linux-stable.git/fs/namespace.c, branch v5.2

vfs: move_mount: reject moving kernel internal mounts

2019-07-01T14:46:36+00:00

sys_move_mount() crashes by dereferencing the pointer MNT_NS_INTERNAL,
a.k.a. ERR_PTR(-EINVAL), if the old mount is specified by fd for a
kernel object with an internal mount, such as a pipe or memfd.

Fix it by checking for this case and returning -EINVAL.

[AV: what we want is is_mounted(); use that instead of making the
condition even more convoluted]

Reproducer:

    #include 

    #define __NR_move_mount         429
    #define MOVE_MOUNT_F_EMPTY_PATH 0x00000004

    int main()
    {
    	int fds[2];

    	pipe(fds);
        syscall(__NR_move_mount, fds[0], "", -1, "/", MOVE_MOUNT_F_EMPTY_PATH);
    }

Reported-by: syzbot+6004acbaa1893ad013f0@syzkaller.appspotmail.com
Fixes: 2db154b3ea8e ("vfs: syscall: Add move_mount(2) to move mounts around")
Signed-off-by: Eric Biggers 
Signed-off-by: Al Viro

fs/namespace: fix unprivileged mount propagation

2019-06-17T21:36:09+00:00

When propagating mounts across mount namespaces owned by different user
namespaces it is not possible anymore to move or umount the mount in the
less privileged mount namespace.

Here is a reproducer:

  sudo mount -t tmpfs tmpfs /mnt
  sudo --make-rshared /mnt

  # create unprivileged user + mount namespace and preserve propagation
  unshare -U -m --map-root --propagation=unchanged

  # now change back to the original mount namespace in another terminal:
  sudo mkdir /mnt/aaa
  sudo mount -t tmpfs tmpfs /mnt/aaa

  # now in the unprivileged user + mount namespace
  mount --move /mnt/aaa /opt

Unfortunately, this is a pretty big deal for userspace since this is
e.g. used to inject mounts into running unprivileged containers.
So this regression really needs to go away rather quickly.

The problem is that a recent change falsely locked the root of the newly
added mounts by setting MNT_LOCKED. Fix this by only locking the mounts
on copy_mnt_ns() and not when adding a new mount.

Fixes: 3bd045cc9c4b ("separate copying and locking mount tree on cross-userns copies")
Cc: Linus Torvalds 
Cc: Al Viro 
Cc: 
Tested-by: Christian Brauner 
Acked-by: Christian Brauner 
Signed-off-by: "Eric W. Biederman" 
Signed-off-by: Christian Brauner 
Signed-off-by: Al Viro

vfs: fsmount: add missing mntget()

2019-06-17T21:36:07+00:00

sys_fsmount() needs to take a reference to the new mount when adding it
to the anonymous mount namespace.  Otherwise the filesystem can be
unmounted while it's still in use, as found by syzkaller.

Reported-by: Mark Rutland 
Reported-by: syzbot+99de05d099a170867f22@syzkaller.appspotmail.com
Reported-by: syzbot+7008b8b8ba7df475fdc8@syzkaller.appspotmail.com
Fixes: 93766fbd2696 ("vfs: syscall: Add fsmount() to create a mount for a superblock")
Signed-off-by: Eric Biggers 
Signed-off-by: Al Viro

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 209

2019-05-30T18:29:53+00:00

Based on 1 normalized pattern(s):

  released under gpl v2

extracted by the scancode license scanner the SPDX license identifier

  GPL-2.0-only

has been chosen to replace the boilerplate/reference in 15 file(s).

Signed-off-by: Thomas Gleixner 
Reviewed-by: Steve Winslow 
Reviewed-by: Allison Randal 
Reviewed-by: Alexios Zavras 
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190528171438.895196075@linutronix.de
Signed-off-by: Greg Kroah-Hartman

do_move_mount(): fix an unsafe use of is_anon_ns()

2019-05-09T06:32:50+00:00

What triggers it is a race between mount --move and umount -l
of the source; we should reject it (the source is parentless *and*
not the root of anon namespace at that), but the check for namespace
being an anon one is broken in that case - is_anon_ns() needs
ns to be non-NULL.  Better fixed here than in is_anon_ns(), since
the rest of the callers is guaranteed to get a non-NULL argument...

Reported-by: syzbot+494c7ddf66acac0ad747@syzkaller.appspotmail.com
Signed-off-by: Al Viro

vfs: syscall: Add fsmount() to create a mount for a superblock

2019-03-20T22:49:06+00:00

Provide a system call by which a filesystem opened with fsopen() and
configured by a series of fsconfig() calls can have a detached mount object
created for it.  This mount object can then be attached to the VFS mount
hierarchy using move_mount() by passing the returned file descriptor as the
from directory fd.

The system call looks like:

	int mfd = fsmount(int fsfd, unsigned int flags,
			  unsigned int attr_flags);

where fsfd is the file descriptor returned by fsopen().  flags can be 0 or
FSMOUNT_CLOEXEC.  attr_flags is a bitwise-OR of the following flags:

	MOUNT_ATTR_RDONLY	Mount read-only
	MOUNT_ATTR_NOSUID	Ignore suid and sgid bits
	MOUNT_ATTR_NODEV	Disallow access to device special files
	MOUNT_ATTR_NOEXEC	Disallow program execution
	MOUNT_ATTR__ATIME	Setting on how atime should be updated
	MOUNT_ATTR_RELATIME	- Update atime relative to mtime/ctime
	MOUNT_ATTR_NOATIME	- Do not update access times
	MOUNT_ATTR_STRICTATIME	- Always perform atime updates
	MOUNT_ATTR_NODIRATIME	Do not update directory access times

In the event that fsmount() fails, it may be possible to get an error
message by calling read() on fsfd.  If no message is available, ENODATA
will be reported.

Signed-off-by: David Howells 
cc: linux-api@vger.kernel.org
Signed-off-by: Al Viro

teach move_mount(2) to work with OPEN_TREE_CLONE

2019-03-20T22:49:06+00:00

Allow a detached tree created by open_tree(..., OPEN_TREE_CLONE) to be
attached by move_mount(2).

If by the time of final fput() of OPEN_TREE_CLONE-opened file its tree is
not detached anymore, it won't be dissolved.  move_mount(2) is adjusted
to handle detached source.

That gives us equivalents of mount --bind and mount --rbind.

Thanks also to Alan Jenkins  for
providing a whole bunch of ways to break things using this interface.

Signed-off-by: Al Viro 
Signed-off-by: David Howells 
Signed-off-by: Al Viro

vfs: syscall: Add move_mount(2) to move mounts around

2019-03-20T22:49:06+00:00

Add a move_mount() system call that will move a mount from one place to
another and, in the next commit, allow to attach an unattached mount tree.

The new system call looks like the following:

	int move_mount(int from_dfd, const char *from_path,
		       int to_dfd, const char *to_path,
		       unsigned int flags);

Signed-off-by: David Howells 
cc: linux-api@vger.kernel.org
Signed-off-by: Al Viro

vfs: syscall: Add open_tree(2) to reference or clone a mount

2019-03-20T22:49:06+00:00

open_tree(dfd, pathname, flags)

Returns an O_PATH-opened file descriptor or an error.
dfd and pathname specify the location to open, in usual
fashion (see e.g. fstatat(2)).  flags should be an OR of
some of the following:
	* AT_PATH_EMPTY, AT_NO_AUTOMOUNT, AT_SYMLINK_NOFOLLOW -
same meanings as usual
	* OPEN_TREE_CLOEXEC - make the resulting descriptor
close-on-exec
	* OPEN_TREE_CLONE or OPEN_TREE_CLONE | AT_RECURSIVE -
instead of opening the location in question, create a detached
mount tree matching the subtree rooted at location specified by
dfd/pathname.  With AT_RECURSIVE the entire subtree is cloned,
without it - only the part within in the mount containing the
location in question.  In other words, the same as mount --rbind
or mount --bind would've taken.  The detached tree will be
dissolved on the final close of obtained file.  Creation of such
detached trees requires the same capabilities as doing mount --bind.

Signed-off-by: Al Viro 
Signed-off-by: David Howells 
cc: linux-api@vger.kernel.org
Signed-off-by: Al Viro

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

2019-03-12T21:08:19+00:00

Pull vfs mount infrastructure updates from Al Viro:
 "The rest of core infrastructure; no new syscalls in that pile, but the
  old parts are switched to new infrastructure. At that point
  conversions of individual filesystems can happen independently; some
  are done here (afs, cgroup, procfs, etc.), there's also a large series
  outside of that pile dealing with NFS (quite a bit of option-parsing
  stuff is getting used there - it's one of the most convoluted
  filesystems in terms of mount-related logics), but NFS bits are the
  next cycle fodder.

  It got seriously simplified since the last cycle; documentation is
  probably the weakest bit at the moment - I considered dropping the
  commit introducing Documentation/filesystems/mount_api.txt (cutting
  the size increase by quarter ;-), but decided that it would be better
  to fix it up after -rc1 instead.

  That pile allows to do followup work in independent branches, which
  should make life much easier for the next cycle. fs/super.c size
  increase is unpleasant; there's a followup series that allows to
  shrink it considerably, but I decided to leave that until the next
  cycle"

* 'work.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (41 commits)
  afs: Use fs_context to pass parameters over automount
  afs: Add fs_context support
  vfs: Add some logging to the core users of the fs_context log
  vfs: Implement logging through fs_context
  vfs: Provide documentation for new mount API
  vfs: Remove kern_mount_data()
  hugetlbfs: Convert to fs_context
  cpuset: Use fs_context
  kernfs, sysfs, cgroup, intel_rdt: Support fs_context
  cgroup: store a reference to cgroup_ns into cgroup_fs_context
  cgroup1_get_tree(): separate "get cgroup_root to use" into a separate helper
  cgroup_do_mount(): massage calling conventions
  cgroup: stash cgroup_root reference into cgroup_fs_context
  cgroup2: switch to option-by-option parsing
  cgroup1: switch to option-by-option parsing
  cgroup: take options parsing into ->parse_monolithic()
  cgroup: fold cgroup1_mount() into cgroup1_get_tree()
  cgroup: start switching to fs_context
  ipc: Convert mqueue fs to fs_context
  proc: Add fs_context support to procfs
  ...