[PATCH v4 5/5] IMA: Demonstration code for kexec buffer passing.
Thiago Jung Bauermann
bauerman at linux.vnet.ibm.com
Tue Aug 30 10:45:05 PDT 2016
This shows how kernel code can use the kexec buffer passing mechanism
to pass information to the next kernel.
This patch is not intended to be committed.
[akpm at linux-foundation.org: coding-style fixes]
Signed-off-by: Thiago Jung Bauermann <bauerman at linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
---
include/linux/ima.h | 11 +++++
kernel/kexec_file.c | 4 ++
security/integrity/ima/ima.h | 5 +++
security/integrity/ima/ima_init.c | 26 +++++++++++
security/integrity/ima/ima_template.c | 85 +++++++++++++++++++++++++++++++++++
5 files changed, 131 insertions(+)
diff --git a/include/linux/ima.h b/include/linux/ima.h
index 0eb7c2e7f0d6..96528d007139 100644
--- a/include/linux/ima.h
+++ b/include/linux/ima.h
@@ -11,6 +11,7 @@
#define _LINUX_IMA_H
#include <linux/fs.h>
+#include <linux/kexec.h>
struct linux_binprm;
#ifdef CONFIG_IMA
@@ -23,6 +24,10 @@ extern int ima_post_read_file(struct file *file, void *buf, loff_t size,
enum kernel_read_file_id id);
extern void ima_post_path_mknod(struct dentry *dentry);
+#ifdef CONFIG_KEXEC_FILE
+extern void ima_add_kexec_buffer(struct kimage *image);
+#endif
+
#else
static inline int ima_bprm_check(struct linux_binprm *bprm)
{
@@ -60,6 +65,12 @@ static inline void ima_post_path_mknod(struct dentry *dentry)
return;
}
+#ifdef CONFIG_KEXEC_FILE
+static inline void ima_add_kexec_buffer(struct kimage *image)
+{
+}
+#endif
+
#endif /* CONFIG_IMA */
#ifdef CONFIG_IMA_APPRAISE
diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index 0e90d1446cb0..75c1b8d67a72 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -19,6 +19,7 @@
#include <linux/mutex.h>
#include <linux/list.h>
#include <linux/fs.h>
+#include <linux/ima.h>
#include <crypto/hash.h>
#include <crypto/sha.h>
#include <linux/syscalls.h>
@@ -248,6 +249,9 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd,
}
}
+ /* IMA needs to pass the measurement list to the next kernel. */
+ ima_add_kexec_buffer(image);
+
/* Call arch image load handlers */
ldata = arch_kexec_kernel_image_load(image);
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index db25f54a04fe..0334001055d7 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -102,6 +102,11 @@ struct ima_queue_entry {
};
extern struct list_head ima_measurements; /* list of all measurements */
+#ifdef CONFIG_KEXEC_FILE
+extern void *kexec_buffer;
+extern size_t kexec_buffer_size;
+#endif
+
/* Internal IMA function definitions */
int ima_init(void);
int ima_fs_init(void);
diff --git a/security/integrity/ima/ima_init.c b/security/integrity/ima/ima_init.c
index 32912bd54ead..a1924d0f3b2b 100644
--- a/security/integrity/ima/ima_init.c
+++ b/security/integrity/ima/ima_init.c
@@ -21,6 +21,7 @@
#include <linux/scatterlist.h>
#include <linux/slab.h>
#include <linux/err.h>
+#include <linux/kexec.h>
#include "ima.h"
@@ -104,6 +105,29 @@ void __init ima_load_x509(void)
}
#endif
+#ifdef CONFIG_KEXEC_FILE
+static void ima_load_kexec_buffer(void)
+{
+ int rc;
+
+ /* Fetch the buffer from the previous kernel, if any. */
+ rc = kexec_get_handover_buffer(&kexec_buffer, &kexec_buffer_size);
+ if (rc == 0) {
+ /* Demonstrate that buffer handover works. */
+ pr_err("kexec buffer contents: %s\n", (char *) kexec_buffer);
+ pr_err("kexec buffer contents after update: %s\n",
+ (char *) kexec_buffer + 4 * PAGE_SIZE + 10);
+
+ kexec_free_handover_buffer();
+ } else if (rc == -ENOENT)
+ pr_debug("No kexec buffer from the previous kernel.\n");
+ else
+ pr_debug("Error restoring kexec buffer: %d\n", rc);
+}
+#else
+static void ima_load_kexec_buffer(void) { }
+#endif
+
int __init ima_init(void)
{
u8 pcr_i[TPM_DIGEST_SIZE];
@@ -134,5 +158,7 @@ int __init ima_init(void)
ima_init_policy();
+ ima_load_kexec_buffer();
+
return ima_fs_init();
}
diff --git a/security/integrity/ima/ima_template.c b/security/integrity/ima/ima_template.c
index febd12ed9b55..e9ac260534b6 100644
--- a/security/integrity/ima/ima_template.c
+++ b/security/integrity/ima/ima_template.c
@@ -15,6 +15,8 @@
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+#include <linux/kexec.h>
+#include <linux/reboot.h>
#include "ima.h"
#include "ima_template_lib.h"
@@ -182,6 +184,89 @@ static int template_desc_init_fields(const char *template_fmt,
return 0;
}
+#ifdef CONFIG_KEXEC_FILE
+void *kexec_buffer;
+size_t kexec_buffer_size;
+
+/* Physical address of the measurement buffer in the next kernel. */
+unsigned long kexec_buffer_load_addr;
+
+/*
+ * Called during reboot. IMA can add here new events that were generated after
+ * the kexec image was loaded.
+ */
+static int ima_update_kexec_buffer(struct notifier_block *self,
+ unsigned long action, void *data)
+{
+ int ret;
+
+ if (!kexec_in_progress)
+ return NOTIFY_OK;
+
+ /*
+ * Add content deep in the buffer to show that we can update
+ * all of it.
+ */
+ strcpy(kexec_buffer + 4 * PAGE_SIZE + 10,
+ "Updated kexec buffer contents.");
+
+ ret = kexec_update_segment(kexec_buffer, kexec_buffer_size,
+ kexec_buffer_load_addr, kexec_buffer_size);
+ if (ret)
+ pr_err("Error updating kexec buffer: %d\n", ret);
+
+ return NOTIFY_OK;
+}
+
+struct notifier_block update_buffer_nb = {
+ .notifier_call = ima_update_kexec_buffer,
+};
+
+/*
+ * Called during kexec_file_load so that IMA can add a segment to the kexec
+ * image with the measurement event log for the next kernel.
+ */
+void ima_add_kexec_buffer(struct kimage *image)
+{
+ /* Ask not to checksum the segment, we may have to update it later. */
+ struct kexec_buf kbuf = { .image = image, .buf_align = PAGE_SIZE,
+ .buf_min = 0, .buf_max = ULONG_MAX,
+ .top_down = true, .skip_checksum = true };
+ bool first_kexec_load = kexec_buffer_load_addr == 0;
+ int ret;
+
+ if (!kexec_can_hand_over_buffer())
+ return;
+
+ if (!first_kexec_load)
+ kfree(kexec_buffer);
+
+ /* Create a relatively big buffer, for testing. */
+ kexec_buffer_size = kbuf.bufsz = kbuf.memsz = 5 * PAGE_SIZE;
+ kexec_buffer = kbuf.buffer = kzalloc(kexec_buffer_size, GFP_KERNEL);
+ if (!kexec_buffer) {
+ pr_err("Not enough memory for the kexec measurement buffer.\n");
+ return;
+ }
+
+ /* Add some content for demonstration purposes. */
+ strcpy(kexec_buffer, "Buffer contents at kexec load time.");
+
+ ret = kexec_add_handover_buffer(&kbuf);
+ if (ret) {
+ pr_err("Error passing over kexec measurement buffer.\n");
+ return;
+ }
+ kexec_buffer_load_addr = kbuf.mem;
+
+ if (first_kexec_load)
+ register_reboot_notifier(&update_buffer_nb);
+
+ pr_debug("kexec measurement buffer for the loaded kernel at 0x%lx.\n",
+ kexec_buffer_load_addr);
+}
+#endif /* CONFIG_KEXEC_FILE */
+
struct ima_template_desc *ima_template_desc_current(void)
{
if (!ima_template)
--
1.9.1
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