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securityfs: add the ability to support symlinks 

Signed-off-by: John Johansen <john.johansen@canonical.com>
Reviewed-by: Seth Arnold <seth.arnold@canonical.com>
Acked-by: Kees Cook <keescook@chromium.org>
This commit is contained in:
John Johansen 2017-05-07 05:53:37 -07:00
parent 4227c333f6
commit 6623ec7c4d
2 changed files with 135 additions and 21 deletions
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12
include/linux/security.h
View File

@ -1651,6 +1651,10 @@ extern struct dentry *securityfs_create_file(const char *name, umode_t mode,
struct dentry *parent, void *data,
const struct file_operations *fops);
extern struct dentry *securityfs_create_dir(const char *name, struct dentry *parent);
struct dentry *securityfs_create_symlink(const char *name,
struct dentry *parent,
const char *target,
const struct inode_operations *iops);
extern void securityfs_remove(struct dentry *dentry);
#else /* CONFIG_SECURITYFS */
@ -1670,6 +1674,14 @@ static inline struct dentry *securityfs_create_file(const char *name,
return ERR_PTR(-ENODEV);
}
static inline struct dentry *securityfs_create_symlink(const char *name,
struct dentry *parent,
const char *target,
const struct inode_operations *iops)
{
return ERR_PTR(-ENODEV);
}
static inline void securityfs_remove(struct dentry *dentry)
{}

144
security/inode.c
View File

@ -26,11 +26,31 @@
static struct vfsmount *mount;
static int mount_count;
static void securityfs_evict_inode(struct inode *inode)
{
truncate_inode_pages_final(&inode->i_data);
clear_inode(inode);
if (S_ISLNK(inode->i_mode))
kfree(inode->i_link);
}
static const struct super_operations securityfs_super_operations = {
.statfs = simple_statfs,
.evict_inode = securityfs_evict_inode,
};
static int fill_super(struct super_block *sb, void *data, int silent)
{
static const struct tree_descr files[] = {{""}};
int error;
return simple_fill_super(sb, SECURITYFS_MAGIC, files);
error = simple_fill_super(sb, SECURITYFS_MAGIC, files);
if (error)
return error;
sb->s_op = &securityfs_super_operations;
return 0;
}
static struct dentry *get_sb(struct file_system_type *fs_type,
@ -48,7 +68,7 @@ static struct file_system_type fs_type = {
};
/**
* securityfs_create_file - create a file in the securityfs filesystem
* securityfs_create_dentry - create a dentry in the securityfs filesystem
*
* @name: a pointer to a string containing the name of the file to create.
* @mode: the permission that the file should have
@ -60,34 +80,35 @@ static struct file_system_type fs_type = {
* the open() call.
* @fops: a pointer to a struct file_operations that should be used for
* this file.
* @iops: a point to a struct of inode_operations that should be used for
* this file/dir
*
* This is the basic "create a file" function for securityfs. It allows for a
* wide range of flexibility in creating a file, or a directory (if you
* want to create a directory, the securityfs_create_dir() function is
* recommended to be used instead).
* This is the basic "create a file/dir/symlink" function for
* securityfs. It allows for a wide range of flexibility in creating
* a file, or a directory (if you want to create a directory, the
* securityfs_create_dir() function is recommended to be used
* instead).
*
* This function returns a pointer to a dentry if it succeeds. This
* pointer must be passed to the securityfs_remove() function when the file is
* to be removed (no automatic cleanup happens if your module is unloaded,
* you are responsible here). If an error occurs, the function will return
* the error value (via ERR_PTR).
* pointer must be passed to the securityfs_remove() function when the
* file is to be removed (no automatic cleanup happens if your module
* is unloaded, you are responsible here). If an error occurs, the
* function will return the error value (via ERR_PTR).
*
* If securityfs is not enabled in the kernel, the value %-ENODEV is
* returned.
*/
struct dentry *securityfs_create_file(const char *name, umode_t mode,
struct dentry *parent, void *data,
const struct file_operations *fops)
static struct dentry *securityfs_create_dentry(const char *name, umode_t mode,
struct dentry *parent, void *data,
const struct file_operations *fops,
const struct inode_operations *iops)
{
struct dentry *dentry;
int is_dir = S_ISDIR(mode);
struct inode *dir, *inode;
int error;
if (!is_dir) {
BUG_ON(!fops);
if (!(mode & S_IFMT))
mode = (mode & S_IALLUGO) | S_IFREG;
}
pr_debug("securityfs: creating file '%s'\n",name);
@ -120,11 +141,14 @@ struct dentry *securityfs_create_file(const char *name, umode_t mode,
inode->i_mode = mode;
inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
inode->i_private = data;
if (is_dir) {
if (S_ISDIR(mode)) {
inode->i_op = &simple_dir_inode_operations;
inode->i_fop = &simple_dir_operations;
inc_nlink(inode);
inc_nlink(dir);
} else if (S_ISLNK(mode)) {
inode->i_op = iops ? iops : &simple_symlink_inode_operations;
inode->i_link = data;
} else {
inode->i_fop = fops;
}
@ -141,6 +165,38 @@ out:
simple_release_fs(&mount, &mount_count);
return dentry;
}
/**
* securityfs_create_file - create a file in the securityfs filesystem
*
* @name: a pointer to a string containing the name of the file to create.
* @mode: the permission that the file should have
* @parent: a pointer to the parent dentry for this file. This should be a
* directory dentry if set. If this parameter is %NULL, then the
* file will be created in the root of the securityfs filesystem.
* @data: a pointer to something that the caller will want to get to later
* on. The inode.i_private pointer will point to this value on
* the open() call.
* @fops: a pointer to a struct file_operations that should be used for
* this file.
*
* This function creates a file in securityfs with the given @name.
*
* This function returns a pointer to a dentry if it succeeds. This
* pointer must be passed to the securityfs_remove() function when the file is
* to be removed (no automatic cleanup happens if your module is unloaded,
* you are responsible here). If an error occurs, the function will return
* the error value (via ERR_PTR).
*
* If securityfs is not enabled in the kernel, the value %-ENODEV is
* returned.
*/
struct dentry *securityfs_create_file(const char *name, umode_t mode,
struct dentry *parent, void *data,
const struct file_operations *fops)
{
return securityfs_create_dentry(name, mode, parent, data, fops, NULL);
}
EXPORT_SYMBOL_GPL(securityfs_create_file);
/**
@ -165,12 +221,58 @@ EXPORT_SYMBOL_GPL(securityfs_create_file);
*/
struct dentry *securityfs_create_dir(const char *name, struct dentry *parent)
{
return securityfs_create_file(name,
S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
parent, NULL, NULL);
return securityfs_create_file(name, S_IFDIR | 0755, parent, NULL, NULL);
}
EXPORT_SYMBOL_GPL(securityfs_create_dir);
/**
* securityfs_create_symlink - create a symlink in the securityfs filesystem
*
* @name: a pointer to a string containing the name of the symlink to
* create.
* @parent: a pointer to the parent dentry for the symlink. This should be a
* directory dentry if set. If this parameter is %NULL, then the
* directory will be created in the root of the securityfs filesystem.
* @target: a pointer to a string containing the name of the symlink's target.
* If this parameter is %NULL, then the @iops parameter needs to be
* setup to handle .readlink and .get_link inode_operations.
* @iops: a pointer to the struct inode_operations to use for the symlink. If
* this parameter is %NULL, then the default simple_symlink_inode
* operations will be used.
*
* This function creates a symlink in securityfs with the given @name.
*
* This function returns a pointer to a dentry if it succeeds. This
* pointer must be passed to the securityfs_remove() function when the file is
* to be removed (no automatic cleanup happens if your module is unloaded,
* you are responsible here). If an error occurs, the function will return
* the error value (via ERR_PTR).
*
* If securityfs is not enabled in the kernel, the value %-ENODEV is
* returned.
*/
struct dentry *securityfs_create_symlink(const char *name,
struct dentry *parent,
const char *target,
const struct inode_operations *iops)
{
struct dentry *dent;
char *link = NULL;
if (target) {
link = kstrdup(target, GFP_KERNEL);
if (!link)
return ERR_PTR(-ENOMEM);
}
dent = securityfs_create_dentry(name, S_IFLNK | 0444, parent,
link, NULL, iops);
if (IS_ERR(dent))
kfree(link);
return dent;
}
EXPORT_SYMBOL_GPL(securityfs_create_symlink);
/**
* securityfs_remove - removes a file or directory from the securityfs filesystem
*