[3/3] Make LSM Writable Hooks a command line option

Commit Message

Igor Stoppa July 10, 2017, 3:06 p.m. UTC

This patch shows how it is possible to take advantage of pmalloc:
instead of using the build-time option __lsm_ro_after_init, to decide if
it is possible to keep the hooks modifiable, now this becomes a
boot-time decision, based on the kernel command line.

This patch relies on:

"Convert security_hook_heads into explicit array of struct list_head"
Author: Tetsuo Handa <[e-mail]>

to break free from the static constraint imposed by the previous
hardening model, based on __ro_after_init.

The default value is disabled, unless SE Linux debugging is turned on.

Signed-off-by: Igor Stoppa <[e-mail]>
CC: Tetsuo Handa <[e-mail]>
---
 security/security.c | 22 +++++++++++++++++++---
 1 file changed, 19 insertions(+), 3 deletions(-)

Comments

kernel test robot July 11, 2017, 4:12 a.m. UTC | #1

Hi Igor,

[auto build test ERROR on linus/master]
[cannot apply to v4.12]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Igor-Stoppa/mm-security-ro-protection-for-dynamic-data/20170711-084116
config: score-spct6600_defconfig (attached as .config)
compiler: score-elf-gcc (GCC) 4.9.1 20140622 (prerelease)
reproduce:
        wget https://raw.githubusercontent.com/01org/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        make.cross ARCH=score 

All errors (new ones prefixed by >>):

   security/security.o: In function `security_init':
>> security.c:(.init.text+0x68): undefined reference to `pmalloc_create_pool'
>> security.c:(.init.text+0x98): undefined reference to `pmalloc'
>> security.c:(.init.text+0x150): undefined reference to `pmalloc_protect_pool'

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

Patch

diff --git a/security/security.c b/security/security.c
index 44c47b6..c7b4670 100644
--- a/security/security.c
+++ b/security/security.c
@@ -27,6 +27,7 @@ 
 #include <linux/personality.h>
 #include <linux/backing-dev.h>
 #include <linux/string.h>
+#include <linux/pmalloc.h>
 #include <net/flow.h>
 
 #define MAX_LSM_EVM_XATTR	2
@@ -34,10 +35,19 @@ 
 /* Maximum number of letters for an LSM name string */
 #define SECURITY_NAME_MAX	10
 
-static struct list_head hook_heads[LSM_MAX_HOOK_INDEX]
-	__lsm_ro_after_init;
 static ATOMIC_NOTIFIER_HEAD(lsm_notifier_chain);
 
+static int dynamic_lsm = IS_ENABLED(CONFIG_SECURITY_SELINUX_DISABLE);
+
+static __init int set_dynamic_lsm(char *str)
+{
+	get_option(&str, &dynamic_lsm);
+	return 0;
+}
+early_param("dynamic_lsm", set_dynamic_lsm);
+
+static struct list_head *hook_heads;
+static struct gen_pool *sec_pool;
 char *lsm_names;
 /* Boot-time LSM user choice */
 static __initdata char chosen_lsm[SECURITY_NAME_MAX + 1] =
@@ -62,6 +72,11 @@  int __init security_init(void)
 {
 	enum security_hook_index i;
 
+	sec_pool = pmalloc_create_pool("security", PMALLOC_DEFAULT_ALLOC_ORDER);
+	BUG_ON(!sec_pool);
+	hook_heads = pmalloc(sec_pool,
+			     sizeof(struct list_head) * LSM_MAX_HOOK_INDEX);
+	BUG_ON(!hook_heads);
 	for (i = 0; i < LSM_MAX_HOOK_INDEX; i++)
 		INIT_LIST_HEAD(&hook_heads[i]);
 	pr_info("Security Framework initialized\n");
@@ -77,7 +92,8 @@  int __init security_init(void)
 	 * Load all the remaining security modules.
 	 */
 	do_security_initcalls();
-
+	if (!dynamic_lsm)
+		pmalloc_protect_pool(sec_pool);
 	return 0;
 }