[PATCH v4 5/9] ima: on soft reboot, save the measurement list
Mimi Zohar
zohar at linux.vnet.ibm.com
Thu Sep 15 04:26:07 PDT 2016
From: Thiago Jung Bauermann <bauerman at linux.vnet.ibm.com>
This patch uses the kexec buffer passing mechanism to pass the
serialized IMA binary_runtime_measurements to the next kernel.
Changelog v4:
- Revert the skip_checksum change. Instead calculate the checksum
with the measurement list segment, on update validate the existing
checksum before re-calulating a new checksum with the updated
measurement list.
Changelog v3:
- Request a kexec segment for storing the measurement list a half page,
not a full page, more than needed for additional measurements.
- Added binary_runtime_size overflow test
- Limit maximum number of pages needed for kexec_segment_size to half
of totalram_pages. (Dave Young)
Changelog v2:
- Fix build issue by defining a stub ima_add_kexec_buffer and stub
struct kimage when CONFIG_IMA=n and CONFIG_IMA_KEXEC=n. (Fenguang Wu)
- removed kexec_add_handover_buffer() checksum argument.
- added skip_checksum member to kexec_buf
- only register reboot notifier once
Changelog v1:
- updated to call IMA functions (Mimi)
- move code from ima_template.c to ima_kexec.c (Mimi)
Signed-off-by: Thiago Jung Bauermann <bauerman at linux.vnet.ibm.com>
Signed-off-by: Mimi Zohar <zohar at linux.vnet.ibm.com>
---
include/linux/ima.h | 12 +++++
kernel/kexec_file.c | 4 ++
security/integrity/ima/ima_kexec.c | 96 ++++++++++++++++++++++++++++++++++++++
3 files changed, 112 insertions(+)
diff --git a/include/linux/ima.h b/include/linux/ima.h
index 0eb7c2e..7f6952f 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_IMA_KEXEC
+extern void ima_add_kexec_buffer(struct kimage *image);
+#endif
+
#else
static inline int ima_bprm_check(struct linux_binprm *bprm)
{
@@ -62,6 +67,13 @@ static inline void ima_post_path_mknod(struct dentry *dentry)
#endif /* CONFIG_IMA */
+#ifndef CONFIG_IMA_KEXEC
+struct kimage;
+
+static inline void ima_add_kexec_buffer(struct kimage *image)
+{}
+#endif
+
#ifdef CONFIG_IMA_APPRAISE
extern void ima_inode_post_setattr(struct dentry *dentry);
extern int ima_inode_setxattr(struct dentry *dentry, const char *xattr_name,
diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index 3acd386..ccdcbfd 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -20,6 +20,7 @@
#include <linux/list.h>
#include <linux/highmem.h>
#include <linux/fs.h>
+#include <linux/ima.h>
#include <crypto/hash.h>
#include <crypto/sha.h>
#include <linux/syscalls.h>
@@ -204,6 +205,9 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd,
return ret;
image->kernel_buf_len = size;
+ /* IMA needs to pass the measurement list to the next kernel. */
+ ima_add_kexec_buffer(image);
+
/* Call arch image probe handlers */
ret = arch_kexec_kernel_image_probe(image, image->kernel_buf,
image->kernel_buf_len);
diff --git a/security/integrity/ima/ima_kexec.c b/security/integrity/ima/ima_kexec.c
index e77ca9d..0abbc8d 100644
--- a/security/integrity/ima/ima_kexec.c
+++ b/security/integrity/ima/ima_kexec.c
@@ -23,6 +23,11 @@
#include "ima.h"
+#ifdef CONFIG_IMA_KEXEC
+/* Physical address of the measurement buffer in the next kernel. */
+static unsigned long kexec_buffer_load_addr;
+static size_t kexec_segment_size;
+
static int ima_dump_measurement_list(unsigned long *buffer_size, void **buffer,
unsigned long segment_size)
{
@@ -75,6 +80,97 @@ out:
}
/*
+ * Called during kexec execute so that IMA can save the measurement list.
+ */
+static int ima_update_kexec_buffer(struct notifier_block *self,
+ unsigned long action, void *data)
+{
+ void *kexec_buffer = NULL;
+ size_t kexec_buffer_size;
+ int ret;
+
+ if (!kexec_in_progress)
+ return NOTIFY_OK;
+
+ kexec_buffer_size = ima_get_binary_runtime_size();
+ if (kexec_buffer_size > kexec_segment_size) {
+ pr_err("Binary measurement list grew too large.\n");
+ goto out;
+ }
+
+ ima_dump_measurement_list(&kexec_buffer_size, &kexec_buffer,
+ kexec_segment_size);
+ if (!kexec_buffer) {
+ pr_err("Not enough memory for the kexec measurement buffer.\n");
+ goto out;
+ }
+ ret = kexec_update_segment(kexec_buffer, kexec_buffer_size,
+ kexec_buffer_load_addr, kexec_segment_size);
+ if (ret)
+ pr_err("Error updating kexec buffer: %d\n", ret);
+out:
+ 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 for the measurement list for the next kernel.
+ */
+void ima_add_kexec_buffer(struct kimage *image)
+{
+ static int registered;
+ struct kexec_buf kbuf = { .image = image, .buf_align = PAGE_SIZE,
+ .buf_min = 0, .buf_max = ULONG_MAX,
+ .top_down = true };
+ unsigned long binary_runtime_size;
+ int ret;
+
+ if (!kexec_can_hand_over_buffer())
+ return;
+
+ /*
+ * Reserve at least an extra half page of memory for additional
+ * measurements between kexec load and execute.
+ */
+ binary_runtime_size = ima_get_binary_runtime_size();
+ if (binary_runtime_size >= ULONG_MAX - PAGE_SIZE)
+ kexec_segment_size = ULONG_MAX;
+ else
+ kexec_segment_size = ALIGN(ima_get_binary_runtime_size() +
+ PAGE_SIZE / 2, PAGE_SIZE);
+ if ((kexec_segment_size == ULONG_MAX) ||
+ ((kexec_segment_size >> PAGE_SHIFT) > totalram_pages / 2)) {
+ pr_err("Binary measurement list too large.\n");
+ return;
+ }
+
+ /* Ask not to checksum the segment, we will update it later. */
+ kbuf.buffer = NULL;
+ kbuf.bufsz = 0;
+ kbuf.memsz = kexec_segment_size;
+ ret = kexec_add_handover_buffer(&kbuf);
+ if (ret) {
+ pr_err("Error passing over kexec measurement buffer.\n");
+ return;
+ }
+ kexec_buffer_load_addr = kbuf.mem;
+
+ pr_debug("kexec measurement buffer for the loaded kernel at 0x%lx.\n",
+ kexec_buffer_load_addr);
+
+ if (registered)
+ return;
+
+ register_reboot_notifier(&update_buffer_nb);
+ registered = 1;
+}
+#endif /* IMA_KEXEC */
+
+/*
* Restore the measurement list from the previous kernel.
*/
void ima_load_kexec_buffer(void)
--
2.1.0
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