Re: [Linux-ima-devel] [PATCH v6 07/10] ima: store the builtin/custom template definitions in a list

From: Mimi Zohar <redacted>

The builtin and single custom templates are currently stored in an
array.  In preparation for being able to restore a measurement list
containing multiple builtin/custom templates, this patch stores the
builtin and custom templates as a linked list.  This will permit
defining more than one custom template per boot.

Changelog v4:
- fix "spinlock bad magic" BUG - reported by Dmitry Vyukov

Changelog v3:
- initialize template format list in ima_template_desc_current(), as it
might be called during __setup before normal initialization. (kernel
test robot)
- remove __init annotation of ima_init_template_list()

Changelog v2:
- fix lookup_template_desc() preemption imbalance (kernel test robot)

Signed-off-by: Mimi Zohar <redacted>
---
 security/integrity/ima/ima.h          |  2 ++
 security/integrity/ima/ima_main.c     |  1 +
 security/integrity/ima/ima_template.c | 52 +++++++++++++++++++++++++++--------
 3 files changed, 44 insertions(+), 11 deletions(-)

diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index 139dec67dcbf..6b0540ad189f 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h

@@ -85,6 +85,7 @@ struct ima_template_field {

 /* IMA template descriptor definition */
 struct ima_template_desc {
+       struct list_head list;
        char *name;
        char *fmt;
        int num_fields;

@@ -146,6 +147,7 @@ int ima_restore_measurement_list(loff_t bufsize, void *buf);
 int ima_measurements_show(struct seq_file *m, void *v);
 unsigned long ima_get_binary_runtime_size(void);
 int ima_init_template(void);
+void ima_init_template_list(void);

 /*
  * used to protect h_table and sha_table

diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index 423d111b3b94..50818c60538b 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c

@@ -418,6 +418,7 @@ static int __init init_ima(void)
 {
        int error;

+       ima_init_template_list();
        hash_setup(CONFIG_IMA_DEFAULT_HASH);
        error = ima_init();
        if (!error) {

diff --git a/security/integrity/ima/ima_template.c b/security/integrity/ima/ima_template.c
index 37f972cb05fe..c0d808c20c40 100644
--- a/security/integrity/ima/ima_template.c
+++ b/security/integrity/ima/ima_template.c

@@ -15,16 +15,20 @@

 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

+#include <linux/rculist.h>
 #include "ima.h"
 #include "ima_template_lib.h"

-static struct ima_template_desc defined_templates[] = {
+static struct ima_template_desc builtin_templates[] = {
        {.name = IMA_TEMPLATE_IMA_NAME, .fmt = IMA_TEMPLATE_IMA_FMT},
        {.name = "ima-ng", .fmt = "d-ng|n-ng"},
        {.name = "ima-sig", .fmt = "d-ng|n-ng|sig"},
        {.name = "", .fmt = ""},        /* placeholder for a custom format */
 };

+static LIST_HEAD(defined_templates);
+static DEFINE_SPINLOCK(template_list);
+
 static struct ima_template_field supported_fields[] = {
        {.field_id = "d", .field_init = ima_eventdigest_init,
         .field_show = ima_show_template_digest},

@@ -53,6 +57,8 @@ static int __init ima_template_setup(char *str)
        if (ima_template)
                return 1;

+       ima_init_template_list();
+
        /*
         * Verify that a template with the supplied name exists.
         * If not, use CONFIG_IMA_DEFAULT_TEMPLATE.

@@ -81,7 +87,7 @@ __setup("ima_template=", ima_template_setup);

 static int __init ima_template_fmt_setup(char *str)
 {
-       int num_templates = ARRAY_SIZE(defined_templates);
+       int num_templates = ARRAY_SIZE(builtin_templates);

        if (ima_template)
                return 1;

@@ -92,22 +98,28 @@ static int __init ima_template_fmt_setup(char *str)
                return 1;
        }

-       defined_templates[num_templates - 1].fmt = str;
-       ima_template = defined_templates + num_templates - 1;
+       builtin_templates[num_templates - 1].fmt = str;
+       ima_template = builtin_templates + num_templates - 1;
+
        return 1;
 }
 __setup("ima_template_fmt=", ima_template_fmt_setup);

 static struct ima_template_desc *lookup_template_desc(const char *name)
 {
-       int i;
+       struct ima_template_desc *template_desc;
+       int found = 0;

-       for (i = 0; i < ARRAY_SIZE(defined_templates); i++) {
-               if (strcmp(defined_templates[i].name, name) == 0)
-                       return defined_templates + i;
+       rcu_read_lock();
+       list_for_each_entry_rcu(template_desc, &defined_templates, list) {
+               if ((strcmp(template_desc->name, name) == 0) ||
+                   (strcmp(template_desc->fmt, name) == 0)) {
+                       found = 1;
+                       break;
+               }
        }
-
-       return NULL;
+       rcu_read_unlock();
+       return found ? template_desc : NULL;
 }

 static struct ima_template_field *lookup_template_field(const char *field_id)

@@ -183,11 +195,29 @@ static int template_desc_init_fields(const char *template_fmt,
        return 0;
 }

+void ima_init_template_list(void)
+{
+       int i;
+
+       if (!list_empty(&defined_templates))
+               return;
+
+       spin_lock(&template_list);
+       for (i = 0; i < ARRAY_SIZE(builtin_templates); i++) {
+               list_add_tail_rcu(&builtin_templates[i].list,
+                                 &defined_templates);
+       }
+       spin_unlock(&template_list);
+       synchronize_rcu();