ima: maintain memory size needed for serializing the measurement list

In preparation for serializing the binary_runtime_measurements, this
patch maintains the amount of memory required.

Link: http://lkml.kernel.org/r/1480554346-29071-5-git-send-email-zohar@linux.vnet.ibm.com
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
Acked-by: Dmitry Kasatkin <dmitry.kasatkin@gmail.com>
Cc: Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Andreas Steffen <andreas.steffen@strongswan.org>
Cc: Josh Sklar <sklar@linux.vnet.ibm.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Stewart Smith <stewart@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 64 insertions, 2 deletions

diff --git a/security/integrity/ima/Kconfig b/security/integrity/ima/Kconfig
index 5487827fa86c..370eb2f4dd37 100644
--- a/security/integrity/ima/Kconfig
+++ b/security/integrity/ima/Kconfig
@@ -27,6 +27,18 @@ config IMA
           to learn more about IMA.
           If unsure, say N.
 
+config IMA_KEXEC
+        bool "Enable carrying the IMA measurement list across a soft boot"
+        depends on IMA && TCG_TPM && HAVE_IMA_KEXEC
+        default n
+        help
+           TPM PCRs are only reset on a hard reboot.  In order to validate
+           a TPM's quote after a soft boot, the IMA measurement list of the
+           running kernel must be saved and restored on boot.
+
+           Depending on the IMA policy, the measurement list can grow to
+           be very large.
+
 config IMA_MEASURE_PCR_IDX
         int
         depends on IMA
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index 51dc8d57d64d..ea1dcc452911 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -143,6 +143,7 @@ void ima_print_digest(struct seq_file *m, u8 *digest, u32 size);
 struct ima_template_desc *ima_template_desc_current(void);
 int ima_restore_measurement_entry(struct ima_template_entry *entry);
 int ima_restore_measurement_list(loff_t bufsize, void *buf);
+unsigned long ima_get_binary_runtime_size(void);
 int ima_init_template(void);
 
 /*
diff --git a/security/integrity/ima/ima_queue.c b/security/integrity/ima/ima_queue.c
index e180de598a92..d9aa5ab71204 100644
--- a/security/integrity/ima/ima_queue.c
+++ b/security/integrity/ima/ima_queue.c
@@ -29,6 +29,11 @@
 #define AUDIT_CAUSE_LEN_MAX 32
 
 LIST_HEAD(ima_measurements);    /* list of all measurements */
+#ifdef CONFIG_IMA_KEXEC
+static unsigned long binary_runtime_size;
+#else
+static unsigned long binary_runtime_size = ULONG_MAX;
+#endif
 
 /* key: inode (before secure-hashing a file) */
 struct ima_h_table ima_htable = {
@@ -64,6 +69,24 @@ static struct ima_queue_entry *ima_lookup_digest_entry(u8 *digest_value,
         return ret;
 }
 
+/*
+ * Calculate the memory required for serializing a single
+ * binary_runtime_measurement list entry, which contains a
+ * couple of variable length fields (e.g template name and data).
+ */
+static int get_binary_runtime_size(struct ima_template_entry *entry)
+{
+        int size = 0;
+
+        size += sizeof(u32);    /* pcr */
+        size += sizeof(entry->digest);
+        size += sizeof(int);    /* template name size field */
+        size += strlen(entry->template_desc->name) + 1;
+        size += sizeof(entry->template_data_len);
+        size += entry->template_data_len;
+        return size;
+}
+
 /* ima_add_template_entry helper function:
  * - Add template entry to the measurement list and hash table, for
  *   all entries except those carried across kexec.
@@ -91,9 +114,30 @@ static int ima_add_digest_entry(struct ima_template_entry *entry,
                 key = ima_hash_key(entry->digest);
                 hlist_add_head_rcu(&qe->hnext, &ima_htable.queue[key]);
         }
+
+        if (binary_runtime_size != ULONG_MAX) {
+                int size;
+
+                size = get_binary_runtime_size(entry);
+                binary_runtime_size = (binary_runtime_size < ULONG_MAX - size) ?
+                     binary_runtime_size + size : ULONG_MAX;
+        }
         return 0;
 }
 
+/*
+ * Return the amount of memory required for serializing the
+ * entire binary_runtime_measurement list, including the ima_kexec_hdr
+ * structure.
+ */
+unsigned long ima_get_binary_runtime_size(void)
+{
+        if (binary_runtime_size >= (ULONG_MAX - sizeof(struct ima_kexec_hdr)))
+                return ULONG_MAX;
+        else
+                return binary_runtime_size + sizeof(struct ima_kexec_hdr);
+};
+
 static int ima_pcr_extend(const u8 *hash, int pcr)
 {
         int result = 0;
@@ -107,8 +151,13 @@ static int ima_pcr_extend(const u8 *hash, int pcr)
         return result;
 }
 
-/* Add template entry to the measurement list and hash table,
- * and extend the pcr.
+/*
+ * Add template entry to the measurement list and hash table, and
+ * extend the pcr.
+ *
+ * On systems which support carrying the IMA measurement list across
+ * kexec, maintain the total memory size required for serializing the
+ * binary_runtime_measurements.
  */
 int ima_add_template_entry(struct ima_template_entry *entry, int violation,
                            const char *op, struct inode *inode,