user/sven/linux.git/fs/namespace.c, branch v6.3.3

fs: drop peer group ids under namespace lock

2023-03-31T10:13:37Z

When cleaning up peer group ids in the failure path we need to make sure to hold on to the namespace lock. Otherwise another thread might just turn the mount from a shared into a non-shared mount concurrently. Link: https://lore.kernel.org/lkml/00000000000088694505f8132d77@google.com Fixes: 2a1867219c7b ("fs: add mount_setattr()") Reported-by: syzbot+8ac3859139c685c4f597@syzkaller.appspotmail.com Cc: stable@vger.kernel.org # 5.12+ Message-Id: <20230330-vfs-mount_setattr-propagation-fix-v1-1-37548d91533b@kernel.org> Signed-off-by: Christian Brauner

Merge branch 'work.namespace' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

2023-02-25T03:20:07Z

Pull ipc namespace update from Al Viro: "Rik's patches reducing the amount of synchronize_rcu() triggered by ipc namespace destruction. I've some pending stuff reducing that on the normal umount side, but it's nowhere near ready and Rik's stuff shouldn't be held back due to conflicts - I'll just redo the parts of my series that stray into ipc/*" * 'work.namespace' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: ipc,namespace: batch free ipc_namespace structures ipc,namespace: make ipc namespace allocation wait for pending free

ipc,namespace: batch free ipc_namespace structures

2023-01-28T00:08:00Z

Instead of waiting for an RCU grace period between each ipc_namespace structure that is being freed, wait an RCU grace period for every batch of ipc_namespace structures. Thanks to Al Viro for the suggestion of the helper function. This speeds up the run time of the test case that allocates ipc_namespaces in a loop from 6 minutes, to a little over 1 second: real 0m1.192s user 0m0.038s sys 0m1.152s Signed-off-by: Rik van Riel Reported-by: Chris Mason Tested-by: Giuseppe Scrivano Suggested-by: Al Viro Signed-off-by: Al Viro

fs: move mnt_idmap

2023-01-19T08:24:30Z

Now that we converted everything to just rely on struct mnt_idmap move it all into a separate file. This ensure that no code can poke around in struct mnt_idmap without any dedicated helpers and makes it easier to extend it in the future. Filesystems will now not be able to conflate mount and filesystem idmappings as they are two distinct types and require distinct helpers that cannot be used interchangeably. We are now also able to extend struct mnt_idmap as we see fit. Acked-by: Dave Chinner Reviewed-by: Christoph Hellwig Signed-off-by: Christian Brauner (Microsoft)

fs: port i_{g,u}id_into_vfs{g,u}id() to mnt_idmap

2023-01-19T08:24:29Z

Convert to struct mnt_idmap. Remove legacy file_mnt_user_ns() and mnt_user_ns(). Last cycle we merged the necessary infrastructure in 256c8aed2b42 ("fs: introduce dedicated idmap type for mounts"). This is just the conversion to struct mnt_idmap. Currently we still pass around the plain namespace that was attached to a mount. This is in general pretty convenient but it makes it easy to conflate namespaces that are relevant on the filesystem with namespaces that are relevent on the mount level. Especially for non-vfs developers without detailed knowledge in this area this can be a potential source for bugs. Once the conversion to struct mnt_idmap is done all helpers down to the really low-level helpers will take a struct mnt_idmap argument instead of two namespace arguments. This way it becomes impossible to conflate the two eliminating the possibility of any bugs. All of the vfs and all filesystems only operate on struct mnt_idmap. Acked-by: Dave Chinner Reviewed-by: Christoph Hellwig Signed-off-by: Christian Brauner (Microsoft)

Merge tag 'fs.idmapped.mnt_idmap.v6.2' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/idmapping

2022-12-13T03:30:18Z

Pull idmapping updates from Christian Brauner: "Last cycle we've already made the interaction with idmapped mounts more robust and type safe by introducing the vfs{g,u}id_t type. This cycle we concluded the conversion and removed the legacy helpers. Currently we still pass around the plain namespace that was attached to a mount. This is in general pretty convenient but it makes it easy to conflate namespaces that are relevant on the filesystem - with namespaces that are relevent on the mount level. Especially for filesystem developers without detailed knowledge in this area this can be a potential source for bugs. Instead of passing the plain namespace we introduce a dedicated type struct mnt_idmap and replace the pointer with a pointer to a struct mnt_idmap. There are no semantic or size changes for the mount struct caused by this. We then start converting all places aware of idmapped mounts to rely on struct mnt_idmap. Once the conversion is done all helpers down to the really low-level make_vfs{g,u}id() and from_vfs{g,u}id() will take a struct mnt_idmap argument instead of two namespace arguments. This way it becomes impossible to conflate the two removing and thus eliminating the possibility of any bugs. Fwiw, I fixed some issues in that area a while ago in ntfs3 and ksmbd in the past. Afterwards only low-level code can ultimately use the associated namespace for any permission checks. Even most of the vfs can be completely obivious about this ultimately and filesystems will never interact with it in any form in the future. A struct mnt_idmap currently encompasses a simple refcount and pointer to the relevant namespace the mount is idmapped to. If a mount isn't idmapped then it will point to a static nop_mnt_idmap and if it doesn't that it is idmapped. As usual there are no allocations or anything happening for non-idmapped mounts. Everthing is carefully written to be a nop for non-idmapped mounts as has always been the case. If an idmapped mount is created a struct mnt_idmap is allocated and a reference taken on the relevant namespace. Each mount that gets idmapped or inherits the idmap simply bumps the reference count on struct mnt_idmap. Just a reminder that we only allow a mount to change it's idmapping a single time and only if it hasn't already been attached to the filesystems and has no active writers. The actual changes are fairly straightforward but this will have huge benefits for maintenance and security in the long run even if it causes some churn. Note that this also makes it possible to extend struct mount_idmap in the future. For example, it would be possible to place the namespace pointer in an anonymous union together with an idmapping struct. This would allow us to expose an api to userspace that would let it specify idmappings directly instead of having to go through the detour of setting up namespaces at all" * tag 'fs.idmapped.mnt_idmap.v6.2' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/idmapping: acl: conver higher-level helpers to rely on mnt_idmap fs: introduce dedicated idmap type for mounts

copy_mnt_ns(): handle a corner case (overmounted mntns bindings) saner

2022-11-25T03:55:57Z

copy_mnt_ns() has the old tree copied, with mntns binding *and* anything bound on top of them skipped. Then it proceeds to walk both trees in parallel. Unfortunately, it doesn't get the "skip the stuff we'd skipped when copying" quite right. Consequences are minor (the ->mnt_root comparison will return the situation to sanity pretty soon and the worst we get is the unexpected subset of opened non-directories being switched to new namespace), but it's confusing enough and it's not hard to get the expected behaviour... Signed-off-by: Al Viro

fs: introduce dedicated idmap type for mounts

2022-10-31T16:47:42Z

Last cycle we've already made the interaction with idmapped mounts more robust and type safe by introducing the vfs{g,u}id_t type. This cycle we concluded the conversion and removed the legacy helpers. Currently we still pass around the plain namespace that was attached to a mount. This is in general pretty convenient but it makes it easy to conflate filesystem and mount namespaces and what different roles they have to play. Especially for filesystem developers without much experience in this area this is an easy source for bugs. Instead of passing the plain namespace we introduce a dedicated type struct mnt_idmap and replace the pointer with a pointer to a struct mnt_idmap. There are no semantic or size changes for the mount struct caused by this. We then start converting all places aware of idmapped mounts to rely on struct mnt_idmap. Once the conversion is done all helpers down to the really low-level make_vfs{g,u}id() and from_vfs{g,u}id() will take a struct mnt_idmap argument instead of two namespace arguments. This way it becomes impossible to conflate the two, removing and thus eliminating the possibility of any bugs. Fwiw, I fixed some issues in that area a while ago in ntfs3 and ksmbd in the past. Afterwards, only low-level code can ultimately use the associated namespace for any permission checks. Even most of the vfs can be ultimately completely oblivious about this and filesystems will never interact with it directly in any form in the future. A struct mnt_idmap currently encompasses a simple refcount and a pointer to the relevant namespace the mount is idmapped to. If a mount isn't idmapped then it will point to a static nop_mnt_idmap. If it is an idmapped mount it will point to a new struct mnt_idmap. As usual there are no allocations or anything happening for non-idmapped mounts. Everthing is carefully written to be a nop for non-idmapped mounts as has always been the case. If an idmapped mount or mount tree is created a new struct mnt_idmap is allocated and a reference taken on the relevant namespace. For each mount in a mount tree that gets idmapped or a mount that inherits the idmap when it is cloned the reference count on the associated struct mnt_idmap is bumped. Just a reminder that we only allow a mount to change it's idmapping a single time and only if it hasn't already been attached to the filesystems and has no active writers. The actual changes are fairly straightforward. This will have huge benefits for maintenance and security in the long run even if it causes some churn. I'm aware that there's some cost for all of you. And I'll commit to doing this work and make this as painless as I can. Note that this also makes it possible to extend struct mount_idmap in the future. For example, it would be possible to place the namespace pointer in an anonymous union together with an idmapping struct. This would allow us to expose an api to userspace that would let it specify idmappings directly instead of having to go through the detour of setting up namespaces at all. This just adds the infrastructure and doesn't do any conversions. Reviewed-by: Seth Forshee (DigitalOcean) Signed-off-by: Christian Brauner (Microsoft)

fs: require CAP_SYS_ADMIN in target namespace for idmapped mounts

2022-08-17T09:27:11Z

Idmapped mounts should not allow a user to map file ownsership into a range of ids which is not under the control of that user. However, we currently don't check whether the mounter is privileged wrt to the target user namespace. Currently no FS_USERNS_MOUNT filesystems support idmapped mounts, thus this is not a problem as only CAP_SYS_ADMIN in init_user_ns is allowed to set up idmapped mounts. But this could change in the future, so add a check to refuse to create idmapped mounts when the mounter does not have CAP_SYS_ADMIN in the target user namespace. Fixes: bd303368b776 ("fs: support mapped mounts of mapped filesystems") Signed-off-by: Seth Forshee Reviewed-by: Christian Brauner (Microsoft) Link: https://lore.kernel.org/r/20220816164752.2595240-1-sforshee@digitalocean.com Signed-off-by: Christian Brauner (Microsoft)

switch try_to_unlazy_next() to __legitimize_mnt()

2022-07-05T20:18:21Z

The tricky case (__legitimize_mnt() failing after having grabbed a reference) can be trivially dealt with by leaving nd->path.mnt non-NULL, for terminate_walk() to drop it. legitimize_mnt() becomes static after that. Signed-off-by: Al Viro