linux/fs/9p/xattr.c

// SPDX-License-Identifier: LGPL-2.1
/*
 * Copyright IBM Corporation, 2010
 * Author Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
 */

#include <linux/module.h>
#include <linux/fs.h>
#include <linux/sched.h>
#include <linux/uio.h>
#include <linux/posix_acl_xattr.h>
#include <net/9p/9p.h>
#include <net/9p/client.h>

#include "fid.h"
#include "xattr.h"

ssize_t v9fs_fid_xattr_get(struct p9_fid *fid, const char *name,
			   void *buffer, size_t buffer_size)
{
	ssize_t retval;
	u64 attr_size;
	struct p9_fid *attr_fid;
	struct kvec kvec = {.iov_base = buffer, .iov_len = buffer_size};
	struct iov_iter to;
	int err;

	iov_iter_kvec(&to, ITER_DEST, &kvec, 1, buffer_size);

	attr_fid = p9_client_xattrwalk(fid, name, &attr_size);
	if (IS_ERR(attr_fid)) {
		retval = PTR_ERR(attr_fid);
		p9_debug(P9_DEBUG_VFS, "p9_client_attrwalk failed %zd\n",
			 retval);
		return retval;
	}
	if (attr_size > buffer_size) {
		if (buffer_size)
			retval = -ERANGE;
		else if (attr_size > SSIZE_MAX)
			retval = -EOVERFLOW;
		else /* request to get the attr_size */
			retval = attr_size;
	} else {
		iov_iter_truncate(&to, attr_size);
		retval = p9_client_read(attr_fid, 0, &to, &err);
		if (err)
			retval = err;
	}
	p9_fid_put(attr_fid);
	return retval;
}


/*
 * v9fs_xattr_get()
 *
 * Copy an extended attribute into the buffer
 * provided, or compute the buffer size required.
 * Buffer is NULL to compute the size of the buffer required.
 *
 * Returns a negative error number on failure, or the number of bytes
 * used / required on success.
 */
ssize_t v9fs_xattr_get(struct dentry *dentry, const char *name,
		       void *buffer, size_t buffer_size)
{
	struct p9_fid *fid;
	int ret;

	p9_debug(P9_DEBUG_VFS, "name = '%s' value_len = %zu\n",
		 name, buffer_size);
	fid = v9fs_fid_lookup(dentry);
	if (IS_ERR(fid))
		return PTR_ERR(fid);
	ret = v9fs_fid_xattr_get(fid, name, buffer, buffer_size);
	p9_fid_put(fid);

	return ret;
}

/*
 * v9fs_xattr_set()
 *
 * Create, replace or remove an extended attribute for this inode. Buffer
 * is NULL to remove an existing extended attribute, and non-NULL to
 * either replace an existing extended attribute, or create a new extended
 * attribute. The flags XATTR_REPLACE and XATTR_CREATE
 * specify that an extended attribute must exist and must not exist
 * previous to the call, respectively.
 *
 * Returns 0, or a negative error number on failure.
 */
int v9fs_xattr_set(struct dentry *dentry, const char *name,
		   const void *value, size_t value_len, int flags)
{
	int ret;
	struct p9_fid *fid;

	fid  = v9fs_fid_lookup(dentry);
	if (IS_ERR(fid))
		return PTR_ERR(fid);
	ret = v9fs_fid_xattr_set(fid, name, value, value_len, flags);
	p9_fid_put(fid);
	return ret;
}

int v9fs_fid_xattr_set(struct p9_fid *fid, const char *name,
		   const void *value, size_t value_len, int flags)
{
	struct kvec kvec = {.iov_base = (void *)value, .iov_len = value_len};
	struct iov_iter from;
	int retval, err;

	iov_iter_kvec(&from, ITER_SOURCE, &kvec, 1, value_len);

	p9_debug(P9_DEBUG_VFS, "name = %s value_len = %zu flags = %d\n",
		 name, value_len, flags);

	/* Clone it */
	fid = clone_fid(fid);
	if (IS_ERR(fid))
		return PTR_ERR(fid);

	/*
	 * On success fid points to xattr
	 */
	retval = p9_client_xattrcreate(fid, name, value_len, flags);
	if (retval < 0)
		p9_debug(P9_DEBUG_VFS, "p9_client_xattrcreate failed %d\n",
			 retval);
	else
		p9_client_write(fid, 0, &from, &retval);
	err = p9_fid_put(fid);
	if (!retval && err)
		retval = err;
	return retval;
}

ssize_t v9fs_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
{
	/* Txattrwalk with an empty string lists xattrs instead */
	return v9fs_xattr_get(dentry, "", buffer, buffer_size);
}

static int v9fs_xattr_handler_get(const struct xattr_handler *handler,
				  struct dentry *dentry, struct inode *inode,
				  const char *name, void *buffer, size_t size)
{
	const char *full_name = xattr_full_name(handler, name);

	return v9fs_xattr_get(dentry, full_name, buffer, size);
}

static int v9fs_xattr_handler_set(const struct xattr_handler *handler,
				  struct mnt_idmap *idmap,
				  struct dentry *dentry, struct inode *inode,
				  const char *name, const void *value,
				  size_t size, int flags)
{
	const char *full_name = xattr_full_name(handler, name);

	return v9fs_xattr_set(dentry, full_name, value, size, flags);
}

static const struct xattr_handler v9fs_xattr_user_handler = {
	.prefix	= XATTR_USER_PREFIX,
	.get	= v9fs_xattr_handler_get,
	.set	= v9fs_xattr_handler_set,
};

static const struct xattr_handler v9fs_xattr_trusted_handler = {
	.prefix	= XATTR_TRUSTED_PREFIX,
	.get	= v9fs_xattr_handler_get,
	.set	= v9fs_xattr_handler_set,
};

#ifdef CONFIG_9P_FS_SECURITY
static const struct xattr_handler v9fs_xattr_security_handler = {
	.prefix	= XATTR_SECURITY_PREFIX,
	.get	= v9fs_xattr_handler_get,
	.set	= v9fs_xattr_handler_set,
};
#endif

const struct xattr_handler * const v9fs_xattr_handlers[] = {
	&v9fs_xattr_user_handler,
	&v9fs_xattr_trusted_handler,
#ifdef CONFIG_9P_FS_SECURITY
	&v9fs_xattr_security_handler,
#endif
	NULL
};