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I don't see an obvious reason why the upper 32 bit check needs to be
open-coded this way. Switch to upper_32_bits() which is more idiomatic and
should conceptually be the same check.
Cc: Amir Goldstein <amir73il@gmail.com>
Cc: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20210325083742.2334933-1-brauner@kernel.org
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Jan Kara <jack@suse.cz>
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Add limited support for unprivileged fanotify groups.
An unprivileged users is not allowed to get an open file descriptor in
the event nor the process pid of another process. An unprivileged user
cannot request permission events, cannot set mount/filesystem marks and
cannot request unlimited queue/marks.
This enables the limited functionality similar to inotify when watching a
set of files and directories for OPEN/ACCESS/MODIFY/CLOSE events, without
requiring SYS_CAP_ADMIN privileges.
The FAN_REPORT_DFID_NAME init flag, provide a method for an unprivileged
listener watching a set of directories (with FAN_EVENT_ON_CHILD) to monitor
all changes inside those directories.
This typically requires that the listener keeps a map of watched directory
fid to dirfd (O_PATH), where fid is obtained with name_to_handle_at()
before starting to watch for changes.
When getting an event, the reported fid of the parent should be resolved
to dirfd and fstatsat(2) with dirfd and name should be used to query the
state of the filesystem entry.
Link: https://lore.kernel.org/r/20210304112921.3996419-3-amir73il@gmail.com
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
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fanotify has some hardcoded limits. The only APIs to escape those limits
are FAN_UNLIMITED_QUEUE and FAN_UNLIMITED_MARKS.
Allow finer grained tuning of the system limits via sysfs tunables under
/proc/sys/fs/fanotify, similar to tunables under /proc/sys/fs/inotify,
with some minor differences.
- max_queued_events - global system tunable for group queue size limit.
Like the inotify tunable with the same name, it defaults to 16384 and
applies on initialization of a new group.
- max_user_marks - user ns tunable for marks limit per user.
Like the inotify tunable named max_user_watches, on a machine with
sufficient RAM and it defaults to 1048576 in init userns and can be
further limited per containing user ns.
- max_user_groups - user ns tunable for number of groups per user.
Like the inotify tunable named max_user_instances, it defaults to 128
in init userns and can be further limited per containing user ns.
The slightly different tunable names used for fanotify are derived from
the "group" and "mark" terminology used in the fanotify man pages and
throughout the code.
Considering the fact that the default value for max_user_instances was
increased in kernel v5.10 from 8192 to 1048576, leaving the legacy
fanotify limit of 8192 marks per group in addition to the max_user_marks
limit makes little sense, so the per group marks limit has been removed.
Note that when a group is initialized with FAN_UNLIMITED_MARKS, its own
marks are not accounted in the per user marks account, so in effect the
limit of max_user_marks is only for the collection of groups that are
not initialized with FAN_UNLIMITED_MARKS.
Link: https://lore.kernel.org/r/20210304112921.3996419-2-amir73il@gmail.com
Suggested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
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In order to improve event merge performance, hash events in a 128 size
hash table by the event merge key.
The fanotify_event size grows by two pointers, but we just reduced its
size by removing the objectid member, so overall its size is increased
by one pointer.
Permission events and overflow event are not merged so they are also
not hashed.
Link: https://lore.kernel.org/r/20210304104826.3993892-5-amir73il@gmail.com
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
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Current code has an assumtion that fsnotify_notify_queue_is_empty() is
called to verify that queue is not empty before trying to peek or remove
an event from queue.
Remove this assumption by moving the fsnotify_notify_queue_is_empty()
into the functions, allow them to return NULL value and check return
value by all callers.
This is a prep patch for multi event queues.
Link: https://lore.kernel.org/r/20210304104826.3993892-2-amir73il@gmail.com
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
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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:
https://git.kernel.org/brauner/man-pages/c/1d7b902e2875a1ff342e036a9f866a995640aea8
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
...
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git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs
Pull fsnotify update from Jan Kara:
"Make inotify groups be charged against appropriate memcgs"
* tag 'fsnotify_for_v5.12-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs:
inotify, memcg: account inotify instances to kmemcg
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Add two simple helpers to check permissions on a file and path
respectively and convert over some callers. It simplifies quite a few
codepaths and also reduces the churn in later patches quite a bit.
Christoph also correctly points out that this makes codepaths (e.g.
ioctls) way easier to follow that would otherwise have to do more
complex argument passing than necessary.
Link: https://lore.kernel.org/r/20210121131959.646623-4-christian.brauner@ubuntu.com
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Suggested-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: James Morris <jamorris@linux.microsoft.com>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
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Currently the fs sysctl inotify/max_user_instances is used to limit the
number of inotify instances on the system. For systems running multiple
workloads, the per-user namespace sysctl max_inotify_instances can be
used to further partition inotify instances. However there is no easy
way to set a sensible system level max limit on inotify instances and
further partition it between the workloads. It is much easier to charge
the underlying resource (i.e. memory) behind the inotify instances to
the memcg of the workload and let their memory limits limit the number
of inotify instances they can create.
With inotify instances charged to memcg, the admin can simply set
max_user_instances to INT_MAX and let the memcg limits of the jobs limit
their inotify instances.
Link: https://lore.kernel.org/r/20201220044608.1258123-1-shakeelb@google.com
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Shakeel Butt <shakeelb@google.com>
Signed-off-by: Jan Kara <jack@suse.cz>
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Commit
121b32a58a3a ("x86/entry/32: Use IA32-specific wrappers for syscalls taking 64-bit arguments")
converted native x86-32 which take 64-bit arguments to use the
compat handlers to allow conversion to passing args via pt_regs.
sys_fanotify_mark() was however missed, as it has a general compat
handler. Add a config option that will use the syscall wrapper that
takes the split args for native 32-bit.
[ bp: Fix typo in Kconfig help text. ]
Fixes: 121b32a58a3a ("x86/entry/32: Use IA32-specific wrappers for syscalls taking 64-bit arguments")
Reported-by: Paweł Jasiak <pawel@jasiak.xyz>
Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Jan Kara <jack@suse.cz>
Acked-by: Andy Lutomirski <luto@kernel.org>
Link: https://lkml.kernel.org/r/20201130223059.101286-1-brgerst@gmail.com
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Replace the existing /* fall through */ comments and its variants with
the new pseudo-keyword macro fallthrough[1]. Also, remove unnecessary
fall-through markings when it is the case.
[1] https://www.kernel.org/doc/html/v5.7/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
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Add support for FAN_REPORT_FID | FAN_REPORT_DIR_FID.
Internally, it is implemented as a private case of reporting both
parent and child fids and name, the parent and child fids are recorded
in a variable length fanotify_name_event, but there is no name.
It should be noted that directory modification events are recorded
in fixed size fanotify_fid_event when not reporting name, just like
with group flags FAN_REPORT_FID.
Link: https://lore.kernel.org/r/20200716084230.30611-23-amir73il@gmail.com
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
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For a group with fanotify_init() flag FAN_REPORT_DFID_NAME, the parent
fid and name are reported for events on non-directory objects with an
info record of type FAN_EVENT_INFO_TYPE_DFID_NAME.
If the group also has the init flag FAN_REPORT_FID, the child fid
is also reported with another info record that follows the first info
record. The second info record is the same info record that would have
been reported to a group with only FAN_REPORT_FID flag.
When the child fid needs to be recorded, the variable size struct
fanotify_name_event is preallocated with enough space to store the
child fh between the dir fh and the name.
Link: https://lore.kernel.org/r/20200716084230.30611-22-amir73il@gmail.com
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
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Introduce a new fanotify_init() flag FAN_REPORT_NAME. It requires the
flag FAN_REPORT_DIR_FID and there is a constant for setting both flags
named FAN_REPORT_DFID_NAME.
For a group with flag FAN_REPORT_NAME, the parent fid and name are
reported for directory entry modification events (create/detete/move)
and for events on non-directory objects.
Events on directories themselves are reported with their own fid and
"." as the name.
The parent fid and name are reported with an info record of type
FAN_EVENT_INFO_TYPE_DFID_NAME, similar to the way that parent fid is
reported with into type FAN_EVENT_INFO_TYPE_DFID, but with an appended
null terminated name string.
Link: https://lore.kernel.org/r/20200716084230.30611-21-amir73il@gmail.com
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
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In a group with flag FAN_REPORT_DIR_FID, when adding an inode mark with
FAN_EVENT_ON_CHILD, events on non-directory children are reported with
the fid of the parent.
When adding a filesystem or mount mark or mark on a non-dir inode, we
want to report events that are "possible on child" (e.g. open/close)
also with fid of the parent, as if the victim inode's parent is
interested in events "on child".
Some events, currently only FAN_MOVE_SELF, should be reported to a
sb/mount/non-dir mark with parent fid even though they are not
reported to a watching parent.
To get the desired behavior we set the flag FAN_EVENT_ON_CHILD on
all the sb/mount/non-dir mark masks in a group with FAN_REPORT_DIR_FID.
Link: https://lore.kernel.org/r/20200716084230.30611-20-amir73il@gmail.com
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
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For now, the flag is mutually exclusive with FAN_REPORT_FID.
Events include a single info record of type FAN_EVENT_INFO_TYPE_DFID
with a directory file handle.
For now, events are only reported for:
- Directory modification events
- Events on children of a watching directory
- Events on directory objects
Soon, we will add support for reporting the parent directory fid
for events on non-directories with filesystem/mount mark and
support for reporting both parent directory fid and child fid.
Link: https://lore.kernel.org/r/20200716084230.30611-19-amir73il@gmail.com
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
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An fanotify event name is always recorded relative to a dir fh.
Encapsulate the name_len member of fanotify_name_event in a new struct
fanotify_info, which describes the parceling of the variable size
buffer of an fanotify_name_event.
The dir_fh member of fanotify_name_event is renamed to _dir_fh and is not
accessed directly, but via the fanotify_info_dir_fh() accessor.
Although the dir_fh len information is already available in struct
fanotify_fh, we store it also in dif_fh_totlen member of fanotify_info,
including the size of fanotify_fh header, so we know the offset of the
name in the buffer without looking inside the dir_fh.
We also add a file_fh_totlen member to allow packing another file handle
in the variable size buffer after the dir_fh and before the name.
We are going to use that space to store the child fid.
Link: https://lore.kernel.org/r/20200716084230.30611-10-amir73il@gmail.com
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
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Up to now, fanotify allowed to set the FAN_EVENT_ON_CHILD flag on
sb/mount marks and non-directory inode mask, but the flag was ignored.
Mask out the flag if it is provided by user on sb/mount/non-dir marks
and define it as an implicit flag that cannot be removed by user.
This flag is going to be used internally to request for events with
parent and name info.
Link: https://lore.kernel.org/r/20200716084230.30611-8-amir73il@gmail.com
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
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So far, all flags that can be set in an fanotify mark mask can be set
explicitly by a call to fanotify_mark(2).
Prepare for defining implicit event flags that cannot be set by user with
fanotify_mark(2), similar to how inotify/dnotify implicitly set the
FS_EVENT_ON_CHILD flag.
Implicit event flags cannot be removed by user and mark gets destroyed
when only implicit event flags remain in the mask.
Link: https://lore.kernel.org/r/20200716084230.30611-7-amir73il@gmail.com
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
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The special event flags (FAN_ONDIR, FAN_EVENT_ON_CHILD) never had
any meaning in ignored mask. Mask them out explicitly.
Link: https://lore.kernel.org/r/20200716084230.30611-6-amir73il@gmail.com
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
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As preparation for new flags that report fids, define a bit set
of flags for a group reporting fids, currently containing the
only bit FAN_REPORT_FID.
Link: https://lore.kernel.org/r/20200716084230.30611-5-amir73il@gmail.com
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
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The special overflow event is allocated as struct fanotify_path_event,
but with a null path.
Use a special event type to identify the overflow event, so the helper
fanotify_has_event_path() will always indicate a non null path.
Allocating the overflow event doesn't need any of the fancy stuff in
fanotify_alloc_event(), so create a simplified helper for allocating the
overflow event.
There is also no need to store and report the pid with an overflow event.
Link: https://lore.kernel.org/r/20200708111156.24659-7-amir73il@gmail.com
Suggested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
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When user provides large buffer for events and there are lots of events
available, we can try to copy them all to userspace without scheduling
which can softlockup the kernel (furthermore exacerbated by the
contention on notification_lock). Add a scheduling point after copying
each event.
Note that usually the real underlying problem is the cost of fanotify
event merging and the resulting contention on notification_lock but this
is a cheap way to somewhat reduce the problem until we can properly
address that.
Reported-by: Francesco Ruggeri <fruggeri@arista.com>
Link: https://lore.kernel.org/lkml/20200714025417.A25EB95C0339@us180.sjc.aristanetworks.com
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
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fanotify_write() only aligned copy_from_user size to sizeof(response)
for higher values. This patch avoids all values below as suggested
by Amir Goldstein and set to response size unconditionally.
Link: https://lore.kernel.org/r/20200512181921.405973-1-fabf@skynet.be
Signed-off-by: Fabian Frederick <fabf@skynet.be>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
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fill_event_metadata() was removed in commit bb2f7b4542c7
("fanotify: open code fill_event_metadata()")
Link: https://lore.kernel.org/r/20200512181836.405879-1-fabf@skynet.be
Signed-off-by: Fabian Frederick <fabf@skynet.be>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
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Report event FAN_DIR_MODIFY with name in a variable length record similar
to how fid's are reported. With name info reporting implemented, setting
FAN_DIR_MODIFY in mark mask is now allowed.
When events are reported with name, the reported fid identifies the
directory and the name follows the fid. The info record type for this
event info is FAN_EVENT_INFO_TYPE_DFID_NAME.
For now, all reported events have at most one info record which is
either FAN_EVENT_INFO_TYPE_FID or FAN_EVENT_INFO_TYPE_DFID_NAME (for
FAN_DIR_MODIFY). Later on, events "on child" will report both records.
There are several ways that an application can use this information:
1. When watching a single directory, the name is always relative to
the watched directory, so application need to fstatat(2) the name
relative to the watched directory.
2. When watching a set of directories, the application could keep a map
of dirfd for all watched directories and hash the map by fid obtained
with name_to_handle_at(2). When getting a name event, the fid in the
event info could be used to lookup the base dirfd in the map and then
call fstatat(2) with that dirfd.
3. When watching a filesystem (FAN_MARK_FILESYSTEM) or a large set of
directories, the application could use open_by_handle_at(2) with the fid
in event info to obtain dirfd for the directory where event happened and
call fstatat(2) with this dirfd.
The last option scales better for a large number of watched directories.
The first two options may be available in the future also for non
privileged fanotify watchers, because open_by_handle_at(2) requires
the CAP_DAC_READ_SEARCH capability.
Link: https://lore.kernel.org/r/20200319151022.31456-15-amir73il@gmail.com
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
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For FAN_DIR_MODIFY event, allocate a variable size event struct to store
the dir entry name along side the directory file handle.
At this point, name info reporting is not yet implemented, so trying to
set FAN_DIR_MODIFY in mark mask will return -EINVAL.
Link: https://lore.kernel.org/r/20200319151022.31456-14-amir73il@gmail.com
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
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When some events have directory id and some object id,
fanotify_event_has_fid() becomes mostly useless and confusing because we
usually need to know which type of file handle the event has. So just
drop the function and use fanotify_event_object_fh() instead.
Signed-off-by: Jan Kara <jack@suse.cz>
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For some events, we are going to report both child and parent fid's,
so pass fsid and file handle as arguments to copy_fid_to_user(),
which is going to be called with parent and child file handles.
Link: https://lore.kernel.org/r/20200319151022.31456-13-amir73il@gmail.com
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
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Breakup the union and make them both inherit from abstract fanotify_event.
fanotify_path_event, fanotify_fid_event and fanotify_perm_event inherit
from fanotify_event.
type field in abstract fanotify_event determines the concrete event type.
fanotify_path_event, fanotify_fid_event and fanotify_perm_event are
allocated from separate memcache pools.
Rename fanotify_perm_event casting macro to FANOTIFY_PERM(), so that
FANOTIFY_PE() and FANOTIFY_FE() can be used as casting macros to
fanotify_path_event and fanotify_fid_event.
[JK: Cleanup FANOTIFY_PE() and FANOTIFY_FE() to be proper inline
functions and remove requirement that fanotify_event is the first in
event structures]
Link: https://lore.kernel.org/r/20200319151022.31456-11-amir73il@gmail.com
Suggested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
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Currently, struct fanotify_fid groups fsid and file handle and is
unioned together with struct path to save space. Also there is fh_type
and fh_len directly in struct fanotify_event to avoid padding overhead.
In the follwing patches, we will be adding more event types and this
packing makes code difficult to follow. So unpack everything and create
struct fanotify_fh which groups members logically related to file handle
to make code easier to follow. In the following patch we will pack
things again differently to make events smaller.
Signed-off-by: Jan Kara <jack@suse.cz>
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create_fd() is never used with invalid path. Also the only thing it
needs to know from fanotify_event is the path. Simplify the function to
take path directly and assume it is correct.
Signed-off-by: Jan Kara <jack@suse.cz>
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The .ioctl and .compat_ioctl file operations have the same prototype so
they can both point to the same function, which works great almost all
the time when all the commands are compatible.
One exception is the s390 architecture, where a compat pointer is only
31 bit wide, and converting it into a 64-bit pointer requires calling
compat_ptr(). Most drivers here will never run in s390, but since we now
have a generic helper for it, it's easy enough to use it consistently.
I double-checked all these drivers to ensure that all ioctl arguments
are used as pointers or are ignored, but are not interpreted as integer
values.
Acked-by: Jason Gunthorpe <jgg@mellanox.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: David Sterba <dsterba@suse.com>
Acked-by: Darren Hart (VMware) <dvhart@infradead.org>
Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Acked-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Acked-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
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git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux
Pull selinux updates from Paul Moore:
- Add LSM hooks, and SELinux access control hooks, for dnotify,
fanotify, and inotify watches. This has been discussed with both the
LSM and fs/notify folks and everybody is good with these new hooks.
- The LSM stacking changes missed a few calls to current_security() in
the SELinux code; we fix those and remove current_security() for
good.
- Improve our network object labeling cache so that we always return
the object's label, even when under memory pressure. Previously we
would return an error if we couldn't allocate a new cache entry, now
we always return the label even if we can't create a new cache entry
for it.
- Convert the sidtab atomic_t counter to a normal u32 with
READ/WRITE_ONCE() and memory barrier protection.
- A few patches to policydb.c to clean things up (remove forward
declarations, long lines, bad variable names, etc)
* tag 'selinux-pr-20190917' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux:
lsm: remove current_security()
selinux: fix residual uses of current_security() for the SELinux blob
selinux: avoid atomic_t usage in sidtab
fanotify, inotify, dnotify, security: add security hook for fs notifications
selinux: always return a secid from the network caches if we find one
selinux: policydb - rename type_val_to_struct_array
selinux: policydb - fix some checkpatch.pl warnings
selinux: shuffle around policydb.c to get rid of forward declarations
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As of now, setting watches on filesystem objects has, at most, applied a
check for read access to the inode, and in the case of fanotify, requires
CAP_SYS_ADMIN. No specific security hook or permission check has been
provided to control the setting of watches. Using any of inotify, dnotify,
or fanotify, it is possible to observe, not only write-like operations, but
even read access to a file. Modeling the watch as being merely a read from
the file is insufficient for the needs of SELinux. This is due to the fact
that read access should not necessarily imply access to information about
when another process reads from a file. Furthermore, fanotify watches grant
more power to an application in the form of permission events. While
notification events are solely, unidirectional (i.e. they only pass
information to the receiving application), permission events are blocking.
Permission events make a request to the receiving application which will
then reply with a decision as to whether or not that action may be
completed. This causes the issue of the watching application having the
ability to exercise control over the triggering process. Without drawing a
distinction within the permission check, the ability to read would imply
the greater ability to control an application. Additionally, mount and
superblock watches apply to all files within the same mount or superblock.
Read access to one file should not necessarily imply the ability to watch
all files accessed within a given mount or superblock.
In order to solve these issues, a new LSM hook is implemented and has been
placed within the system calls for marking filesystem objects with inotify,
fanotify, and dnotify watches. These calls to the hook are placed at the
point at which the target path has been resolved and are provided with the
path struct, the mask of requested notification events, and the type of
object on which the mark is being set (inode, superblock, or mount). The
mask and obj_type have already been translated into common FS_* values
shared by the entirety of the fs notification infrastructure. The path
struct is passed rather than just the inode so that the mount is available,
particularly for mount watches. This also allows for use of the hook by
pathname-based security modules. However, since the hook is intended for
use even by inode based security modules, it is not placed under the
CONFIG_SECURITY_PATH conditional. Otherwise, the inode-based security
modules would need to enable all of the path hooks, even though they do not
use any of them.
This only provides a hook at the point of setting a watch, and presumes
that permission to set a particular watch implies the ability to receive
all notification about that object which match the mask. This is all that
is required for SELinux. If other security modules require additional hooks
or infrastructure to control delivery of notification, these can be added
by them. It does not make sense for us to propose hooks for which we have
no implementation. The understanding that all notifications received by the
requesting application are all strictly of a type for which the application
has been granted permission shows that this implementation is sufficient in
its coverage.
Security modules wishing to provide complete control over fanotify must
also implement a security_file_open hook that validates that the access
requested by the watching application is authorized. Fanotify has the issue
that it returns a file descriptor with the file mode specified during
fanotify_init() to the watching process on event. This is already covered
by the LSM security_file_open hook if the security module implements
checking of the requested file mode there. Otherwise, a watching process
can obtain escalated access to a file for which it has not been authorized.
The selinux_path_notify hook implementation works by adding five new file
permissions: watch, watch_mount, watch_sb, watch_reads, and watch_with_perm
(descriptions about which will follow), and one new filesystem permission:
watch (which is applied to superblock checks). The hook then decides which
subset of these permissions must be held by the requesting application
based on the contents of the provided mask and the obj_type. The
selinux_file_open hook already checks the requested file mode and therefore
ensures that a watching process cannot escalate its access through
fanotify.
The watch, watch_mount, and watch_sb permissions are the baseline
permissions for setting a watch on an object and each are a requirement for
any watch to be set on a file, mount, or superblock respectively. It should
be noted that having either of the other two permissions (watch_reads and
watch_with_perm) does not imply the watch, watch_mount, or watch_sb
permission. Superblock watches further require the filesystem watch
permission to the superblock. As there is no labeled object in view for
mounts, there is no specific check for mount watches beyond watch_mount to
the inode. Such a check could be added in the future, if a suitable labeled
object existed representing the mount.
The watch_reads permission is required to receive notifications from
read-exclusive events on filesystem objects. These events include accessing
a file for the purpose of reading and closing a file which has been opened
read-only. This distinction has been drawn in order to provide a direct
indication in the policy for this otherwise not obvious capability. Read
access to a file should not necessarily imply the ability to observe read
events on a file.
Finally, watch_with_perm only applies to fanotify masks since it is the
only way to set a mask which allows for the blocking, permission event.
This permission is needed for any watch which is of this type. Though
fanotify requires CAP_SYS_ADMIN, this is insufficient as it gives implicit
trust to root, which we do not do, and does not support least privilege.
Signed-off-by: Aaron Goidel <acgoide@tycho.nsa.gov>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Acked-by: Jan Kara <jack@suse.cz>
Signed-off-by: Paul Moore <paul@paul-moore.com>
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Proc filesystem has special locking rules for various files. Thus
fanotify which opens files on event delivery can easily deadlock
against another process that waits for fanotify permission event to be
handled. Since permission events on /proc have doubtful value anyway,
just disallow them.
Link: https://lore.kernel.org/linux-fsdevel/20190320131642.GE9485@quack2.suse.cz/
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
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When file handle is embedded inside fanotify_event and usercopy checks
are enabled, we get a warning like:
Bad or missing usercopy whitelist? Kernel memory exposure attempt detected
from SLAB object 'fanotify_event' (offset 40, size 8)!
WARNING: CPU: 1 PID: 7649 at mm/usercopy.c:78 usercopy_warn+0xeb/0x110
mm/usercopy.c:78
Annotate handling in fanotify_event properly to mark copying it to
userspace is fine.
Reported-by: syzbot+2c49971e251e36216d1f@syzkaller.appspotmail.com
Fixes: a8b13aa20afb ("fanotify: enable FAN_REPORT_FID init flag")
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
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When waiting for response to fanotify permission events, we currently
use uninterruptible waits. That makes code simple however it can cause
lots of processes to end up in uninterruptible sleep with hard reboot
being the only alternative in case fanotify listener process stops
responding (e.g. due to a bug in its implementation). Uninterruptible
sleep also makes system hibernation fail if the listener gets frozen
before the process generating fanotify permission event.
Fix these problems by using interruptible sleep for waiting for response
to fanotify event. This is slightly tricky though - we have to
detect when the event got already reported to userspace as in that
case we must not free the event. Instead we push the responsibility for
freeing the event to the process that will write response to the
event.
Reported-by: Orion Poplawski <orion@nwra.com>
Reported-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
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Track whether permission event got already reported to userspace and
whether userspace already answered to the permission event. Protect
stores to this field together with updates to ->response field by
group->notification_lock. This will allow aborting wait for reply to
permission event from userspace.
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
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Simplify iteration cleaning access_list in fanotify_release(). That will
make following changes more obvious.
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
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get_one_event() has a single caller and that just locks
notification_lock around the call. Move locking inside get_one_event()
as that will make using ->response field for permission event state
easier.
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
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Fold dequeue_event() into process_access_response(). This will make
changes to use of ->response field easier.
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
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Add support for events with data type FSNOTIFY_EVENT_INODE
(e.g. create/attrib/move/delete) for inode and filesystem mark types.
The "inode" events do not carry enough information (i.e. path) to
report event->fd, so we do not allow setting a mask for those events
unless group supports reporting fid.
The "inode" events are not supported on a mount mark, because they do
not carry enough information (i.e. path) to be filtered by mount point.
The "dirent" events (create/move/delete) report the fid of the parent
directory where events took place without specifying the filename of the
child. In the future, fanotify may get support for reporting filename
information for those events.
Cc: <linux-api@vger.kernel.org>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
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When event data type is FSNOTIFY_EVENT_INODE, we don't have a refernece
to the mount, so we will not be able to open a file descriptor when user
reads the event. However, if the listener has enabled reporting file
identifier with the FAN_REPORT_FID init flag, we allow reporting those
events and we use an identifier inode to encode fid.
The inode to use as identifier when reporting fid depends on the event.
For dirent modification events, we report the modified directory inode
and we report the "victim" inode otherwise.
For example:
FS_ATTRIB reports the child inode even if reported on a watched parent.
FS_CREATE reports the modified dir inode and not the created inode.
[JK: Fixup condition in fanotify_group_event_mask()]
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
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This is a cleanup that doesn't change any logic.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
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For FAN_REPORT_FID, we need to encode fid with fsid of the filesystem on
every event. To avoid having to call vfs_statfs() on every event to get
fsid, we store the fsid in fsnotify_mark_connector on the first time we
add a mark and on handle event we use the cached fsid.
Subsequent calls to add mark on the same object are expected to pass the
same fsid, so the call will fail on cached fsid mismatch.
If an event is reported on several mark types (inode, mount, filesystem),
all connectors should already have the same fsid, so we use the cached
fsid from the first connector.
[JK: Simplify code flow around fanotify_get_fid()
make fsid argument of fsnotify_add_mark_locked() unconditional]
Suggested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
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When setting up an fanotify listener, user may request to get fid
information in event instead of an open file descriptor.
The fid obtained with event on a watched object contains the file
handle returned by name_to_handle_at(2) and fsid returned by statfs(2).
Restrict FAN_REPORT_FID to class FAN_CLASS_NOTIF, because we have have
no good reason to support reporting fid on permission events.
When setting a mark, we need to make sure that the filesystem
supports encoding file handles with name_to_handle_at(2) and that
statfs(2) encodes a non-zero fsid.
Cc: <linux-api@vger.kernel.org>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
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If group requested FAN_REPORT_FID and event has file identifier,
copy that information to user reading the event after event metadata.
fid information is formatted as struct fanotify_event_info_fid
that includes a generic header struct fanotify_event_info_header,
so that other info types could be defined in the future using the
same header.
metadata->event_len includes the length of the fid information.
The fid information includes the filesystem's fsid (see statfs(2))
followed by an NFS file handle of the file that could be passed as
an argument to open_by_handle_at(2).
Cc: <linux-api@vger.kernel.org>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
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When user requests the flag FAN_REPORT_FID in fanotify_init(),
a unique file identifier of the event target object will be reported
with the event.
The file identifier includes the filesystem's fsid (i.e. from statfs(2))
and an NFS file handle of the file (i.e. from name_to_handle_at(2)).
The file identifier makes holding the path reference and passing a file
descriptor to user redundant, so those are disabled in a group with
FAN_REPORT_FID.
Encode fid and store it in event for a group with FAN_REPORT_FID.
Up to 12 bytes of file handle on 32bit arch (16 bytes on 64bit arch)
are stored inline in fanotify_event struct. Larger file handles are
stored in an external allocated buffer.
On failure to encode fid, we print a warning and queue the event
without the fid information.
[JK: Fold part of later patched into this one to use
exportfs_encode_inode_fh() right away]
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
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The helper is quite trivial and open coding it will make it easier
to implement copying event fid info to user.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
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