Commit 16e1503e authored by Alexander Mikhalitsyn's avatar Alexander Mikhalitsyn Committed by Miklos Szeredi
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fuse: allow idmapped mounts 

Now we have everything in place and we can allow idmapped mounts
by setting the FS_ALLOW_IDMAP flag. Notice that real availability
of idmapped mounts will depend on the fuse daemon. Fuse daemon
have to set FUSE_ALLOW_IDMAP flag in the FUSE_INIT reply.

To discuss:
- we enable idmapped mounts support only if "default_permissions" mode is
enabled, because otherwise we would need to deal with UID/GID mappings in
the userspace side OR provide the userspace with idmapped
req->in.h.uid/req->in.h.gid values which is not something that we probably
want to. Idmapped mounts philosophy is not about faking caller uid/gid.

Some extra links and examples:

- libfuse support
https://github.com/mihalicyn/libfuse/commits/idmap_support

- fuse-overlayfs support:
https://github.com/mihalicyn/fuse-overlayfs/commits/idmap_support

- cephfs-fuse conversion example
https://github.com/mihalicyn/ceph/commits/fuse_idmap

- glusterfs conversion example
https://github.com/mihalicyn/glusterfs/commits/fuse_idmap



Signed-off-by: default avatarAlexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Reviewed-by: default avatarChristian Brauner <brauner@kernel.org>
Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
parent 6d14b185

fs/fuse/inode.c

+9 −3
Original line number Diff line number Diff line
@@ -1348,6 +1348,12 @@ static void process_init_reply(struct fuse_mount *fm, struct fuse_args *args, 
			}

			if (flags & FUSE_NO_EXPORT_SUPPORT)

				fm->sb->s_export_op = &fuse_export_fid_operations;

			if (flags & FUSE_ALLOW_IDMAP) {

				if (fc->default_permissions)

					fm->sb->s_iflags &= ~SB_I_NOIDMAP;

				else

					ok = false;

			}

		} else {

			ra_pages = fc->max_read / PAGE_SIZE;

			fc->no_lock = 1;
@@ -1395,7 +1401,7 @@ void fuse_send_init(struct fuse_mount *fm) 
		FUSE_HANDLE_KILLPRIV_V2 | FUSE_SETXATTR_EXT | FUSE_INIT_EXT |

		FUSE_SECURITY_CTX | FUSE_CREATE_SUPP_GROUP |

		FUSE_HAS_EXPIRE_ONLY | FUSE_DIRECT_IO_ALLOW_MMAP |

		FUSE_NO_EXPORT_SUPPORT | FUSE_HAS_RESEND;

		FUSE_NO_EXPORT_SUPPORT | FUSE_HAS_RESEND | FUSE_ALLOW_IDMAP;

#ifdef CONFIG_FUSE_DAX

	if (fm->fc->dax)

		flags |= FUSE_MAP_ALIGNMENT;
@@ -1985,7 +1991,7 @@ static void fuse_kill_sb_anon(struct super_block *sb) 
static struct file_system_type fuse_fs_type = {

	.owner		= THIS_MODULE,

	.name		= "fuse",

	.fs_flags	= FS_HAS_SUBTYPE | FS_USERNS_MOUNT,

	.fs_flags	= FS_HAS_SUBTYPE | FS_USERNS_MOUNT | FS_ALLOW_IDMAP,

	.init_fs_context = fuse_init_fs_context,

	.parameters	= fuse_fs_parameters,

	.kill_sb	= fuse_kill_sb_anon,
@@ -2006,7 +2012,7 @@ static struct file_system_type fuseblk_fs_type = { 
	.init_fs_context = fuse_init_fs_context,

	.parameters	= fuse_fs_parameters,

	.kill_sb	= fuse_kill_sb_blk,

	.fs_flags	= FS_REQUIRES_DEV | FS_HAS_SUBTYPE,

	.fs_flags	= FS_REQUIRES_DEV | FS_HAS_SUBTYPE | FS_ALLOW_IDMAP,

};

MODULE_ALIAS_FS("fuseblk");

include/uapi/linux/fuse.h

+19 −1
Original line number Diff line number Diff line
@@ -217,6 +217,9 @@ 
 *  - add backing_id to fuse_open_out, add FOPEN_PASSTHROUGH open flag

 *  - add FUSE_NO_EXPORT_SUPPORT init flag

 *  - add FUSE_NOTIFY_RESEND, add FUSE_HAS_RESEND init flag

 *

 *  7.41

 *  - add FUSE_ALLOW_IDMAP

 */



#ifndef _LINUX_FUSE_H
@@ -252,7 +255,7 @@ 
#define FUSE_KERNEL_VERSION 7



/** Minor version number of this interface */

#define FUSE_KERNEL_MINOR_VERSION 40

#define FUSE_KERNEL_MINOR_VERSION 41



/** The node ID of the root inode */

#define FUSE_ROOT_ID 1
@@ -421,6 +424,7 @@ struct fuse_file_lock { 
 * FUSE_NO_EXPORT_SUPPORT: explicitly disable export support

 * FUSE_HAS_RESEND: kernel supports resending pending requests, and the high bit

 *		    of the request ID indicates resend requests

 * FUSE_ALLOW_IDMAP: allow creation of idmapped mounts

 */

#define FUSE_ASYNC_READ		(1 << 0)

#define FUSE_POSIX_LOCKS	(1 << 1)
@@ -466,6 +470,7 @@ struct fuse_file_lock { 


/* Obsolete alias for FUSE_DIRECT_IO_ALLOW_MMAP */

#define FUSE_DIRECT_IO_RELAX	FUSE_DIRECT_IO_ALLOW_MMAP

#define FUSE_ALLOW_IDMAP	(1ULL << 40)



/**

 * CUSE INIT request/reply flags
@@ -984,6 +989,19 @@ struct fuse_fallocate_in { 
 */

#define FUSE_UNIQUE_RESEND (1ULL << 63)



/**

 * This value will be set by the kernel to

 * (struct fuse_in_header).{uid,gid} fields in

 * case when:

 * - fuse daemon enabled FUSE_ALLOW_IDMAP

 * - idmapping information is not available and uid/gid

 *   can not be mapped in accordance with an idmapping.

 *

 * Note: an idmapping information always available

 * for inode creation operations like:

 * FUSE_MKNOD, FUSE_SYMLINK, FUSE_MKDIR, FUSE_TMPFILE,

 * FUSE_CREATE and FUSE_RENAME2 (with RENAME_WHITEOUT).

 */

#define FUSE_INVALID_UIDGID ((uint32_t)(-1))



struct fuse_in_header {