selinux: add selinuxfs structure for object class discovery

The structure is as follows (relative to selinuxfs root):

/class/file/index
/class/file/perms/read
/class/file/perms/write
...

Each class is allocated 33 inodes, 1 for the class index and 32 for
permissions.  Relative to SEL_CLASS_INO_OFFSET, the inode of the index file
DIV 33 is the class number.  The inode of the permission file % 33 is the
index of the permission for that class.

Signed-off-by: Christopher J. PeBenito <cpebenito@tresys.com>
Signed-off-by: James Morris <jmorris@namei.org>

2 files changed, 250 insertions, 0 deletions

diff --git a/security/selinux/include/security.h b/security/selinux/include/security.h
index 731a173f5a5f..83bdd4d2a29e 100644
--- a/security/selinux/include/security.h
+++ b/security/selinux/include/security.h
@@ -41,6 +41,7 @@ extern int selinux_mls_enabled;
 
 int security_load_policy(void * data, size_t len);
 
+#define SEL_VEC_MAX 32
 struct av_decision {
         u32 allowed;
         u32 decided;
diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
index cf1acde778de..c9e92daedee2 100644
--- a/security/selinux/selinuxfs.c
+++ b/security/selinux/selinuxfs.c
@@ -67,6 +67,10 @@ static struct dentry *bool_dir = NULL;
 static int bool_num = 0;
 static int *bool_pending_values = NULL;
 
+/* global data for classes */
+static struct dentry *class_dir = NULL;
+static unsigned long last_class_ino;
+
 extern void selnl_notify_setenforce(int val);
 
 /* Check whether a task is allowed to use a security operation. */
@@ -106,6 +110,7 @@ static unsigned long sel_last_ino = SEL_INO_NEXT - 1;
 
 #define SEL_INITCON_INO_OFFSET  0x01000000
 #define SEL_BOOL_INO_OFFSET     0x02000000
+#define SEL_CLASS_INO_OFFSET    0x04000000
 #define SEL_INO_MASK            0x00ffffff
 
 #define TMPBUFLEN       12
@@ -237,6 +242,11 @@ static const struct file_operations sel_policyvers_ops = {
 
 /* declaration for sel_write_load */
 static int sel_make_bools(void);
+static int sel_make_classes(void);
+
+/* declaration for sel_make_class_dirs */
+static int sel_make_dir(struct inode *dir, struct dentry *dentry,
+                        unsigned long *ino);
 
 static ssize_t sel_read_mls(struct file *filp, char __user *buf,
                                 size_t count, loff_t *ppos)
@@ -287,10 +297,18 @@ static ssize_t sel_write_load(struct file * file, const char __user * buf,
                 goto out;
 
         ret = sel_make_bools();
+        if (ret) {
+                length = ret;
+                goto out1;
+        }
+
+        ret = sel_make_classes();
         if (ret)
                 length = ret;
         else
                 length = count;
+
+out1:
         audit_log(current->audit_context, GFP_KERNEL, AUDIT_MAC_POLICY_LOAD,
                 "policy loaded auid=%u",
                 audit_get_loginuid(current->audit_context));
@@ -1293,6 +1311,225 @@ out:
         return ret;
 }
 
+static inline unsigned int sel_div(unsigned long a, unsigned long b)
+{
+        return a / b - (a % b < 0);
+}
+
+static inline unsigned long sel_class_to_ino(u16 class)
+{
+        return (class * (SEL_VEC_MAX + 1)) | SEL_CLASS_INO_OFFSET;
+}
+
+static inline u16 sel_ino_to_class(unsigned long ino)
+{
+        return sel_div(ino & SEL_INO_MASK, SEL_VEC_MAX + 1);
+}
+
+static inline unsigned long sel_perm_to_ino(u16 class, u32 perm)
+{
+        return (class * (SEL_VEC_MAX + 1) + perm) | SEL_CLASS_INO_OFFSET;
+}
+
+static inline u32 sel_ino_to_perm(unsigned long ino)
+{
+        return (ino & SEL_INO_MASK) % (SEL_VEC_MAX + 1);
+}
+
+static ssize_t sel_read_class(struct file * file, char __user *buf,
+                                size_t count, loff_t *ppos)
+{
+        ssize_t rc, len;
+        char *page;
+        unsigned long ino = file->f_path.dentry->d_inode->i_ino;
+
+        page = (char *)__get_free_page(GFP_KERNEL);
+        if (!page) {
+                rc = -ENOMEM;
+                goto out;
+        }
+
+        len = snprintf(page, PAGE_SIZE, "%d", sel_ino_to_class(ino));
+        rc = simple_read_from_buffer(buf, count, ppos, page, len);
+        free_page((unsigned long)page);
+out:
+        return rc;
+}
+
+static const struct file_operations sel_class_ops = {
+        .read           = sel_read_class,
+};
+
+static ssize_t sel_read_perm(struct file * file, char __user *buf,
+                                size_t count, loff_t *ppos)
+{
+        ssize_t rc, len;
+        char *page;
+        unsigned long ino = file->f_path.dentry->d_inode->i_ino;
+
+        page = (char *)__get_free_page(GFP_KERNEL);
+        if (!page) {
+                rc = -ENOMEM;
+                goto out;
+        }
+
+        len = snprintf(page, PAGE_SIZE,"%d", sel_ino_to_perm(ino));
+        rc = simple_read_from_buffer(buf, count, ppos, page, len);
+        free_page((unsigned long)page);
+out:
+        return rc;
+}
+
+static const struct file_operations sel_perm_ops = {
+        .read           = sel_read_perm,
+};
+
+static int sel_make_perm_files(char *objclass, int classvalue,
+                                struct dentry *dir)
+{
+        int i, rc = 0, nperms;
+        char **perms;
+
+        rc = security_get_permissions(objclass, &perms, &nperms);
+        if (rc)
+                goto out;
+
+        for (i = 0; i < nperms; i++) {
+                struct inode *inode;
+                struct dentry *dentry;
+
+                dentry = d_alloc_name(dir, perms[i]);
+                if (!dentry) {
+                        rc = -ENOMEM;
+                        goto out1;
+                }
+
+                inode = sel_make_inode(dir->d_sb, S_IFREG|S_IRUGO);
+                if (!inode) {
+                        rc = -ENOMEM;
+                        goto out1;
+                }
+                inode->i_fop = &sel_perm_ops;
+                /* i+1 since perm values are 1-indexed */
+                inode->i_ino = sel_perm_to_ino(classvalue, i+1);
+                d_add(dentry, inode);
+        }
+
+out1:
+        for (i = 0; i < nperms; i++)
+                kfree(perms[i]);
+        kfree(perms);
+out:
+        return rc;
+}
+
+static int sel_make_class_dir_entries(char *classname, int index,
+                                        struct dentry *dir)
+{
+        struct dentry *dentry = NULL;
+        struct inode *inode = NULL;
+        int rc;
+
+        dentry = d_alloc_name(dir, "index");
+        if (!dentry) {
+                rc = -ENOMEM;
+                goto out;
+        }
+
+        inode = sel_make_inode(dir->d_sb, S_IFREG|S_IRUGO);
+        if (!inode) {
+                rc = -ENOMEM;
+                goto out;
+        }
+
+        inode->i_fop = &sel_class_ops;
+        inode->i_ino = sel_class_to_ino(index);
+        d_add(dentry, inode);
+
+        dentry = d_alloc_name(dir, "perms");
+        if (!dentry) {
+                rc = -ENOMEM;
+                goto out;
+        }
+
+        rc = sel_make_dir(dir->d_inode, dentry, &last_class_ino);
+        if (rc)
+                goto out;
+
+        rc = sel_make_perm_files(classname, index, dentry);
+
+out:
+        return rc;
+}
+
+static void sel_remove_classes(void)
+{
+        struct list_head *class_node;
+
+        list_for_each(class_node, &class_dir->d_subdirs) {
+                struct dentry *class_subdir = list_entry(class_node,
+                                        struct dentry, d_u.d_child);
+                struct list_head *class_subdir_node;
+
+                list_for_each(class_subdir_node, &class_subdir->d_subdirs) {
+                        struct dentry *d = list_entry(class_subdir_node,
+                                                struct dentry, d_u.d_child);
+
+                        if (d->d_inode)
+                                if (d->d_inode->i_mode & S_IFDIR)
+                                        sel_remove_entries(d);
+                }
+
+                sel_remove_entries(class_subdir);
+        }
+
+        sel_remove_entries(class_dir);
+}
+
+static int sel_make_classes(void)
+{
+        int rc = 0, nclasses, i;
+        char **classes;
+
+        /* delete any existing entries */
+        sel_remove_classes();
+
+        rc = security_get_classes(&classes, &nclasses);
+        if (rc < 0)
+                goto out;
+
+        /* +2 since classes are 1-indexed */
+        last_class_ino = sel_class_to_ino(nclasses+2);
+
+        for (i = 0; i < nclasses; i++) {
+                struct dentry *class_name_dir;
+
+                class_name_dir = d_alloc_name(class_dir, classes[i]);
+                if (!class_name_dir) {
+                        rc = -ENOMEM;
+                        goto out1;
+                }
+
+                rc = sel_make_dir(class_dir->d_inode, class_name_dir,
+                                &last_class_ino);
+                if (rc)
+                        goto out1;
+
+                /* i+1 since class values are 1-indexed */
+                rc = sel_make_class_dir_entries(classes[i], i+1,
+                                class_name_dir);
+                if (rc)
+                        goto out1;
+        }
+
+out1:
+        for (i = 0; i < nclasses; i++)
+                kfree(classes[i]);
+        kfree(classes);
+out:
+        return rc;
+}
+
 static int sel_make_dir(struct inode *dir, struct dentry *dentry,
                         unsigned long *ino)
 {
@@ -1407,6 +1644,18 @@ static int sel_fill_super(struct super_block * sb, void * data, int silent)
         if (ret)
                 goto err;
 
+        dentry = d_alloc_name(sb->s_root, "class");
+        if (!dentry) {
+                ret = -ENOMEM;
+                goto err;
+        }
+
+        ret = sel_make_dir(root_inode, dentry, &sel_last_ino);
+        if (ret)
+                goto err;
+
+        class_dir = dentry;
+
 out:
         return ret;
 err: