tomoyo: Add a kernel config option for fuzzing testing.

syzbot is reporting kernel panic triggered by memory allocation fault
injection before loading TOMOYO's policy [1]. To make the fuzzing tests
useful, we need to assign a profile other than "disabled" (no-op) mode.
Therefore, let's allow syzbot to load TOMOYO's built-in policy for
"learning" mode using a kernel config option. This option must not be
enabled for kernels built for production system, for this option also
disables domain/program checks when modifying policy configuration via
/sys/kernel/security/tomoyo/ interface.

[1] https://syzkaller.appspot.com/bug?extid=29569ed06425fcf67a95

Reported-by: syzbot <syzbot+e1b8084e532b6ee7afab@syzkaller.appspotmail.com>
Reported-by: syzbot <syzbot+29569ed06425fcf67a95@syzkaller.appspotmail.com>
Reported-by: syzbot <syzbot+2ee3f8974c2e7dc69feb@syzkaller.appspotmail.com>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: James Morris <jamorris@linux.microsoft.com>

2 files changed, 22 insertions, 1 deletions

diff --git a/security/tomoyo/Kconfig b/security/tomoyo/Kconfig
index 404dce66952a..a00ab7eb6181 100644
--- a/security/tomoyo/Kconfig
+++ b/security/tomoyo/Kconfig
@@ -74,3 +74,13 @@ config SECURITY_TOMOYO_ACTIVATION_TRIGGER
           You can override this setting via TOMOYO_trigger= kernel command line
           option. For example, if you pass init=/bin/systemd option, you may
           want to also pass TOMOYO_trigger=/bin/systemd option.
+
+config SECURITY_TOMOYO_INSECURE_BUILTIN_SETTING
+        bool "Use insecure built-in settings for fuzzing tests."
+        default n
+        depends on SECURITY_TOMOYO
+        select SECURITY_TOMOYO_OMIT_USERSPACE_LOADER
+        help
+          Enabling this option forces minimal built-in policy and disables
+          domain/program checks for run-time policy modifications. Please enable
+          this option only if this kernel is built for doing fuzzing tests.
diff --git a/security/tomoyo/common.c b/security/tomoyo/common.c
index 57988d95d33d..dd3d5942e669 100644
--- a/security/tomoyo/common.c
+++ b/security/tomoyo/common.c
@@ -940,7 +940,7 @@ static bool tomoyo_manager(void)
         const char *exe;
         const struct task_struct *task = current;
         const struct tomoyo_path_info *domainname = tomoyo_domain()->domainname;
-        bool found = false;
+        bool found = IS_ENABLED(CONFIG_SECURITY_TOMOYO_INSECURE_BUILTIN_SETTING);
 
         if (!tomoyo_policy_loaded)
                 return true;
@@ -2810,6 +2810,16 @@ void tomoyo_check_profile(void)
  */
 void __init tomoyo_load_builtin_policy(void)
 {
+#ifdef CONFIG_SECURITY_TOMOYO_INSECURE_BUILTIN_SETTING
+        static char tomoyo_builtin_profile[] __initdata =
+                "PROFILE_VERSION=20150505\n"
+                "0-CONFIG={ mode=learning grant_log=no reject_log=yes }\n";
+        static char tomoyo_builtin_exception_policy[] __initdata =
+                "aggregator proc:/self/exe /proc/self/exe\n";
+        static char tomoyo_builtin_domain_policy[] __initdata = "";
+        static char tomoyo_builtin_manager[] __initdata = "";
+        static char tomoyo_builtin_stat[] __initdata = "";
+#else
         /*
          * This include file is manually created and contains built-in policy
          * named "tomoyo_builtin_profile", "tomoyo_builtin_exception_policy",
@@ -2817,6 +2827,7 @@ void __init tomoyo_load_builtin_policy(void)
          * "tomoyo_builtin_stat" in the form of "static char [] __initdata".
          */
 #include "builtin-policy.h"
+#endif
         u8 i;
         const int idx = tomoyo_read_lock();