ima: fallback to MODULE_SIG_ENFORCE for existing kernel module syscall

The new kernel module syscall appraises kernel modules based
on policy.   If the IMA policy requires kernel module checking,
fallback to module signature enforcing for the existing syscall.
Without CONFIG_MODULE_SIG_FORCE enabled, the kernel module's
integrity is unknown, return -EACCES.

Changelog v1:
- Fix ima_module_check() return result (Tetsuo Handa)

Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reviewed-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Mimi Zohar <zohar@us.ibm.com>

3 files changed, 11 insertions, 5 deletions

diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index 3b2adb794f1..079a85dc37b 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -139,6 +139,7 @@ void ima_delete_rules(void);
 /* Appraise integrity measurements */
 #define IMA_APPRAISE_ENFORCE    0x01
 #define IMA_APPRAISE_FIX        0x02
+#define IMA_APPRAISE_MODULES    0x04
 
 #ifdef CONFIG_IMA_APPRAISE
 int ima_appraise_measurement(struct integrity_iint_cache *iint,
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index 45de18e9a6f..dba965de90d 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -291,11 +291,15 @@ EXPORT_SYMBOL_GPL(ima_file_check);
  */
 int ima_module_check(struct file *file)
 {
-        int rc;
+        int rc = 0;
 
-        if (!file)
-                rc = INTEGRITY_UNKNOWN;
-        else
+        if (!file) {
+                if (ima_appraise & IMA_APPRAISE_MODULES) {
+#ifndef CONFIG_MODULE_SIG_FORCE
+                        rc = -EACCES;   /* INTEGRITY_UNKNOWN */
+#endif
+                }
+        } else
                 rc = process_measurement(file, file->f_dentry->d_name.name,
                                          MAY_EXEC, MODULE_CHECK);
         return (ima_appraise & IMA_APPRAISE_ENFORCE) ? rc : 0;
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index af7d182d5a4..479fca940bb 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -523,7 +523,8 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
         }
         if (!result && (entry->action == UNKNOWN))
                 result = -EINVAL;
-
+        else if (entry->func == MODULE_CHECK)
+                ima_appraise |= IMA_APPRAISE_MODULES;
         audit_log_format(ab, "res=%d", !result);
         audit_log_end(ab);
         return result;