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Subject[PATCH security-next v5 29/30] LSM: Introduce enum lsm_order
Date
In preparation for distinguishing the "capability" LSM from other LSMs, it
must be ordered first. This introduces LSM_ORDER_MUTABLE for the general
LSMs and LSM_ORDER_FIRST for capability. In the future LSM_ORDER_LAST
for could be added for anything that must run last (e.g. Landlock may
use this).

Signed-off-by: Kees Cook <keescook@chromium.org>
---
include/linux/lsm_hooks.h | 6 ++++++
security/security.c | 9 ++++++++-
2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 833ec0f03795..97898679a505 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -2042,8 +2042,14 @@ extern void security_add_hooks(struct security_hook_list *hooks, int count,
#define LSM_FLAG_LEGACY_MAJOR BIT(0)
#define LSM_FLAG_EXCLUSIVE BIT(1)

+enum lsm_order {
+ LSM_ORDER_FIRST = -1, /* This is only for capabilities. */
+ LSM_ORDER_MUTABLE = 0,
+};
+
struct lsm_info {
const char *name; /* Required. */
+ enum lsm_order order; /* Optional: default is LSM_ORDER_MUTABLE */
unsigned long flags; /* Optional: flags describing LSM */
int *enabled; /* Optional: controlled by CONFIG_LSM */
int (*init)(void); /* Required. */
diff --git a/security/security.c b/security/security.c
index 2eb8afdd945d..004938eb8e70 100644
--- a/security/security.c
+++ b/security/security.c
@@ -174,6 +174,12 @@ static void __init ordered_lsm_parse(const char *order, const char *origin)
struct lsm_info *lsm;
char *sep, *name, *next;

+ /* LSM_ORDER_FIRST is always first. */
+ for (lsm = __start_lsm_info; lsm < __end_lsm_info; lsm++) {
+ if (lsm->order == LSM_ORDER_FIRST)
+ append_ordered_lsm(lsm, "first");
+ }
+
sep = kstrdup(order, GFP_KERNEL);
next = sep;
/* Walk the list, looking for matching LSMs. */
@@ -181,7 +187,8 @@ 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 (strcmp(lsm->name, name) == 0) {
+ if (lsm->order == LSM_ORDER_MUTABLE &&
+ strcmp(lsm->name, name) == 0) {
append_ordered_lsm(lsm, origin);
found = true;
}
--
2.17.1
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