int, kernel_fd, int, initrd_fd,
 
 	kimage_terminate(image);
 
+	if (!(flags & KEXEC_FILE_ON_CRASH))
+		kimage_file_post_load(image);
+
 	ret = machine_kexec_post_load(image);
 	if (ret)
 		goto out;
diff --git a/security/integrity/ima/ima_kexec.c b/security/integrity/ima/ima_kexec.c
index 1d4d6c122d82..98fc9b9782a2 100644
--- a/security/integrity/ima/ima_kexec.c
+++ b/security/integrity/ima/ima_kexec.c
@@ -19,6 +19,7 @@
 #ifdef CONFIG_IMA_KEXEC
 static struct seq_file ima_kexec_file;
 static void *ima_kexec_buffer;
+static size_t kexec_segment_size;
 static bool ima_kexec_update_registered;
 
 static void ima_reset_kexec_file(struct seq_file *sf)
@@ -129,7 +130,6 @@ 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;
 
 	/*
@@ -154,14 +154,6 @@ 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;
@@ -179,12 +171,6 @@ void ima_add_kexec_buffer(struct kimage *image)
 	image->ima_segment_index = image->nr_segments - 1;
 	image->is_ima_segment_index_set = true;
 
-	/*
-	 * kexec owns kexec_buffer after kexec_add_buffer() is called
-	 * and it will vfree() that buffer.
-	 */
-	ima_reset_kexec_file(&ima_kexec_file);
-
 	kexec_dprintk("kexec measurement buffer for the loaded kernel at 0x%lx.\n",
 		      kbuf.mem);
 }
@@ -195,7 +181,34 @@ void ima_add_kexec_buffer(struct kimage *image)
 static int ima_update_kexec_buffer(struct notifier_block *self,
 				   unsigned long action, void *data)
 {
-	return NOTIFY_OK;
+	void *buf = NULL;
+	size_t buf_size;
+	int ret = NOTIFY_OK;
+
+	if (!kexec_in_progress) {
+		pr_info("%s: No kexec in progress.\n", __func__);
+		return ret;
+	}
+
+	if (!ima_kexec_buffer) {
+		pr_err("%s: Kexec buffer not set.\n", __func__);
+		return ret;
+	}
+
+	ret = ima_dump_measurement_list(&buf_size, &buf,
+					kexec_segment_size);
+
+	if (!buf) {
+		pr_err("%s: Dump measurements failed. Error:%d\n",
+		       __func__, ret);
+		goto out;
+	}
+	memcpy(ima_kexec_buffer, buf, buf_size);
+out:
+	kimage_unmap_segment(ima_kexec_buffer);
+	ima_kexec_buffer = NULL;
+
+	return ret;
 }
 
 struct notifier_block update_buffer_nb = {
-- 
2.25.1