diff mbox series

[v2] security: Introduce LSM_ORDER_LAST and set it for the integrity LSM

Message ID 20230308171119.1784326-1-roberto.sassu@huaweicloud.com (mailing list archive)
State New, archived
Headers show
Series [v2] security: Introduce LSM_ORDER_LAST and set it for the integrity LSM | expand

Commit Message

Roberto Sassu March 8, 2023, 5:11 p.m. UTC 
From: Roberto Sassu <roberto.sassu@huawei.com>

Introduce LSM_ORDER_LAST, to satisfy the requirement of LSMs willing to be
the last, e.g. the 'integrity' LSM, without changing the kernel command
line or configuration.

Also, set this order for the 'integrity' LSM. While not enforced, this is
the only LSM expected to use it.

Similarly to LSM_ORDER_FIRST, LSMs with LSM_ORDER_LAST are always enabled
and put at the end of the LSM list.

Finally, for LSM_ORDER_MUTABLE LSMs, set the found variable to true if an
LSM is found, regardless of its order. In this way, the kernel would not
wrongly report that the LSM is not built-in in the kernel if its order is
LSM_ORDER_LAST.

Fixes: 79f7865d844c ("LSM: Introduce "lsm=" for boottime LSM selection")
Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
---

Changelog

v1:
- Add comment for LSM_ORDER_LAST definition (suggested by Mimi)
- Add Fixes tag (suggested by Mimi)
- Do minor corrections in the commit messages (suggested by Mimi and Stefan)

 include/linux/lsm_hooks.h |  1 +
 security/integrity/iint.c |  1 +
 security/security.c       | 12 +++++++++---
 3 files changed, 11 insertions(+), 3 deletions(-)

Comments

Mimi Zohar March 9, 2023, 12:23 a.m. UTC | #1 
On Wed, 2023-03-08 at 18:11 +0100, Roberto Sassu wrote:
> From: Roberto Sassu <roberto.sassu@huawei.com>
> 
> Introduce LSM_ORDER_LAST, to satisfy the requirement of LSMs willing to be
> the last, e.g. the 'integrity' LSM, without changing the kernel command
> line or configuration.

^needing to be last

> 
> Also, set this order for the 'integrity' LSM. While not enforced, this is
> the only LSM expected to use it.
> 
> Similarly to LSM_ORDER_FIRST, LSMs with LSM_ORDER_LAST are always enabled
> and put at the end of the LSM list.
> 
> Finally, for LSM_ORDER_MUTABLE LSMs, set the found variable to true if an
> LSM is found, regardless of its order. In this way, the kernel would not
> wrongly report that the LSM is not built-in in the kernel if its order is
> LSM_ORDER_LAST.
> 
> Fixes: 79f7865d844c ("LSM: Introduce "lsm=" for boottime LSM selection")
> Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>

Thanks, Roberto.  With this patch, 'integrity' can be safely removed
from CONFIG_LSM definitions.
Roberto Sassu March 9, 2023, 7:55 a.m. UTC | #2 
On Wed, 2023-03-08 at 19:23 -0500, Mimi Zohar wrote:
> On Wed, 2023-03-08 at 18:11 +0100, Roberto Sassu wrote:
> > From: Roberto Sassu <roberto.sassu@huawei.com>
> > 
> > Introduce LSM_ORDER_LAST, to satisfy the requirement of LSMs willing to be
> > the last, e.g. the 'integrity' LSM, without changing the kernel command
> > line or configuration.
> 
> ^needing to be last

Ok.

> > Also, set this order for the 'integrity' LSM. While not enforced, this is
> > the only LSM expected to use it.
> > 
> > Similarly to LSM_ORDER_FIRST, LSMs with LSM_ORDER_LAST are always enabled
> > and put at the end of the LSM list.
> > 
> > Finally, for LSM_ORDER_MUTABLE LSMs, set the found variable to true if an
> > LSM is found, regardless of its order. In this way, the kernel would not
> > wrongly report that the LSM is not built-in in the kernel if its order is
> > LSM_ORDER_LAST.
> > 
> > Fixes: 79f7865d844c ("LSM: Introduce "lsm=" for boottime LSM selection")
> > Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
> 
> Thanks, Roberto.  With this patch, 'integrity' can be safely removed
> from CONFIG_LSM definitions.

Perfect, will add the new patch.

Thanks

Roberto
diff mbox series

Patch

diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 6e156d2acff..c55761d93a2 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -1716,6 +1716,7 @@  extern void security_add_hooks(struct security_hook_list *hooks, int count,
 enum lsm_order {
 	LSM_ORDER_FIRST = -1,	/* This is only for capabilities. */
 	LSM_ORDER_MUTABLE = 0,
+	LSM_ORDER_LAST = 1,	/* This is only for integrity. */
 };
 
 struct lsm_info {
diff --git a/security/integrity/iint.c b/security/integrity/iint.c
index 8638976f799..b97eb59e0e3 100644
--- a/security/integrity/iint.c
+++ b/security/integrity/iint.c
@@ -182,6 +182,7 @@  static int __init integrity_iintcache_init(void)
 DEFINE_LSM(integrity) = {
 	.name = "integrity",
 	.init = integrity_iintcache_init,
+	.order = LSM_ORDER_LAST,
 };
 
 
diff --git a/security/security.c b/security/security.c
index cf6cc576736..2f36229d5b6 100644
--- a/security/security.c
+++ b/security/security.c
@@ -284,9 +284,9 @@  static void __init ordered_lsm_parse(const char *order, const char *origin)
 		bool found = false;
 
 		for (lsm = __start_lsm_info; lsm < __end_lsm_info; lsm++) {
-			if (lsm->order == LSM_ORDER_MUTABLE &&
-			    strcmp(lsm->name, name) == 0) {
-				append_ordered_lsm(lsm, origin);
+			if (strcmp(lsm->name, name) == 0) {
+				if (lsm->order == LSM_ORDER_MUTABLE)
+					append_ordered_lsm(lsm, origin);
 				found = true;
 			}
 		}
@@ -306,6 +306,12 @@  static void __init ordered_lsm_parse(const char *order, const char *origin)
 		}
 	}
 
+	/* LSM_ORDER_LAST is always last. */
+	for (lsm = __start_lsm_info; lsm < __end_lsm_info; lsm++) {
+		if (lsm->order == LSM_ORDER_LAST)
+			append_ordered_lsm(lsm, "   last");
+	}
+
 	/* Disable all LSMs not in the ordered list. */
 	for (lsm = __start_lsm_info; lsm < __end_lsm_info; lsm++) {
 		if (exists_ordered_lsm(lsm))