selinux: introduce security_context_str_to_sid

There seems to be a little confusion as to whether the scontext_len
parameter of security_context_to_sid() includes the nul-byte or
not. Reading security_context_to_sid_core(), it seems that the
expectation is that it does not (both the string copying and the test
for scontext_len being zero hint at that).

Introduce the helper security_context_str_to_sid() to do the strlen()
call and fix all callers.
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <pmoore@redhat.com>

security/selinux/hooks.c

@@ -674,10 +674,9 @@ static int selinux_set_mnt_opts(struct super_block *sb,
 
 		if (flags[i] == SBLABEL_MNT)
 			continue;
-		rc = security_context_to_sid(mount_options[i],
-					     strlen(mount_options[i]), &sid, GFP_KERNEL);
+		rc = security_context_str_to_sid(mount_options[i], &sid, GFP_KERNEL);
 		if (rc) {
-			printk(KERN_WARNING "SELinux: security_context_to_sid"
+			printk(KERN_WARNING "SELinux: security_context_str_to_sid"
 			       "(%s) failed for (dev %s, type %s) errno=%d\n",
 			       mount_options[i], sb->s_id, name, rc);
 			goto out;
@@ -2617,15 +2616,12 @@ static int selinux_sb_remount(struct super_block *sb, void *data)
 
 	for (i = 0; i < opts.num_mnt_opts; i++) {
 		u32 sid;
-		size_t len;
 
 		if (flags[i] == SBLABEL_MNT)
 			continue;
-		len = strlen(mount_options[i]);
-		rc = security_context_to_sid(mount_options[i], len, &sid,
-					     GFP_KERNEL);
+		rc = security_context_str_to_sid(mount_options[i], &sid, GFP_KERNEL);
 		if (rc) {
-			printk(KERN_WARNING "SELinux: security_context_to_sid"
+			printk(KERN_WARNING "SELinux: security_context_str_to_sid"
 			       "(%s) failed for (dev %s, type %s) errno=%d\n",
 			       mount_options[i], sb->s_id, sb->s_type->name, rc);
 			goto out_free_opts;

security/selinux/include/security.h

@@ -166,6 +166,8 @@ int security_sid_to_context_force(u32 sid, char **scontext, u32 *scontext_len);
 int security_context_to_sid(const char *scontext, u32 scontext_len,
 			    u32 *out_sid, gfp_t gfp);
 
+int security_context_str_to_sid(const char *scontext, u32 *out_sid, gfp_t gfp);
+
 int security_context_to_sid_default(const char *scontext, u32 scontext_len,
 				    u32 *out_sid, u32 def_sid, gfp_t gfp_flags);
 

security/selinux/selinuxfs.c

@@ -731,13 +731,11 @@ static ssize_t sel_write_access(struct file *file, char *buf, size_t size)
 	if (sscanf(buf, "%s %s %hu", scon, tcon, &tclass) != 3)
 		goto out;
 
-	length = security_context_to_sid(scon, strlen(scon) + 1, &ssid,
-					 GFP_KERNEL);
+	length = security_context_str_to_sid(scon, &ssid, GFP_KERNEL);
 	if (length)
 		goto out;
 
-	length = security_context_to_sid(tcon, strlen(tcon) + 1, &tsid,
-					 GFP_KERNEL);
+	length = security_context_str_to_sid(tcon, &tsid, GFP_KERNEL);
 	if (length)
 		goto out;
 
@@ -819,13 +817,11 @@ static ssize_t sel_write_create(struct file *file, char *buf, size_t size)
 		objname = namebuf;
 	}
 
-	length = security_context_to_sid(scon, strlen(scon) + 1, &ssid,
-					 GFP_KERNEL);
+	length = security_context_str_to_sid(scon, &ssid, GFP_KERNEL);
 	if (length)
 		goto out;
 
-	length = security_context_to_sid(tcon, strlen(tcon) + 1, &tsid,
-					 GFP_KERNEL);
+	length = security_context_str_to_sid(tcon, &tsid, GFP_KERNEL);
 	if (length)
 		goto out;
 
@@ -882,13 +878,11 @@ static ssize_t sel_write_relabel(struct file *file, char *buf, size_t size)
 	if (sscanf(buf, "%s %s %hu", scon, tcon, &tclass) != 3)
 		goto out;
 
-	length = security_context_to_sid(scon, strlen(scon) + 1, &ssid,
-					 GFP_KERNEL);
+	length = security_context_str_to_sid(scon, &ssid, GFP_KERNEL);
 	if (length)
 		goto out;
 
-	length = security_context_to_sid(tcon, strlen(tcon) + 1, &tsid,
-					 GFP_KERNEL);
+	length = security_context_str_to_sid(tcon, &tsid, GFP_KERNEL);
 	if (length)
 		goto out;
 
@@ -940,7 +934,7 @@ static ssize_t sel_write_user(struct file *file, char *buf, size_t size)
 	if (sscanf(buf, "%s %s", con, user) != 2)
 		goto out;
 
-	length = security_context_to_sid(con, strlen(con) + 1, &sid, GFP_KERNEL);
+	length = security_context_str_to_sid(con, &sid, GFP_KERNEL);
 	if (length)
 		goto out;
 
@@ -1000,13 +994,11 @@ static ssize_t sel_write_member(struct file *file, char *buf, size_t size)
 	if (sscanf(buf, "%s %s %hu", scon, tcon, &tclass) != 3)
 		goto out;
 
-	length = security_context_to_sid(scon, strlen(scon) + 1, &ssid,
-					 GFP_KERNEL);
+	length = security_context_str_to_sid(scon, &ssid, GFP_KERNEL);
 	if (length)
 		goto out;
 
-	length = security_context_to_sid(tcon, strlen(tcon) + 1, &tsid,
-					 GFP_KERNEL);
+	length = security_context_str_to_sid(tcon, &tsid, GFP_KERNEL);
 	if (length)
 		goto out;
 

security/selinux/ss/services.c

@@ -1476,6 +1476,11 @@ int security_context_to_sid(const char *scontext, u32 scontext_len, u32 *sid,
 					    sid, SECSID_NULL, gfp, 0);
 }
 
+int security_context_str_to_sid(const char *scontext, u32 *sid, gfp_t gfp)
+{
+	return security_context_to_sid(scontext, strlen(scontext), sid, gfp);
+}
+
 /**
  * security_context_to_sid_default - Obtain a SID for a given security context,
  * falling back to specified default if needed.