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Author SHA1 Message Date
Linus Torvalds
7d6beb71da idmapped-mounts-v5.12
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Merge tag 'idmapped-mounts-v5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux

Pull idmapped mounts from Christian Brauner:
 "This introduces idmapped mounts which has been in the making for some
  time. Simply put, different mounts can expose the same file or
  directory with different ownership. This initial implementation comes
  with ports for fat, ext4 and with Christoph's port for xfs with more
  filesystems being actively worked on by independent people and
  maintainers.

  Idmapping mounts handle a wide range of long standing use-cases. Here
  are just a few:

   - Idmapped mounts make it possible to easily share files between
     multiple users or multiple machines especially in complex
     scenarios. For example, idmapped mounts will be used in the
     implementation of portable home directories in
     systemd-homed.service(8) where they allow users to move their home
     directory to an external storage device and use it on multiple
     computers where they are assigned different uids and gids. This
     effectively makes it possible to assign random uids and gids at
     login time.

   - It is possible to share files from the host with unprivileged
     containers without having to change ownership permanently through
     chown(2).

   - It is possible to idmap a container's rootfs and without having to
     mangle every file. For example, Chromebooks use it to share the
     user's Download folder with their unprivileged containers in their
     Linux subsystem.

   - It is possible to share files between containers with
     non-overlapping idmappings.

   - Filesystem that lack a proper concept of ownership such as fat can
     use idmapped mounts to implement discretionary access (DAC)
     permission checking.

   - They allow users to efficiently changing ownership on a per-mount
     basis without having to (recursively) chown(2) all files. In
     contrast to chown (2) changing ownership of large sets of files is
     instantenous with idmapped mounts. This is especially useful when
     ownership of a whole root filesystem of a virtual machine or
     container is changed. With idmapped mounts a single syscall
     mount_setattr syscall will be sufficient to change the ownership of
     all files.

   - Idmapped mounts always take the current ownership into account as
     idmappings specify what a given uid or gid is supposed to be mapped
     to. This contrasts with the chown(2) syscall which cannot by itself
     take the current ownership of the files it changes into account. It
     simply changes the ownership to the specified uid and gid. This is
     especially problematic when recursively chown(2)ing a large set of
     files which is commong with the aforementioned portable home
     directory and container and vm scenario.

   - Idmapped mounts allow to change ownership locally, restricting it
     to specific mounts, and temporarily as the ownership changes only
     apply as long as the mount exists.

  Several userspace projects have either already put up patches and
  pull-requests for this feature or will do so should you decide to pull
  this:

   - systemd: In a wide variety of scenarios but especially right away
     in their implementation of portable home directories.

         https://systemd.io/HOME_DIRECTORY/

   - container runtimes: containerd, runC, LXD:To share data between
     host and unprivileged containers, unprivileged and privileged
     containers, etc. The pull request for idmapped mounts support in
     containerd, the default Kubernetes runtime is already up for quite
     a while now: https://github.com/containerd/containerd/pull/4734

   - The virtio-fs developers and several users have expressed interest
     in using this feature with virtual machines once virtio-fs is
     ported.

   - ChromeOS: Sharing host-directories with unprivileged containers.

  I've tightly synced with all those projects and all of those listed
  here have also expressed their need/desire for this feature on the
  mailing list. For more info on how people use this there's a bunch of
  talks about this too. Here's just two recent ones:

      https://www.cncf.io/wp-content/uploads/2020/12/Rootless-Containers-in-Gitpod.pdf
      https://fosdem.org/2021/schedule/event/containers_idmap/

  This comes with an extensive xfstests suite covering both ext4 and
  xfs:

      https://git.kernel.org/brauner/xfstests-dev/h/idmapped_mounts

  It covers truncation, creation, opening, xattrs, vfscaps, setid
  execution, setgid inheritance and more both with idmapped and
  non-idmapped mounts. It already helped to discover an unrelated xfs
  setgid inheritance bug which has since been fixed in mainline. It will
  be sent for inclusion with the xfstests project should you decide to
  merge this.

  In order to support per-mount idmappings vfsmounts are marked with
  user namespaces. The idmapping of the user namespace will be used to
  map the ids of vfs objects when they are accessed through that mount.
  By default all vfsmounts are marked with the initial user namespace.
  The initial user namespace is used to indicate that a mount is not
  idmapped. All operations behave as before and this is verified in the
  testsuite.

  Based on prior discussions we want to attach the whole user namespace
  and not just a dedicated idmapping struct. This allows us to reuse all
  the helpers that already exist for dealing with idmappings instead of
  introducing a whole new range of helpers. In addition, if we decide in
  the future that we are confident enough to enable unprivileged users
  to setup idmapped mounts the permission checking can take into account
  whether the caller is privileged in the user namespace the mount is
  currently marked with.

  The user namespace the mount will be marked with can be specified by
  passing a file descriptor refering to the user namespace as an
  argument to the new mount_setattr() syscall together with the new
  MOUNT_ATTR_IDMAP flag. The system call follows the openat2() pattern
  of extensibility.

  The following conditions must be met in order to create an idmapped
  mount:

   - The caller must currently have the CAP_SYS_ADMIN capability in the
     user namespace the underlying filesystem has been mounted in.

   - The underlying filesystem must support idmapped mounts.

   - The mount must not already be idmapped. This also implies that the
     idmapping of a mount cannot be altered once it has been idmapped.

   - The mount must be a detached/anonymous mount, i.e. it must have
     been created by calling open_tree() with the OPEN_TREE_CLONE flag
     and it must not already have been visible in the filesystem.

  The last two points guarantee easier semantics for userspace and the
  kernel and make the implementation significantly simpler.

  By default vfsmounts are marked with the initial user namespace and no
  behavioral or performance changes are observed.

  The manpage with a detailed description can be found here:

      1d7b902e28

  In order to support idmapped mounts, filesystems need to be changed
  and mark themselves with the FS_ALLOW_IDMAP flag in fs_flags. The
  patches to convert individual filesystem are not very large or
  complicated overall as can be seen from the included fat, ext4, and
  xfs ports. Patches for other filesystems are actively worked on and
  will be sent out separately. The xfstestsuite can be used to verify
  that port has been done correctly.

  The mount_setattr() syscall is motivated independent of the idmapped
  mounts patches and it's been around since July 2019. One of the most
  valuable features of the new mount api is the ability to perform
  mounts based on file descriptors only.

  Together with the lookup restrictions available in the openat2()
  RESOLVE_* flag namespace which we added in v5.6 this is the first time
  we are close to hardened and race-free (e.g. symlinks) mounting and
  path resolution.

  While userspace has started porting to the new mount api to mount
  proper filesystems and create new bind-mounts it is currently not
  possible to change mount options of an already existing bind mount in
  the new mount api since the mount_setattr() syscall is missing.

  With the addition of the mount_setattr() syscall we remove this last
  restriction and userspace can now fully port to the new mount api,
  covering every use-case the old mount api could. We also add the
  crucial ability to recursively change mount options for a whole mount
  tree, both removing and adding mount options at the same time. This
  syscall has been requested multiple times by various people and
  projects.

  There is a simple tool available at

      https://github.com/brauner/mount-idmapped

  that allows to create idmapped mounts so people can play with this
  patch series. I'll add support for the regular mount binary should you
  decide to pull this in the following weeks:

  Here's an example to a simple idmapped mount of another user's home
  directory:

	u1001@f2-vm:/$ sudo ./mount --idmap both:1000:1001:1 /home/ubuntu/ /mnt

	u1001@f2-vm:/$ ls -al /home/ubuntu/
	total 28
	drwxr-xr-x 2 ubuntu ubuntu 4096 Oct 28 22:07 .
	drwxr-xr-x 4 root   root   4096 Oct 28 04:00 ..
	-rw------- 1 ubuntu ubuntu 3154 Oct 28 22:12 .bash_history
	-rw-r--r-- 1 ubuntu ubuntu  220 Feb 25  2020 .bash_logout
	-rw-r--r-- 1 ubuntu ubuntu 3771 Feb 25  2020 .bashrc
	-rw-r--r-- 1 ubuntu ubuntu  807 Feb 25  2020 .profile
	-rw-r--r-- 1 ubuntu ubuntu    0 Oct 16 16:11 .sudo_as_admin_successful
	-rw------- 1 ubuntu ubuntu 1144 Oct 28 00:43 .viminfo

	u1001@f2-vm:/$ ls -al /mnt/
	total 28
	drwxr-xr-x  2 u1001 u1001 4096 Oct 28 22:07 .
	drwxr-xr-x 29 root  root  4096 Oct 28 22:01 ..
	-rw-------  1 u1001 u1001 3154 Oct 28 22:12 .bash_history
	-rw-r--r--  1 u1001 u1001  220 Feb 25  2020 .bash_logout
	-rw-r--r--  1 u1001 u1001 3771 Feb 25  2020 .bashrc
	-rw-r--r--  1 u1001 u1001  807 Feb 25  2020 .profile
	-rw-r--r--  1 u1001 u1001    0 Oct 16 16:11 .sudo_as_admin_successful
	-rw-------  1 u1001 u1001 1144 Oct 28 00:43 .viminfo

	u1001@f2-vm:/$ touch /mnt/my-file

	u1001@f2-vm:/$ setfacl -m u:1001:rwx /mnt/my-file

	u1001@f2-vm:/$ sudo setcap -n 1001 cap_net_raw+ep /mnt/my-file

	u1001@f2-vm:/$ ls -al /mnt/my-file
	-rw-rwxr--+ 1 u1001 u1001 0 Oct 28 22:14 /mnt/my-file

	u1001@f2-vm:/$ ls -al /home/ubuntu/my-file
	-rw-rwxr--+ 1 ubuntu ubuntu 0 Oct 28 22:14 /home/ubuntu/my-file

	u1001@f2-vm:/$ getfacl /mnt/my-file
	getfacl: Removing leading '/' from absolute path names
	# file: mnt/my-file
	# owner: u1001
	# group: u1001
	user::rw-
	user:u1001:rwx
	group::rw-
	mask::rwx
	other::r--

	u1001@f2-vm:/$ getfacl /home/ubuntu/my-file
	getfacl: Removing leading '/' from absolute path names
	# file: home/ubuntu/my-file
	# owner: ubuntu
	# group: ubuntu
	user::rw-
	user:ubuntu:rwx
	group::rw-
	mask::rwx
	other::r--"

* tag 'idmapped-mounts-v5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux: (41 commits)
  xfs: remove the possibly unused mp variable in xfs_file_compat_ioctl
  xfs: support idmapped mounts
  ext4: support idmapped mounts
  fat: handle idmapped mounts
  tests: add mount_setattr() selftests
  fs: introduce MOUNT_ATTR_IDMAP
  fs: add mount_setattr()
  fs: add attr_flags_to_mnt_flags helper
  fs: split out functions to hold writers
  namespace: only take read lock in do_reconfigure_mnt()
  mount: make {lock,unlock}_mount_hash() static
  namespace: take lock_mount_hash() directly when changing flags
  nfs: do not export idmapped mounts
  overlayfs: do not mount on top of idmapped mounts
  ecryptfs: do not mount on top of idmapped mounts
  ima: handle idmapped mounts
  apparmor: handle idmapped mounts
  fs: make helpers idmap mount aware
  exec: handle idmapped mounts
  would_dump: handle idmapped mounts
  ...
2021-02-23 13:39:45 -08:00
Sargun Dhillon
335d3fc579 ovl: implement volatile-specific fsync error behaviour
Overlayfs's volatile option allows the user to bypass all forced sync calls
to the upperdir filesystem. This comes at the cost of safety. We can never
ensure that the user's data is intact, but we can make a best effort to
expose whether or not the data is likely to be in a bad state.

The best way to handle this in the time being is that if an overlayfs's
upperdir experiences an error after a volatile mount occurs, that error
will be returned on fsync, fdatasync, sync, and syncfs. This is
contradictory to the traditional behaviour of VFS which fails the call
once, and only raises an error if a subsequent fsync error has occurred,
and been raised by the filesystem.

One awkward aspect of the patch is that we have to manually set the
superblock's errseq_t after the sync_fs callback as opposed to just
returning an error from syncfs. This is because the call chain looks
something like this:

sys_syncfs ->
	sync_filesystem ->
		__sync_filesystem ->
			/* The return value is ignored here
			sb->s_op->sync_fs(sb)
			_sync_blockdev
		/* Where the VFS fetches the error to raise to userspace */
		errseq_check_and_advance

Because of this we call errseq_set every time the sync_fs callback occurs.
Due to the nature of this seen / unseen dichotomy, if the upperdir is an
inconsistent state at the initial mount time, overlayfs will refuse to
mount, as overlayfs cannot get a snapshot of the upperdir's errseq that
will increment on error until the user calls syncfs.

Signed-off-by: Sargun Dhillon <sargun@sargun.me>
Suggested-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Fixes: c86243b090 ("ovl: provide a mount option "volatile"")
Cc: stable@vger.kernel.org
Reviewed-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2021-01-28 10:22:48 +01:00
Amir Goldstein
03fedf9359 ovl: skip getxattr of security labels
When inode has no listxattr op of its own (e.g. squashfs) vfs_listxattr
calls the LSM inode_listsecurity hooks to list the xattrs that LSMs will
intercept in inode_getxattr hooks.

When selinux LSM is installed but not initialized, it will list the
security.selinux xattr in inode_listsecurity, but will not intercept it
in inode_getxattr.  This results in -ENODATA for a getxattr call for an
xattr returned by listxattr.

This situation was manifested as overlayfs failure to copy up lower
files from squashfs when selinux is built-in but not initialized,
because ovl_copy_xattr() iterates the lower inode xattrs by
vfs_listxattr() and vfs_getxattr().

ovl_copy_xattr() skips copy up of security labels that are indentified by
inode_copy_up_xattr LSM hooks, but it does that after vfs_getxattr().
Since we are not going to copy them, skip vfs_getxattr() of the security
labels.

Reported-by: Michael Labriola <michael.d.labriola@gmail.com>
Tested-by: Michael Labriola <michael.d.labriola@gmail.com>
Link: https://lore.kernel.org/linux-unionfs/2nv9d47zt7.fsf@aldarion.sourceruckus.org/
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2021-01-28 10:22:48 +01:00
Liangyan
e04527fefb ovl: fix dentry leak in ovl_get_redirect
We need to lock d_parent->d_lock before dget_dlock, or this may
have d_lockref updated parallelly like calltrace below which will
cause dentry->d_lockref leak and risk a crash.

     CPU 0                                CPU 1
ovl_set_redirect                       lookup_fast
  ovl_get_redirect                       __d_lookup
    dget_dlock
      //no lock protection here            spin_lock(&dentry->d_lock)
      dentry->d_lockref.count++            dentry->d_lockref.count++

[   49.799059] PGD 800000061fed7067 P4D 800000061fed7067 PUD 61fec5067 PMD 0
[   49.799689] Oops: 0002 [#1] SMP PTI
[   49.800019] CPU: 2 PID: 2332 Comm: node Not tainted 4.19.24-7.20.al7.x86_64 #1
[   49.800678] Hardware name: Alibaba Cloud Alibaba Cloud ECS, BIOS 8a46cfe 04/01/2014
[   49.801380] RIP: 0010:_raw_spin_lock+0xc/0x20
[   49.803470] RSP: 0018:ffffac6fc5417e98 EFLAGS: 00010246
[   49.803949] RAX: 0000000000000000 RBX: ffff93b8da3446c0 RCX: 0000000a00000000
[   49.804600] RDX: 0000000000000001 RSI: 000000000000000a RDI: 0000000000000088
[   49.805252] RBP: 0000000000000000 R08: 0000000000000000 R09: ffffffff993cf040
[   49.805898] R10: ffff93b92292e580 R11: ffffd27f188a4b80 R12: 0000000000000000
[   49.806548] R13: 00000000ffffff9c R14: 00000000fffffffe R15: ffff93b8da3446c0
[   49.807200] FS:  00007ffbedffb700(0000) GS:ffff93b927880000(0000) knlGS:0000000000000000
[   49.807935] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   49.808461] CR2: 0000000000000088 CR3: 00000005e3f74006 CR4: 00000000003606a0
[   49.809113] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[   49.809758] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[   49.810410] Call Trace:
[   49.810653]  d_delete+0x2c/0xb0
[   49.810951]  vfs_rmdir+0xfd/0x120
[   49.811264]  do_rmdir+0x14f/0x1a0
[   49.811573]  do_syscall_64+0x5b/0x190
[   49.811917]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
[   49.812385] RIP: 0033:0x7ffbf505ffd7
[   49.814404] RSP: 002b:00007ffbedffada8 EFLAGS: 00000297 ORIG_RAX: 0000000000000054
[   49.815098] RAX: ffffffffffffffda RBX: 00007ffbedffb640 RCX: 00007ffbf505ffd7
[   49.815744] RDX: 0000000004449700 RSI: 0000000000000000 RDI: 0000000006c8cd50
[   49.816394] RBP: 00007ffbedffaea0 R08: 0000000000000000 R09: 0000000000017d0b
[   49.817038] R10: 0000000000000000 R11: 0000000000000297 R12: 0000000000000012
[   49.817687] R13: 00000000072823d8 R14: 00007ffbedffb700 R15: 00000000072823d8
[   49.818338] Modules linked in: pvpanic cirrusfb button qemu_fw_cfg atkbd libps2 i8042
[   49.819052] CR2: 0000000000000088
[   49.819368] ---[ end trace 4e652b8aa299aa2d ]---
[   49.819796] RIP: 0010:_raw_spin_lock+0xc/0x20
[   49.821880] RSP: 0018:ffffac6fc5417e98 EFLAGS: 00010246
[   49.822363] RAX: 0000000000000000 RBX: ffff93b8da3446c0 RCX: 0000000a00000000
[   49.823008] RDX: 0000000000000001 RSI: 000000000000000a RDI: 0000000000000088
[   49.823658] RBP: 0000000000000000 R08: 0000000000000000 R09: ffffffff993cf040
[   49.825404] R10: ffff93b92292e580 R11: ffffd27f188a4b80 R12: 0000000000000000
[   49.827147] R13: 00000000ffffff9c R14: 00000000fffffffe R15: ffff93b8da3446c0
[   49.828890] FS:  00007ffbedffb700(0000) GS:ffff93b927880000(0000) knlGS:0000000000000000
[   49.830725] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   49.832359] CR2: 0000000000000088 CR3: 00000005e3f74006 CR4: 00000000003606a0
[   49.834085] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[   49.835792] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

Cc: <stable@vger.kernel.org>
Fixes: a6c6065511 ("ovl: redirect on rename-dir")
Signed-off-by: Liangyan <liangyan.peng@linux.alibaba.com>
Reviewed-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2021-01-28 10:22:48 +01:00
Miklos Szeredi
b854cc659d ovl: avoid deadlock on directory ioctl
The function ovl_dir_real_file() currently uses the inode lock to serialize
writes to the od->upperfile field.

However, this function will get called by ovl_ioctl_set_flags(), which
utilizes the inode lock too.  In this case ovl_dir_real_file() will try to
claim a lock that is owned by a function in its call stack, which won't get
released before ovl_dir_real_file() returns.

Fix by replacing the open coded compare and exchange by an explicit atomic
op.

Fixes: 61536bed21 ("ovl: support [S|G]ETFLAGS and FS[S|G]ETXATTR ioctls for directories")
Cc: stable@vger.kernel.org # v5.10
Reported-by: Icenowy Zheng <icenowy@aosc.io>
Tested-by: Icenowy Zheng <icenowy@aosc.io>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2021-01-28 10:22:48 +01:00
Miklos Szeredi
554677b972 ovl: perform vfs_getxattr() with mounter creds
The vfs_getxattr() in ovl_xattr_set() is used to check whether an xattr
exist on a lower layer file that is to be removed.  If the xattr does not
exist, then no need to copy up the file.

This call of vfs_getxattr() wasn't wrapped in credential override, and this
is probably okay.  But for consitency wrap this instance as well.

Reported-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2021-01-28 10:22:48 +01:00
Miklos Szeredi
9efb069de4 ovl: add warning on user_ns mismatch
Currently there's no way to create an overlay filesystem outside of the
current user namespace.  Make sure that if this assumption changes it
doesn't go unnoticed.

Reported-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2021-01-28 10:22:48 +01:00
Christian Brauner
029a52ada6
overlayfs: do not mount on top of idmapped mounts
Prevent overlayfs from being mounted on top of idmapped mounts.
Stacking filesystems need to be prevented from being mounted on top of
idmapped mounts until they have have been converted to handle this.

Link: https://lore.kernel.org/r/20210121131959.646623-29-christian.brauner@ubuntu.com
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: James Morris <jamorris@linux.microsoft.com>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
2021-01-24 14:27:20 +01:00
Christian Brauner
549c729771
fs: make helpers idmap mount aware
Extend some inode methods with an additional user namespace argument. A
filesystem that is aware of idmapped mounts will receive the user
namespace the mount has been marked with. This can be used for
additional permission checking and also to enable filesystems to
translate between uids and gids if they need to. We have implemented all
relevant helpers in earlier patches.

As requested we simply extend the exisiting inode method instead of
introducing new ones. This is a little more code churn but it's mostly
mechanical and doesnt't leave us with additional inode methods.

Link: https://lore.kernel.org/r/20210121131959.646623-25-christian.brauner@ubuntu.com
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
2021-01-24 14:27:20 +01:00
Christian Brauner
6521f89170
namei: prepare for idmapped mounts
The various vfs_*() helpers are called by filesystems or by the vfs
itself to perform core operations such as create, link, mkdir, mknod, rename,
rmdir, tmpfile and unlink. Enable them to handle idmapped mounts. If the
inode is accessed through an idmapped mount map it into the
mount's user namespace and pass it down. Afterwards the checks and
operations are identical to non-idmapped mounts. If the initial user
namespace is passed nothing changes so non-idmapped mounts will see
identical behavior as before.

Link: https://lore.kernel.org/r/20210121131959.646623-15-christian.brauner@ubuntu.com
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
2021-01-24 14:27:18 +01:00
Christian Brauner
9fe6145097
namei: introduce struct renamedata
In order to handle idmapped mounts we will extend the vfs rename helper
to take two new arguments in follow up patches. Since this operations
already takes a bunch of arguments add a simple struct renamedata and
make the current helper use it before we extend it.

Link: https://lore.kernel.org/r/20210121131959.646623-14-christian.brauner@ubuntu.com
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
2021-01-24 14:27:18 +01:00
Tycho Andersen
c7c7a1a18a
xattr: handle idmapped mounts
When interacting with extended attributes the vfs verifies that the
caller is privileged over the inode with which the extended attribute is
associated. For posix access and posix default extended attributes a uid
or gid can be stored on-disk. Let the functions handle posix extended
attributes on idmapped mounts. If the inode is accessed through an
idmapped mount we need to map it according to the mount's user
namespace. Afterwards the checks are identical to non-idmapped mounts.
This has no effect for e.g. security xattrs since they don't store uids
or gids and don't perform permission checks on them like posix acls do.

Link: https://lore.kernel.org/r/20210121131959.646623-10-christian.brauner@ubuntu.com
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: James Morris <jamorris@linux.microsoft.com>
Signed-off-by: Tycho Andersen <tycho@tycho.pizza>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
2021-01-24 14:27:17 +01:00
Christian Brauner
e65ce2a50c
acl: handle idmapped mounts
The posix acl permission checking helpers determine whether a caller is
privileged over an inode according to the acls associated with the
inode. Add helpers that make it possible to handle acls on idmapped
mounts.

The vfs and the filesystems targeted by this first iteration make use of
posix_acl_fix_xattr_from_user() and posix_acl_fix_xattr_to_user() to
translate basic posix access and default permissions such as the
ACL_USER and ACL_GROUP type according to the initial user namespace (or
the superblock's user namespace) to and from the caller's current user
namespace. Adapt these two helpers to handle idmapped mounts whereby we
either map from or into the mount's user namespace depending on in which
direction we're translating.
Similarly, cap_convert_nscap() is used by the vfs to translate user
namespace and non-user namespace aware filesystem capabilities from the
superblock's user namespace to the caller's user namespace. Enable it to
handle idmapped mounts by accounting for the mount's user namespace.

In addition the fileystems targeted in the first iteration of this patch
series make use of the posix_acl_chmod() and, posix_acl_update_mode()
helpers. Both helpers perform permission checks on the target inode. Let
them handle idmapped mounts. These two helpers are called when posix
acls are set by the respective filesystems to handle this case we extend
the ->set() method to take an additional user namespace argument to pass
the mount's user namespace down.

Link: https://lore.kernel.org/r/20210121131959.646623-9-christian.brauner@ubuntu.com
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
2021-01-24 14:27:17 +01:00
Christian Brauner
2f221d6f7b
attr: handle idmapped mounts
When file attributes are changed most filesystems rely on the
setattr_prepare(), setattr_copy(), and notify_change() helpers for
initialization and permission checking. Let them handle idmapped mounts.
If the inode is accessed through an idmapped mount map it into the
mount's user namespace. Afterwards the checks are identical to
non-idmapped mounts. If the initial user namespace is passed nothing
changes so non-idmapped mounts will see identical behavior as before.

Helpers that perform checks on the ia_uid and ia_gid fields in struct
iattr assume that ia_uid and ia_gid are intended values and have already
been mapped correctly at the userspace-kernelspace boundary as we
already do today. If the initial user namespace is passed nothing
changes so non-idmapped mounts will see identical behavior as before.

Link: https://lore.kernel.org/r/20210121131959.646623-8-christian.brauner@ubuntu.com
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
2021-01-24 14:27:16 +01:00
Christian Brauner
21cb47be6f
inode: make init and permission helpers idmapped mount aware
The inode_owner_or_capable() helper determines whether the caller is the
owner of the inode or is capable with respect to that inode. Allow it to
handle idmapped mounts. If the inode is accessed through an idmapped
mount it according to the mount's user namespace. Afterwards the checks
are identical to non-idmapped mounts. If the initial user namespace is
passed nothing changes so non-idmapped mounts will see identical
behavior as before.

Similarly, allow the inode_init_owner() helper to handle idmapped
mounts. It initializes a new inode on idmapped mounts by mapping the
fsuid and fsgid of the caller from the mount's user namespace. If the
initial user namespace is passed nothing changes so non-idmapped mounts
will see identical behavior as before.

Link: https://lore.kernel.org/r/20210121131959.646623-7-christian.brauner@ubuntu.com
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: James Morris <jamorris@linux.microsoft.com>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
2021-01-24 14:27:16 +01:00
Christian Brauner
47291baa8d
namei: make permission helpers idmapped mount aware
The two helpers inode_permission() and generic_permission() are used by
the vfs to perform basic permission checking by verifying that the
caller is privileged over an inode. In order to handle idmapped mounts
we extend the two helpers with an additional user namespace argument.
On idmapped mounts the two helpers will make sure to map the inode
according to the mount's user namespace and then peform identical
permission checks to inode_permission() and generic_permission(). If the
initial user namespace is passed nothing changes so non-idmapped mounts
will see identical behavior as before.

Link: https://lore.kernel.org/r/20210121131959.646623-6-christian.brauner@ubuntu.com
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: James Morris <jamorris@linux.microsoft.com>
Acked-by: Serge Hallyn <serge@hallyn.com>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
2021-01-24 14:27:16 +01:00
Christian Brauner
0558c1bf5a
capability: handle idmapped mounts
In order to determine whether a caller holds privilege over a given
inode the capability framework exposes the two helpers
privileged_wrt_inode_uidgid() and capable_wrt_inode_uidgid(). The former
verifies that the inode has a mapping in the caller's user namespace and
the latter additionally verifies that the caller has the requested
capability in their current user namespace.
If the inode is accessed through an idmapped mount map it into the
mount's user namespace. Afterwards the checks are identical to
non-idmapped inodes. If the initial user namespace is passed all
operations are a nop so non-idmapped mounts will not see a change in
behavior.

Link: https://lore.kernel.org/r/20210121131959.646623-5-christian.brauner@ubuntu.com
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: James Morris <jamorris@linux.microsoft.com>
Acked-by: Serge Hallyn <serge@hallyn.com>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
2021-01-24 14:27:16 +01:00
Miklos Szeredi
459c7c565a ovl: unprivieged mounts
Enable unprivileged user namespace mounts of overlayfs.  Overlayfs's
permission model (*) ensures that the mounter itself cannot gain additional
privileges by the act of creating an overlayfs mount.

This feature request is coming from the "rootless" container crowd.

(*) Documentation/filesystems/overlayfs.txt#Permission model

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-12-14 15:26:14 +01:00
Miklos Szeredi
87b2c60c61 ovl: do not get metacopy for userxattr
When looking up an inode on the lower layer for which the mounter lacks
read permisison the metacopy check will fail.  This causes the lookup to
fail as well, even though the directory is readable.

So ignore EACCES for the "userxattr" case and assume no metacopy for the
unreadable file.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-12-14 15:26:14 +01:00
Miklos Szeredi
b6650dab40 ovl: do not fail because of O_NOATIME
In case the file cannot be opened with O_NOATIME because of lack of
capabilities, then clear O_NOATIME instead of failing.

Remove WARN_ON(), since it would now trigger if O_NOATIME was cleared.
Noticed by Amir Goldstein.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-12-14 15:26:14 +01:00
Miklos Szeredi
6939f977c5 ovl: do not fail when setting origin xattr
Comment above call already says this, but only EOPNOTSUPP is ignored, other
failures are not.

For example setting "user.*" will fail with EPERM on symlink/special.

Ignore this error as well.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-12-14 15:26:14 +01:00
Miklos Szeredi
2d2f2d7322 ovl: user xattr
Optionally allow using "user.overlay." namespace instead of
"trusted.overlay."

This is necessary for overlayfs to be able to be mounted in an unprivileged
namepsace.

Make the option explicit, since it makes the filesystem format be
incompatible.

Disable redirect_dir and metacopy options, because these would allow
privilege escalation through direct manipulation of the
"user.overlay.redirect" or "user.overlay.metacopy" xattrs.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
2020-12-14 15:26:14 +01:00
Miklos Szeredi
82a763e61e ovl: simplify file splice
generic_file_splice_read() and iter_file_splice_write() will call back into
f_op->iter_read() and f_op->iter_write() respectively.  These already do
the real file lookup and cred override.  So the code in ovl_splice_read()
and ovl_splice_write() is redundant.

In addition the ovl_file_accessed() call in ovl_splice_write() is
incorrect, though probably harmless.

Fix by calling generic_file_splice_read() and iter_file_splice_write()
directly.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-12-14 15:26:14 +01:00
Miklos Szeredi
89bdfaf93d ovl: make ioctl() safe
ovl_ioctl_set_flags() does a capability check using flags, but then the
real ioctl double-fetches flags and uses potentially different value.

The "Check the capability before cred override" comment misleading: user
can skip this check by presenting benign flags first and then overwriting
them to non-benign flags.

Just remove the cred override for now, hoping this doesn't cause a
regression.

The proper solution is to create a new setxflags i_op (patches are in the
works).

Xfstests don't show a regression.

Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Fixes: dab5ca8fd9 ("ovl: add lsattr/chattr support")
Cc: <stable@vger.kernel.org> # v4.19
2020-12-14 15:26:14 +01:00
Miklos Szeredi
c846af050f ovl: check privs before decoding file handle
CAP_DAC_READ_SEARCH is required by open_by_handle_at(2) so check it in
ovl_decode_real_fh() as well to prevent privilege escalation for
unprivileged overlay mounts.

[Amir] If the mounter is not capable in init ns, ovl_check_origin() and
ovl_verify_index() will not function as expected and this will break index
and nfs export features.  So check capability in ovl_can_decode_fh(), to
auto disable those features.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-12-14 15:26:14 +01:00
Chengguang Xu
c11faf3259 ovl: fix incorrect extent info in metacopy case
In metacopy case, we should use ovl_inode_realdata() instead of
ovl_inode_real() to get real inode which has data, so that
we can get correct information of extentes in ->fiemap operation.

Signed-off-by: Chengguang Xu <cgxu519@mykernel.net>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-11-12 11:31:56 +01:00
Miklos Szeredi
cef4cbff06 ovl: expand warning in ovl_d_real()
There was a syzbot report with this warning but insufficient information...

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-11-12 11:31:55 +01:00
Kevin Locke
0a8d0b64dd ovl: warn about orphan metacopy
When the lower file of a metacopy is inaccessible, -EIO is returned.  For
users not familiar with overlayfs internals, such as myself, the meaning of
this error may not be apparent or easy to determine, since the (metacopy)
file is present and open/stat succeed when accessed outside of the overlay.

Add a rate-limited warning for orphan metacopy to give users a hint when
investigating such errors.

Link: https://lore.kernel.org/linux-unionfs/CAOQ4uxi23Zsmfb4rCed1n=On0NNA5KZD74jjjeyz+et32sk-gg@mail.gmail.com/
Signed-off-by: Kevin Locke <kevin@kevinlocke.name>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-11-12 11:31:55 +01:00
Pavel Tikhomirov
5830fb6b54 ovl: introduce new "uuid=off" option for inodes index feature
This replaces uuid with null in overlayfs file handles and thus relaxes
uuid checks for overlay index feature. It is only possible in case there is
only one filesystem for all the work/upper/lower directories and bare file
handles from this backing filesystem are unique. In other case when we have
multiple filesystems lets just fallback to "uuid=on" which is and
equivalent of how it worked before with all uuid checks.

This is needed when overlayfs is/was mounted in a container with index
enabled (e.g.: to be able to resolve inotify watch file handles on it to
paths in CRIU), and this container is copied and started alongside with the
original one. This way the "copy" container can't have the same uuid on the
superblock and mounting the overlayfs from it later would fail.

That is an example of the problem on top of loop+ext4:

dd if=/dev/zero of=loopbackfile.img bs=100M count=10
losetup -fP loopbackfile.img
losetup -a
  #/dev/loop0: [64768]:35 (/loop-test/loopbackfile.img)
mkfs.ext4 loopbackfile.img
mkdir loop-mp
mount -o loop /dev/loop0 loop-mp
mkdir loop-mp/{lower,upper,work,merged}
mount -t overlay overlay -oindex=on,lowerdir=loop-mp/lower,\
upperdir=loop-mp/upper,workdir=loop-mp/work loop-mp/merged
umount loop-mp/merged
umount loop-mp
e2fsck -f /dev/loop0
tune2fs -U random /dev/loop0

mount -o loop /dev/loop0 loop-mp
mount -t overlay overlay -oindex=on,lowerdir=loop-mp/lower,\
upperdir=loop-mp/upper,workdir=loop-mp/work loop-mp/merged
  #mount: /loop-test/loop-mp/merged:
  #mount(2) system call failed: Stale file handle.

If you just change the uuid of the backing filesystem, overlay is not
mounting any more. In Virtuozzo we copy container disks (ploops) when
create the copy of container and we require fs uuid to be unique for a new
container.

Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-11-12 11:31:55 +01:00
Pavel Tikhomirov
1cdb0cb662 ovl: propagate ovl_fs to ovl_decode_real_fh and ovl_encode_real_fh
This will be used in next patch to be able to change uuid checks and add
uuid nullification based on ofs->config.index for a new "uuid=off" mode.

Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-11-12 11:31:55 +01:00
Amir Goldstein
be4df0cea0 ovl: use generic vfs_ioc_setflags_prepare() helper
Canonalize to ioctl FS_* flags instead of inode S_* flags.

Note that we do not call the helper vfs_ioc_fssetxattr_check()
for FS_IOC_FSSETXATTR ioctl. The reason is that underlying filesystem
will perform all the checks. We only need to perform the capability
check before overriding credentials.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Xiao Yang <yangx.jy@cn.fujitsu.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-10-06 15:38:15 +02:00
Amir Goldstein
61536bed21 ovl: support [S|G]ETFLAGS and FS[S|G]ETXATTR ioctls for directories
[S|G]ETFLAGS and FS[S|G]ETXATTR ioctls are applicable to both files and
directories, so add ioctl operations to dir as well.

We teach ovl_real_fdget() to get the realfile of directories which use
a different type of file->private_data.

Ifdef away compat ioctl implementation to conform to standard practice.

With this change, xfstest generic/079 which tests these ioctls on files
and directories passes.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Xiao Yang <yangx.jy@cn.fujitsu.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-10-06 15:38:14 +02:00
Miklos Szeredi
8f6ee74c27 ovl: rearrange ovl_can_list()
ovl_can_list() should return false for overlay private xattrs.  Since
currently these use the "trusted.overlay." prefix, they will always match
the "trusted." prefix as well, hence the test for being non-trusted will
not trigger.

Prepare for using the "user.overlay." namespace by moving the test for
private xattr before the test for non-trusted.

This patch doesn't change behavior.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-09-02 10:58:49 +02:00
Miklos Szeredi
43d193f844 ovl: enumerate private xattrs
Instead of passing the xattr name down to the ovl_do_*xattr() accessor
functions, pass an enumerated value.  The enum can use the same names as
the the previous #define for each xattr name.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-09-02 10:58:49 +02:00
Miklos Szeredi
610afc0bd4 ovl: pass ovl_fs down to functions accessing private xattrs
This paves the way for optionally using the "user.overlay." xattr
namespace.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-09-02 10:58:49 +02:00
Miklos Szeredi
26150ab5ea ovl: drop flags argument from ovl_do_setxattr()
All callers pass zero flags to ovl_do_setxattr().  So drop this argument.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-09-02 10:58:48 +02:00
Miklos Szeredi
7109704705 ovl: adhere to the vfs_ vs. ovl_do_ conventions for xattrs
Call ovl_do_*xattr() when accessing an overlay private xattr, vfs_*xattr()
otherwise.

This has an effect on debug output, which is made more consistent by this
patch.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-09-02 10:58:48 +02:00
Miklos Szeredi
d5dc7486e8 ovl: use ovl_do_getxattr() for private xattr
Use the convention of calling ovl_do_foo() for operations which are overlay
specific.

This patch is a no-op, and will have significance for supporting
"user.overlay." xattr namespace.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-09-02 10:58:48 +02:00
Miklos Szeredi
92f0d6c9cf ovl: fold ovl_getxattr() into ovl_get_redirect_xattr()
This is a partial revert (with some cleanups) of commit 993a0b2aec ("ovl:
Do not lose security.capability xattr over metadata file copy-up"), which
introduced ovl_getxattr() in the first place.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-09-02 10:58:48 +02:00
Miklos Szeredi
de7a52c9c6 ovl: clean up ovl_getxattr() in copy_up.c
Lose the padding and the failure message (in line with other parts of the
copy up process).  Return zero for both nonexistent or empty xattr.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-09-02 10:58:48 +02:00
Miklos Szeredi
fee0f2980a duplicate ovl_getxattr()
ovl_getattr() returns the value of an xattr in a kmalloced buffer.  There
are two callers:

 ovl_copy_up_meta_inode_data()	(copy_up.c)
 ovl_get_redirect_xattr()	(util.c)

This patch just copies ovl_getxattr() to copy_up.c, the following patches
will deal with the differences in idividual callers.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-09-02 10:58:48 +02:00
Vivek Goyal
c86243b090 ovl: provide a mount option "volatile"
Container folks are complaining that dnf/yum issues too many sync while
installing packages and this slows down the image build. Build requirement
is such that they don't care if a node goes down while build was still
going on. In that case, they will simply throw away unfinished layer and
start new build. So they don't care about syncing intermediate state to the
disk and hence don't want to pay the price associated with sync.

So they are asking for mount options where they can disable sync on overlay
mount point.

They primarily seem to have two use cases.

- For building images, they will mount overlay with nosync and then sync
  upper layer after unmounting overlay and reuse upper as lower for next
  layer.

- For running containers, they don't seem to care about syncing upper layer
  because if node goes down, they will simply throw away upper layer and
  create a fresh one.

So this patch provides a mount option "volatile" which disables all forms
of sync. Now it is caller's responsibility to throw away upper if system
crashes or shuts down and start fresh.

With "volatile", I am seeing roughly 20% speed up in my VM where I am just
installing emacs in an image. Installation time drops from 31 seconds to 25
seconds when nosync option is used. This is for the case of building on top
of an image where all packages are already cached. That way I take out the
network operations latency out of the measurement.

Giuseppe is also looking to cut down on number of iops done on the disk. He
is complaining that often in cloud their VMs are throttled if they cross
the limit. This option can help them where they reduce number of iops (by
cutting down on frequent sync and writebacks).

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-09-02 10:58:48 +02:00
Amir Goldstein
235ce9ed96 ovl: check for incompatible features in work dir
An incompatible feature is marked by a non-empty directory nested
2 levels deep under "work" dir, e.g.:
workdir/work/incompat/volatile.

This commit checks for marked incompat features, warns about them
and fails to mount the overlay, for example:
  overlayfs: overlay with incompat feature 'volatile' cannot be mounted

Very old kernels (i.e. v3.18) will fail to remove a non-empty "work"
dir and fail the mount.  Newer kernels will fail to remove a "work"
dir with entries nested 3 levels and fall back to read-only mount.

User mounting with old kernel will see a warning like these in dmesg:
  overlayfs: cleanup of 'incompat/...' failed (-39)
  overlayfs: cleanup of 'work/incompat' failed (-39)
  overlayfs: cleanup of 'ovl-work/work' failed (-39)
  overlayfs: failed to create directory /vdf/ovl-work/work (errno: 17);
             mounting read-only

These warnings should give the hint to the user that:
1. mount failure is caused by backward incompatible features
2. mount failure can be resolved by manually removing the "work" directory

There is nothing preventing users on old kernels from manually removing
workdir entirely or mounting overlay with a new workdir, so this is in
no way a full proof backward compatibility enforcement, but only a best
effort.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-09-02 10:58:48 +02:00
Linus Torvalds
99ea1521a0 Remove uninitialized_var() macro for v5.9-rc1
- Clean up non-trivial uses of uninitialized_var()
 - Update documentation and checkpatch for uninitialized_var() removal
 - Treewide removal of uninitialized_var()
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Merge tag 'uninit-macro-v5.9-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux

Pull uninitialized_var() macro removal from Kees Cook:
 "This is long overdue, and has hidden too many bugs over the years. The
  series has several "by hand" fixes, and then a trivial treewide
  replacement.

   - Clean up non-trivial uses of uninitialized_var()

   - Update documentation and checkpatch for uninitialized_var() removal

   - Treewide removal of uninitialized_var()"

* tag 'uninit-macro-v5.9-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
  compiler: Remove uninitialized_var() macro
  treewide: Remove uninitialized_var() usage
  checkpatch: Remove awareness of uninitialized_var() macro
  mm/debug_vm_pgtable: Remove uninitialized_var() usage
  f2fs: Eliminate usage of uninitialized_var() macro
  media: sur40: Remove uninitialized_var() usage
  KVM: PPC: Book3S PR: Remove uninitialized_var() usage
  clk: spear: Remove uninitialized_var() usage
  clk: st: Remove uninitialized_var() usage
  spi: davinci: Remove uninitialized_var() usage
  ide: Remove uninitialized_var() usage
  rtlwifi: rtl8192cu: Remove uninitialized_var() usage
  b43: Remove uninitialized_var() usage
  drbd: Remove uninitialized_var() usage
  x86/mm/numa: Remove uninitialized_var() usage
  docs: deprecated.rst: Add uninitialized_var()
2020-08-04 13:49:43 -07:00
Kees Cook
3f649ab728 treewide: Remove uninitialized_var() usage
Using uninitialized_var() is dangerous as it papers over real bugs[1]
(or can in the future), and suppresses unrelated compiler warnings
(e.g. "unused variable"). If the compiler thinks it is uninitialized,
either simply initialize the variable or make compiler changes.

In preparation for removing[2] the[3] macro[4], remove all remaining
needless uses with the following script:

git grep '\buninitialized_var\b' | cut -d: -f1 | sort -u | \
	xargs perl -pi -e \
		's/\buninitialized_var\(([^\)]+)\)/\1/g;
		 s:\s*/\* (GCC be quiet|to make compiler happy) \*/$::g;'

drivers/video/fbdev/riva/riva_hw.c was manually tweaked to avoid
pathological white-space.

No outstanding warnings were found building allmodconfig with GCC 9.3.0
for x86_64, i386, arm64, arm, powerpc, powerpc64le, s390x, mips, sparc64,
alpha, and m68k.

[1] https://lore.kernel.org/lkml/20200603174714.192027-1-glider@google.com/
[2] https://lore.kernel.org/lkml/CA+55aFw+Vbj0i=1TGqCR5vQkCzWJ0QxK6CernOU6eedsudAixw@mail.gmail.com/
[3] https://lore.kernel.org/lkml/CA+55aFwgbgqhbp1fkxvRKEpzyR5J8n1vKT1VZdz9knmPuXhOeg@mail.gmail.com/
[4] https://lore.kernel.org/lkml/CA+55aFz2500WfbKXAx8s67wrm9=yVJu65TpLgN_ybYNv0VEOKA@mail.gmail.com/

Reviewed-by: Leon Romanovsky <leonro@mellanox.com> # drivers/infiniband and mlx4/mlx5
Acked-by: Jason Gunthorpe <jgg@mellanox.com> # IB
Acked-by: Kalle Valo <kvalo@codeaurora.org> # wireless drivers
Reviewed-by: Chao Yu <yuchao0@huawei.com> # erofs
Signed-off-by: Kees Cook <keescook@chromium.org>
2020-07-16 12:35:15 -07:00
Amir Goldstein
4518dfcf76 ovl: fix lookup of indexed hardlinks with metacopy
We recently moved setting inode flag OVL_UPPERDATA to ovl_lookup().

When looking up an overlay dentry, upperdentry may be found by index
and not by name.  In that case, we fail to read the metacopy xattr
and falsly set the OVL_UPPERDATA on the overlay inode.

This caused a regression in xfstest overlay/033 when run with
OVERLAY_MOUNT_OPTIONS="-o metacopy=on".

Fixes: 28166ab3c8 ("ovl: initialize OVL_UPPERDATA in ovl_lookup()")
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-07-16 07:24:47 +02:00
Amir Goldstein
81a33c1ee9 ovl: fix unneeded call to ovl_change_flags()
The check if user has changed the overlay file was wrong, causing unneeded
call to ovl_change_flags() including taking f_lock on every file access.

Fixes: d989903058 ("ovl: do not generate duplicate fsnotify events for "fake" path")
Cc: <stable@vger.kernel.org> # v4.19+
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-07-16 07:24:47 +02:00
Amir Goldstein
f0e1266ed2 ovl: fix mount option checks for nfs_export with no upperdir
Without upperdir mount option, there is no index dir and the dependency
checks nfs_export => index for mount options parsing are incorrect.

Allow the combination nfs_export=on,index=off with no upperdir and move
the check for dependency redirect_dir=nofollow for non-upper mount case
to mount options parsing.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-07-16 00:11:15 +02:00
Amir Goldstein
470c156361 ovl: force read-only sb on failure to create index dir
With index feature enabled, on failure to create index dir, overlay is
being mounted read-only.  However, we do not forbid user to remount overlay
read-write.  Fix that by setting ofs->workdir to NULL, which prevents
remount read-write.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-07-16 00:11:15 +02:00
Amir Goldstein
a888db3101 ovl: fix regression with re-formatted lower squashfs
Commit 9df085f3c9 ("ovl: relax requirement for non null uuid of lower
fs") relaxed the requirement for non null uuid with single lower layer to
allow enabling index and nfs_export features with single lower squashfs.

Fabian reported a regression in a setup when overlay re-uses an existing
upper layer and re-formats the lower squashfs image.  Because squashfs
has no uuid, the origin xattr in upper layer are decoded from the new
lower layer where they may resolve to a wrong origin file and user may
get an ESTALE or EIO error on lookup.

To avoid the reported regression while still allowing the new features
with single lower squashfs, do not allow decoding origin with lower null
uuid unless user opted-in to one of the new features that require
following the lower inode of non-dir upper (index, xino, metacopy).

Reported-by: Fabian <godi.beat@gmx.net>
Link: https://lore.kernel.org/linux-unionfs/32532923.JtPX5UtSzP@fgdesktop/
Fixes: 9df085f3c9 ("ovl: relax requirement for non null uuid of lower fs")
Cc: stable@vger.kernel.org # v4.20+
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-07-16 00:10:31 +02:00