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 phylosophy 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 Cc: Christian Brauner <brauner@xxxxxxxxxx> Cc: Seth Forshee <sforshee@xxxxxxxxxx> Cc: Miklos Szeredi <miklos@xxxxxxxxxx> Cc: Amir Goldstein <amir73il@xxxxxxxxx> Cc: Bernd Schubert <bschubert@xxxxxxx> Cc: <linux-fsdevel@xxxxxxxxxxxxxxx> Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@xxxxxxxxxxxxx> Reviewed-by: Christian Brauner <brauner@xxxxxxxxxx> --- v2: - simplified and get rid of ->allow_idmap global VFS callback v3: - now use a new SB_I_NOIDMAP flag v4: - small rebase changes --- fs/fuse/inode.c | 12 +++++++++--- include/uapi/linux/fuse.h | 20 +++++++++++++++++++- 2 files changed, 28 insertions(+), 4 deletions(-) diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c index 2e26810066e8..9f9456d3e466 100644 --- a/fs/fuse/inode.c +++ b/fs/fuse/inode.c @@ -1343,6 +1343,12 @@ 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; @@ -1390,7 +1396,7 @@ 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; @@ -1980,7 +1986,7 @@ 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, @@ -2001,7 +2007,7 @@ 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"); diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h index 2ccf38181df2..f1e99458e29e 100644 --- a/include/uapi/linux/fuse.h +++ b/include/uapi/linux/fuse.h @@ -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 { -- 2.34.1
