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Subject[PATCH 1/3] securityfs: add the ability to support symlinks
Date
Signed-off-by: John Johansen <john.johansen@canonical.com>
Reviewed-by: Seth Arnold <seth.arnold@canonical.com>
---
include/linux/security.h | 12 ++++
security/inode.c | 140 +++++++++++++++++++++++++++++++++++++++++------
2 files changed, 134 insertions(+), 18 deletions(-)

diff --git a/include/linux/security.h b/include/linux/security.h
index 78d8e03be5d3..28e2be5dd6df 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -1645,6 +1645,10 @@ 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 */
@@ -1664,6 +1668,14 @@ static inline struct dentry *securityfs_create_file(const char *name,
return ERR_PTR(-ENODEV);
}

+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)
{}

diff --git a/security/inode.c b/security/inode.c
index 2cb14162ff8d..10c4955d0bed 100644
--- a/security/inode.c
+++ b/security/inode.c
@@ -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 struct tree_descr files[] = {{""}};
+ int error;
+
+ error = simple_fill_super(sb, SECURITYFS_MAGIC, files);
+ if (error)
+ return error;
+
+ sb->s_op = &securityfs_super_operations;

- return simple_fill_super(sb, SECURITYFS_MAGIC, files);
+ 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 @@ struct dentry *securityfs_create_file(const char *name, umode_t mode,
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);

/**
@@ -172,6 +228,54 @@ struct dentry *securityfs_create_dir(const char *name, struct dentry *parent)
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 | S_IRUGO, 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
*
* @dentry: a pointer to a the dentry of the file or directory to be removed.
--
2.11.0
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