Re: [PATCH 4/4] selinux: add selinuxfs structure for object class discovery

On Wed, 2007-05-23 at 09:12 -0400, Christopher J. PeBenito wrote:
> From: Christopher J. PeBenito <cpebenito@tresys.com>
>
> 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>

For all four patches:
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>

>
> ---
> security/selinux/include/security.h | 1 +
> security/selinux/selinuxfs.c | 249 +++++++++++++++++++++++++++++++++++
> 2 files changed, 250 insertions(+), 0 deletions(-)
>
> diff --git a/security/selinux/include/security.h b/security/selinux/include/security.h
> index 731a173..83bdd4d 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 95051b1..8be9706 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:

-- 
Stephen Smalley
National Security Agency


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