linux-kernel - [PATCH v2 5/9] selinux: services: update type for number of class permissions

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Message-Id: <20230728155501.39632-4-cgzones@googlemail.com>
Date:   Fri, 28 Jul 2023 17:54:55 +0200
From:   Christian Göttsche <cgzones@...glemail.com>
To:     selinux@...r.kernel.org
Cc:     Paul Moore <paul@...l-moore.com>,
        Stephen Smalley <stephen.smalley.work@...il.com>,
        Eric Paris <eparis@...isplace.org>,
        Ondrej Mosnacek <omosnace@...hat.com>,
        "GONG, Ruiqi" <gongruiqi1@...wei.com>, linux-kernel@...r.kernel.org
Subject: [PATCH v2 5/9] selinux: services: update type for number of class permissions

Security classes have only up to 32 permissions, hence using an u16 is
sufficient (while improving padding in struct selinux_mapping).

Also use a fixed sized cast in a bit shift to avoid (well defined)
overflows on architectures where sizeof(unsigned int) != sizeof(u32)
resulting in no bits set.

Signed-off-by: Christian Göttsche <cgzones@...glemail.com>
---
v2:
   update commit description:
     - mention struct selinux_mapping  in the padding argument
       (currently between the first and second member there are 2 bytes
        padding)
     - mention overflow in the cast argument and the result of setting
       no bits due to it
---
 security/selinux/ss/services.c | 6 +++---
 security/selinux/ss/services.h | 2 +-
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c
index 2c5be06fbada..cf4b87ec4a0e 100644
--- a/security/selinux/ss/services.c
+++ b/security/selinux/ss/services.c
@@ -97,7 +97,6 @@ static int selinux_set_mapping(struct policydb *pol,
 			       struct selinux_map *out_map)
 {
 	u16 i, j;
-	unsigned k;
 	bool print_unknown_handle = false;
 
 	/* Find number of classes in the input mapping */
@@ -117,6 +116,7 @@ static int selinux_set_mapping(struct policydb *pol,
 	while (map[j].name) {
 		const struct security_class_mapping *p_in = map + (j++);
 		struct selinux_mapping *p_out = out_map->mapping + j;
+		u16 k;
 
 		/* An empty class string skips ahead */
 		if (!strcmp(p_in->name, "")) {
@@ -202,7 +202,7 @@ static void map_decision(struct selinux_map *map,
 {
 	if (tclass < map->size) {
 		struct selinux_mapping *mapping = &map->mapping[tclass];
-		unsigned int i, n = mapping->num_perms;
+		u16 i, n = mapping->num_perms;
 		u32 result;
 
 		for (i = 0, result = 0; i < n; i++) {
@@ -230,7 +230,7 @@ static void map_decision(struct selinux_map *map,
 		 * should audit that denial
 		 */
 		for (; i < (sizeof(u32)*8); i++)
-			result |= 1<<i;
+			result |= 1<<((u32)i);
 		avd->auditdeny = result;
 	}
 }
diff --git a/security/selinux/ss/services.h b/security/selinux/ss/services.h
index ed2ee6600467..d24b0a3d198e 100644
--- a/security/selinux/ss/services.h
+++ b/security/selinux/ss/services.h
@@ -12,7 +12,7 @@
 /* Mapping for a single class */
 struct selinux_mapping {
 	u16 value; /* policy value for class */
-	unsigned int num_perms; /* number of permissions in class */
+	u16 num_perms; /* number of permissions in class */
 	u32 perms[sizeof(u32) * 8]; /* policy values for permissions */
 };
 
-- 
2.40.1