[RFC PATCH v3 2/9] [squash] do not store entry for SECSID_NULL

[Ondrej Mosnacek <omosnace@xxxxxxxxxx>]

This patch is kept separate only for review. Eventually it will be
folded into the previous patch.

Signed-off-by: Ondrej Mosnacek <omosnace@xxxxxxxxxx>
---
 security/selinux/ss/policydb.c |  2 +-
 security/selinux/ss/sidtab.c   | 25 ++++++++++++++++---------
 security/selinux/ss/sidtab.h   |  3 ++-
 3 files changed, 19 insertions(+), 11 deletions(-)

diff --git a/security/selinux/ss/policydb.c b/security/selinux/ss/policydb.c
index 59359fa0bd74..a50d625e7946 100644
--- a/security/selinux/ss/policydb.c
+++ b/security/selinux/ss/policydb.c
@@ -912,7 +912,7 @@ int policydb_load_isids(struct policydb *p, struct sidtab *s)
 			sidtab_destroy(s);
 			goto out;
 		}
-		if (c->sid[0] > SECINITSID_NUM) {
+		if (c->sid[0] == SECSID_NULL || c->sid[0] > SECINITSID_NUM) {
 			pr_err("SELinux:  Initial SID %s out of range.\n",
 				c->u.name);
 			sidtab_destroy(s);
diff --git a/security/selinux/ss/sidtab.c b/security/selinux/ss/sidtab.c
index fd8115b211a6..e157d8240cf1 100644
--- a/security/selinux/ss/sidtab.c
+++ b/security/selinux/ss/sidtab.c
@@ -23,7 +23,7 @@ int sidtab_init(struct sidtab *s)
 	if (!s->htable)
 		return -ENOMEM;
 
-	for (i = 0; i <= SECINITSID_NUM; i++)
+	for (i = 0; i < SECINITSID_NUM; i++)
 		s->isids[i].set = 0;
 
 	for (i = 0; i < SIDTAB_SIZE; i++)
@@ -86,8 +86,15 @@ static int sidtab_insert(struct sidtab *s, u32 sid, struct context *context)
 
 int sidtab_set_initial(struct sidtab *s, u32 sid, struct context *context)
 {
-	struct sidtab_isid_entry *entry = &s->isids[sid];
-	int rc = context_cpy(&entry->context, context);
+	struct sidtab_isid_entry *entry;
+	int rc;
+
+	if (sid == 0 || sid > SECINITSID_NUM)
+		return -EINVAL;
+
+	entry = &s->isids[sid - 1];
+
+	rc = context_cpy(&entry->context, context);
 	if (rc)
 		return rc;
 
@@ -116,19 +123,19 @@ static struct context *sidtab_search_core(struct sidtab *s, u32 sid, int force)
 	struct context *context;
 	struct sidtab_isid_entry *entry;
 
-	if (!s)
+	if (!s || sid == 0)
 		return NULL;
 
 	if (sid > SECINITSID_NUM) {
 		context = sidtab_lookup(s, sid - (SECINITSID_NUM + 1));
 	} else {
-		entry = &s->isids[sid];
+		entry = &s->isids[sid - 1];
 		context = entry->set ? &entry->context : NULL;
 	}
 	if (context && (!context->len || force))
 		return context;
 
-	entry = &s->isids[SECINITSID_UNLABELED];
+	entry = &s->isids[SECINITSID_UNLABELED - 1];
 	return entry->set ? &entry->context : NULL;
 }
 
@@ -283,11 +290,11 @@ int sidtab_context_to_sid(struct sidtab *s, struct context *context, u32 *sid)
 	int rc;
 	u32 i;
 
-	for (i = 0; i <= SECINITSID_NUM; i++) {
+	for (i = 0; i < SECINITSID_NUM; i++) {
 		struct sidtab_isid_entry *entry = &s->isids[i];
 
 		if (entry->set && context_cmp(context, &entry->context)) {
-			*sid = i;
+			*sid = i + 1;
 			return 0;
 		}
 	}
@@ -334,7 +341,7 @@ void sidtab_destroy(struct sidtab *s)
 	if (!s)
 		return;
 
-	for (i = 0; i <= SECINITSID_NUM; i++)
+	for (i = 0; i < SECINITSID_NUM; i++)
 		if (s->isids[i].set)
 			context_destroy(&s->isids[i].context);
 
diff --git a/security/selinux/ss/sidtab.h b/security/selinux/ss/sidtab.h
index dc0a80bc8894..e657ae6bf996 100644
--- a/security/selinux/ss/sidtab.h
+++ b/security/selinux/ss/sidtab.h
@@ -36,7 +36,8 @@ struct sidtab {
 	struct sidtab_node *cache[SIDTAB_CACHE_LEN];
 	spinlock_t lock;
 
-	struct sidtab_isid_entry isids[SECINITSID_NUM + 1];
+	/* index == SID - 1 (no entry for SECSID_NULL) */
+	struct sidtab_isid_entry isids[SECINITSID_NUM];
 };
 
 int sidtab_init(struct sidtab *s);
-- 
2.19.2