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author | Linus Torvalds <torvalds@linux-foundation.org> | 2021-08-31 11:54:02 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2021-08-31 11:54:02 -0700 |
commit | 1dd5915a5cbda100e67823e7a4ca7af919185ea6 (patch) | |
tree | b5712c83462c29fc4666ae004b9c3f2d993ee889 /fs | |
parent | 0ee7c3e25d8c28845fceb4dd1c3cb5f50b9c45a9 (diff) | |
parent | 8374f43123a5957326095d108a12c49ae509624f (diff) | |
download | linux-1dd5915a5cbda100e67823e7a4ca7af919185ea6.tar.bz2 |
Merge tag 'fs.move_mount.move_mount_set_group.v5.15' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux
Pull move_mount updates from Christian Brauner:
"This contains an extension to the move_mount() syscall making it
possible to add a single private mount into an existing propagation
tree.
The use-case comes from the criu folks which have been struggling with
restoring complex mount trees for a long time. Variations of this work
have been discussed at Plumbers before, e.g.
https://www.linuxplumbersconf.org/event/7/contributions/640/
The extension to move_mount() enables criu to restore any set of mount
namespaces, mount trees and sharing group trees without introducing
yet more complexity into mount propagation itself.
The changes required to criu to make use of this and restore complex
propagation trees are available at
https://github.com/Snorch/criu/commits/mount-v2-poc
A cleaned-up version of this will go up for merging into the main criu
repo after this lands"
* tag 'fs.move_mount.move_mount_set_group.v5.15' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux:
tests: add move_mount(MOVE_MOUNT_SET_GROUP) selftest
move_mount: allow to add a mount into an existing group
Diffstat (limited to 'fs')
-rw-r--r-- | fs/namespace.c | 77 |
1 files changed, 76 insertions, 1 deletions
diff --git a/fs/namespace.c b/fs/namespace.c index 20caa4b4c539..12852363d90e 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -2694,6 +2694,78 @@ out: return ret; } +static int do_set_group(struct path *from_path, struct path *to_path) +{ + struct mount *from, *to; + int err; + + from = real_mount(from_path->mnt); + to = real_mount(to_path->mnt); + + namespace_lock(); + + err = -EINVAL; + /* To and From must be mounted */ + if (!is_mounted(&from->mnt)) + goto out; + if (!is_mounted(&to->mnt)) + goto out; + + err = -EPERM; + /* We should be allowed to modify mount namespaces of both mounts */ + if (!ns_capable(from->mnt_ns->user_ns, CAP_SYS_ADMIN)) + goto out; + if (!ns_capable(to->mnt_ns->user_ns, CAP_SYS_ADMIN)) + goto out; + + err = -EINVAL; + /* To and From paths should be mount roots */ + if (from_path->dentry != from_path->mnt->mnt_root) + goto out; + if (to_path->dentry != to_path->mnt->mnt_root) + goto out; + + /* Setting sharing groups is only allowed across same superblock */ + if (from->mnt.mnt_sb != to->mnt.mnt_sb) + goto out; + + /* From mount root should be wider than To mount root */ + if (!is_subdir(to->mnt.mnt_root, from->mnt.mnt_root)) + goto out; + + /* From mount should not have locked children in place of To's root */ + if (has_locked_children(from, to->mnt.mnt_root)) + goto out; + + /* Setting sharing groups is only allowed on private mounts */ + if (IS_MNT_SHARED(to) || IS_MNT_SLAVE(to)) + goto out; + + /* From should not be private */ + if (!IS_MNT_SHARED(from) && !IS_MNT_SLAVE(from)) + goto out; + + if (IS_MNT_SLAVE(from)) { + struct mount *m = from->mnt_master; + + list_add(&to->mnt_slave, &m->mnt_slave_list); + to->mnt_master = m; + } + + if (IS_MNT_SHARED(from)) { + to->mnt_group_id = from->mnt_group_id; + list_add(&to->mnt_share, &from->mnt_share); + lock_mount_hash(); + set_mnt_shared(to); + unlock_mount_hash(); + } + + err = 0; +out: + namespace_unlock(); + return err; +} + static int do_move_mount(struct path *old_path, struct path *new_path) { struct mnt_namespace *ns; @@ -3678,7 +3750,10 @@ SYSCALL_DEFINE5(move_mount, if (ret < 0) goto out_to; - ret = do_move_mount(&from_path, &to_path); + if (flags & MOVE_MOUNT_SET_GROUP) + ret = do_set_group(&from_path, &to_path); + else + ret = do_move_mount(&from_path, &to_path); out_to: path_put(&to_path); |