Unverified Commit 1146e5a6 authored by Christian Brauner's avatar Christian Brauner
Browse files

ubifs: store cookie in private data 

Store the cookie to detect concurrent seeks on directories in
file->private_data.

Link: https://lore.kernel.org/r/20240830-vfs-file-f_version-v1-17-6d3e4816aa7b@kernel.org


Reviewed-by: default avatarJan Kara <jack@suse.cz>
Reviewed-by: default avatarJeff Layton <jlayton@kernel.org>
Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parent 0bea8287

fs/ubifs/dir.c

+46 −18
Original line number Diff line number Diff line
@@ -555,6 +555,11 @@ static unsigned int vfs_dent_type(uint8_t type) 
	return 0;

}



struct ubifs_dir_data {

	struct ubifs_dent_node *dent;

	u64 cookie;

};



/*

 * The classical Unix view for directory is that it is a linear array of

 * (name, inode number) entries. Linux/VFS assumes this model as well.
@@ -582,6 +587,7 @@ static int ubifs_readdir(struct file *file, struct dir_context *ctx) 
	struct inode *dir = file_inode(file);

	struct ubifs_info *c = dir->i_sb->s_fs_info;

	bool encrypted = IS_ENCRYPTED(dir);

	struct ubifs_dir_data *data = file->private_data;



	dbg_gen("dir ino %lu, f_pos %#llx", dir->i_ino, ctx->pos);
@@ -604,27 +610,27 @@ static int ubifs_readdir(struct file *file, struct dir_context *ctx) 
		fstr_real_len = fstr.len;

	}



	if (file->f_version == 0) {

	if (data->cookie == 0) {

		/*

		 * The file was seek'ed, which means that @file->private_data

		 * The file was seek'ed, which means that @data->dent

		 * is now invalid. This may also be just the first

		 * 'ubifs_readdir()' invocation, in which case

		 * @file->private_data is NULL, and the below code is

		 * @data->dent is NULL, and the below code is

		 * basically a no-op.

		 */

		kfree(file->private_data);

		file->private_data = NULL;

		kfree(data->dent);

		data->dent = NULL;

	}



	/*

	 * 'generic_file_llseek()' unconditionally sets @file->f_version to

	 * zero, and we use this for detecting whether the file was seek'ed.

	 * 'ubifs_dir_llseek()' sets @data->cookie to zero, and we use this

	 * for detecting whether the file was seek'ed.

	 */

	file->f_version = 1;

	data->cookie = 1;



	/* File positions 0 and 1 correspond to "." and ".." */

	if (ctx->pos < 2) {

		ubifs_assert(c, !file->private_data);

		ubifs_assert(c, !data->dent);

		if (!dir_emit_dots(file, ctx)) {

			if (encrypted)

				fscrypt_fname_free_buffer(&fstr);
@@ -641,10 +647,10 @@ static int ubifs_readdir(struct file *file, struct dir_context *ctx) 
		}



		ctx->pos = key_hash_flash(c, &dent->key);

		file->private_data = dent;

		data->dent = dent;

	}



	dent = file->private_data;

	dent = data->dent;

	if (!dent) {

		/*

		 * The directory was seek'ed to and is now readdir'ed.
@@ -658,7 +664,7 @@ static int ubifs_readdir(struct file *file, struct dir_context *ctx) 
			goto out;

		}

		ctx->pos = key_hash_flash(c, &dent->key);

		file->private_data = dent;

		data->dent = dent;

	}



	while (1) {
@@ -701,15 +707,15 @@ static int ubifs_readdir(struct file *file, struct dir_context *ctx) 
			goto out;

		}



		kfree(file->private_data);

		kfree(data->dent);

		ctx->pos = key_hash_flash(c, &dent->key);

		file->private_data = dent;

		data->dent = dent;

		cond_resched();

	}



out:

	kfree(file->private_data);

	file->private_data = NULL;

	kfree(data->dent);

	data->dent = NULL;



	if (encrypted)

		fscrypt_fname_free_buffer(&fstr);
@@ -733,7 +739,10 @@ static int ubifs_readdir(struct file *file, struct dir_context *ctx) 
/* Free saved readdir() state when the directory is closed */

static int ubifs_dir_release(struct inode *dir, struct file *file)

{

	kfree(file->private_data);

	struct ubifs_dir_data *data = file->private_data;



	kfree(data->dent);

	kfree(data);

	file->private_data = NULL;

	return 0;

}
@@ -1712,6 +1721,24 @@ int ubifs_getattr(struct mnt_idmap *idmap, const struct path *path, 
	return 0;

}



static int ubifs_dir_open(struct inode *inode, struct file *file)

{

	struct ubifs_dir_data *data;



	data = kzalloc(sizeof(struct ubifs_dir_data), GFP_KERNEL);

	if (!data)

		return -ENOMEM;

	file->private_data = data;

	return 0;

}



static loff_t ubifs_dir_llseek(struct file *file, loff_t offset, int whence)

{

	struct ubifs_dir_data *data = file->private_data;



	return generic_llseek_cookie(file, offset, whence, &data->cookie);

}



const struct inode_operations ubifs_dir_inode_operations = {

	.lookup      = ubifs_lookup,

	.create      = ubifs_create,
@@ -1732,7 +1759,8 @@ const struct inode_operations ubifs_dir_inode_operations = { 
};



const struct file_operations ubifs_dir_operations = {

	.llseek         = generic_file_llseek,

	.open		= ubifs_dir_open,

	.llseek         = ubifs_dir_llseek,

	.release        = ubifs_dir_release,

	.read           = generic_read_dir,

	.iterate_shared = ubifs_readdir,