Unfortunately, there's userland code that used to rely upon these
checks being done before anything else to check for UMOUNT_NOFOLLOW
support. That broke in 41525f56e2 ("fs: refactor ksys_umount").
Separate those from the rest of checks and move them to ksys_umount();
unlike everything else in there, this can be sanely done there.
Reported-by: Sargun Dhillon <sargun@sargun.me>
Fixes: 41525f56e2 ("fs: refactor ksys_umount")
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Pull misc vfs updates from Al Viro:
"Assorted patches from previous cycle(s)..."
* 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
fix hostfs_open() use of ->f_path.dentry
Make sure that make_create_in_sticky() never sees uninitialized value of dir_mode
fs: Kill DCACHE_DONTCACHE dentry even if DCACHE_REFERENCED is set
fs: Handle I_DONTCACHE in iput_final() instead of generic_drop_inode()
fs/namespace.c: WARN if mnt_count has become negative
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Merge tag 'fixes-v5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux
Pull misc fixes from Christian Brauner:
"This contains several fixes which felt worth being combined into a
single branch:
- Use put_nsproxy() instead of open-coding it switch_task_namespaces()
- Kirill's work to unify lifecycle management for all namespaces. The
lifetime counters are used identically for all namespaces types.
Namespaces may of course have additional unrelated counters and
these are not altered. This work allows us to unify the type of the
counters and reduces maintenance cost by moving the counter in one
place and indicating that basic lifetime management is identical
for all namespaces.
- Peilin's fix adding three byte padding to Dmitry's
PTRACE_GET_SYSCALL_INFO uapi struct to prevent an info leak.
- Two smal patches to convert from the /* fall through */ comment
annotation to the fallthrough keyword annotation which I had taken
into my branch and into -next before df561f6688 ("treewide: Use
fallthrough pseudo-keyword") made it upstream which fixed this
tree-wide.
Since I didn't want to invalidate all testing for other commits I
didn't rebase and kept them"
* tag 'fixes-v5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux:
nsproxy: use put_nsproxy() in switch_task_namespaces()
sys: Convert to the new fallthrough notation
signal: Convert to the new fallthrough notation
time: Use generic ns_common::count
cgroup: Use generic ns_common::count
mnt: Use generic ns_common::count
user: Use generic ns_common::count
pid: Use generic ns_common::count
ipc: Use generic ns_common::count
uts: Use generic ns_common::count
net: Use generic ns_common::count
ns: Add a common refcount into ns_common
ptrace: Prevent kernel-infoleak in ptrace_get_syscall_info()
Missing calls to mntget() (or equivalently, too many calls to mntput())
are hard to detect because mntput() delays freeing mounts using
task_work_add(), then again using call_rcu(). As a result, mnt_count
can often be decremented to -1 without getting a KASAN use-after-free
report. Such cases are still bugs though, and they point to real
use-after-frees being possible.
For an example of this, see the bug fixed by commit 1b0b9cc8d3
("vfs: fsmount: add missing mntget()"), discussed at
https://lkml.kernel.org/linux-fsdevel/20190605135401.GB30925@xxxxxxxxxxxxxxxxxxxxxxxxx/T/#u.
This bug *should* have been trivial to find. But actually, it wasn't
found until syzkaller happened to use fchdir() to manipulate the
reference count just right for the bug to be noticeable.
Address this by making mntput_no_expire() issue a WARN if mnt_count has
become negative.
Suggested-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Pull misc vfs updates from Al Viro:
"Assorted stuff all over the place (the largest group here is
Christoph's stat cleanups)"
* 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
fs: remove KSTAT_QUERY_FLAGS
fs: remove vfs_stat_set_lookup_flags
fs: move vfs_fstatat out of line
fs: implement vfs_stat and vfs_lstat in terms of vfs_fstatat
fs: remove vfs_statx_fd
fs: omfs: use kmemdup() rather than kmalloc+memcpy
[PATCH] reduce boilerplate in fsid handling
fs: Remove duplicated flag O_NDELAY occurring twice in VALID_OPEN_FLAGS
selftests: mount: add nosymfollow tests
Add a "nosymfollow" mount option.
A previous commit changed the notification mode from true/false to an
int, allowing notify-no, notify-yes, or signal-notify. This was
backwards compatible in the sense that any existing true/false user
would translate to either 0 (on notification sent) or 1, the latter
which mapped to TWA_RESUME. TWA_SIGNAL was assigned a value of 2.
Clean this up properly, and define a proper enum for the notification
mode. Now we have:
- TWA_NONE. This is 0, same as before the original change, meaning no
notification requested.
- TWA_RESUME. This is 1, same as before the original change, meaning
that we use TIF_NOTIFY_RESUME.
- TWA_SIGNAL. This uses TIF_SIGPENDING/JOBCTL_TASK_WORK for the
notification.
Clean up all the callers, switching their 0/1/false/true to using the
appropriate TWA_* mode for notifications.
Fixes: e91b481623 ("task_work: teach task_work_add() to do signal_wake_up()")
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Pull compat mount cleanups from Al Viro:
"The last remnants of mount(2) compat buried by Christoph.
Buried into NFS, that is.
Generally I'm less enthusiastic about "let's use in_compat_syscall()
deep in call chain" kind of approach than Christoph seems to be, but
in this case it's warranted - that had been an NFS-specific wart,
hopefully not to be repeated in any other filesystems (read: any new
filesystem introducing non-text mount options will get NAKed even if
it doesn't mess the layout up).
IOW, not worth trying to grow an infrastructure that would avoid that
use of in_compat_syscall()..."
* 'compat.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
fs: remove compat_sys_mount
fs,nfs: lift compat nfs4 mount data handling into the nfs code
nfs: simplify nfs4_parse_monolithic
compat_sys_mount is identical to the regular sys_mount now, so remove it
and use the native version everywhere.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
The copy_mount_options() function takes a user pointer argument but no
size and it tries to read up to a PAGE_SIZE. However, copy_from_user()
is not guaranteed to return all the accessible bytes if, for example,
the access crosses a page boundary and gets a fault on the second page.
To work around this, the current copy_mount_options() implementation
performs two copy_from_user() passes, first to the end of the current
page and the second to what's left in the subsequent page.
On arm64 with MTE enabled, access to a user page may trigger a fault
after part of the buffer in a page has been copied (when the user
pointer tag, bits 56-59, no longer matches the allocation tag stored in
memory). Allow copy_mount_options() to handle such intra-page faults by
resorting to byte at a time copy in case of copy_from_user() failure.
Note that copy_from_user() handles the zeroing of the kernel buffer in
case of error.
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
For mounts that have the new "nosymfollow" option, don't follow symlinks
when resolving paths. The new option is similar in spirit to the
existing "nodev", "noexec", and "nosuid" options, as well as to the
LOOKUP_NO_SYMLINKS resolve flag in the openat2(2) syscall. Various BSD
variants have been supporting the "nosymfollow" mount option for a long
time with equivalent implementations.
Note that symlinks may still be created on file systems mounted with
the "nosymfollow" option present. readlink() remains functional, so
user space code that is aware of symlinks can still choose to follow
them explicitly.
Setting the "nosymfollow" mount option helps prevent privileged
writers from modifying files unintentionally in case there is an
unexpected link along the accessed path. The "nosymfollow" option is
thus useful as a defensive measure for systems that need to deal with
untrusted file systems in privileged contexts.
More information on the history and motivation for this patch can be
found here:
https://sites.google.com/a/chromium.org/dev/chromium-os/chromiumos-design-docs/hardening-against-malicious-stateful-data#TOC-Restricting-symlink-traversal
Signed-off-by: Mattias Nissler <mnissler@chromium.org>
Signed-off-by: Ross Zwisler <zwisler@google.com>
Reviewed-by: Aleksa Sarai <cyphar@cyphar.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Switch over mount namespaces to use the newly introduced common lifetime
counter.
Currently every namespace type has its own lifetime counter which is stored
in the specific namespace struct. The lifetime counters are used
identically for all namespaces types. Namespaces may of course have
additional unrelated counters and these are not altered.
This introduces a common lifetime counter into struct ns_common. The
ns_common struct encompasses information that all namespaces share. That
should include the lifetime counter since its common for all of them.
It also allows us to unify the type of the counters across all namespaces.
Most of them use refcount_t but one uses atomic_t and at least one uses
kref. Especially the last one doesn't make much sense since it's just a
wrapper around refcount_t since 2016 and actually complicates cleanup
operations by having to use container_of() to cast the correct namespace
struct out of struct ns_common.
Having the lifetime counter for the namespaces in one place reduces
maintenance cost. Not just because after switching all namespaces over we
will have removed more code than we added but also because the logic is
more easily understandable and we indicate to the user that the basic
lifetime requirements for all namespaces are currently identical.
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Link: https://lore.kernel.org/r/159644980287.604812.761686947449081169.stgit@localhost.localdomain
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Pull mount leak fix from Al Viro:
"Regression fix for the syscalls-for-init series - fix a leak of a 'struct path'"
* 'fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
fs: fix a struct path leak in path_umount
Make sure we also put the dentry and vfsmnt in the illegal flags
and !may_umount cases.
Fixes: 41525f56e2 ("fs: refactor ksys_umount")
Reported-by: Vikas Kumar <vikas.kumar2@arm.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Pull init and set_fs() cleanups from Al Viro:
"Christoph's 'getting rid of ksys_...() uses under KERNEL_DS' series"
* 'hch.init_path' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (50 commits)
init: add an init_dup helper
init: add an init_utimes helper
init: add an init_stat helper
init: add an init_mknod helper
init: add an init_mkdir helper
init: add an init_symlink helper
init: add an init_link helper
init: add an init_eaccess helper
init: add an init_chmod helper
init: add an init_chown helper
init: add an init_chroot helper
init: add an init_chdir helper
init: add an init_rmdir helper
init: add an init_unlink helper
init: add an init_umount helper
init: add an init_mount helper
init: mark create_dev as __init
init: mark console_on_rootfs as __init
init: initialize ramdisk_execute_command at compile time
devtmpfs: refactor devtmpfsd()
...
Like ksys_umount, but takes a kernel pointer for the destination path.
Switch over the umount in the init code, which just happen to work due to
the implicit set_fs(KERNEL_DS) during early init right now.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Like do_mount, but takes a kernel pointer for the destination path.
Switch over the mounts in the init code and devtmpfs to it, which
just happen to work due to the implicit set_fs(KERNEL_DS) during early
init right now.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Factor out a path_umount helper that takes a struct path * instead of the
actual file name. This will allow to convert the init and devtmpfs code
to properly mount based on a kernel pointer instead of relying on the
implicit set_fs(KERNEL_DS) during early init.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Factor out a path_mount helper that takes a struct path * instead of the
actual file name. This will allow to convert the init and devtmpfs code
to properly mount based on a kernel pointer instead of relying on the
implicit set_fs(KERNEL_DS) during early init.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Previous patch changed handling of remount/reconfigure to ignore all
options, including those that are unknown to the fuse kernel fs. This was
done for backward compatibility, but this likely only affects the old
mount(2) API.
The new fsconfig(2) based reconfiguration could possibly be improved. This
would make the new API less of a drop in replacement for the old, OTOH this
is a good chance to get rid of some weirdnesses in the old API.
Several other behaviors might make sense:
1) unknown options are rejected, known options are ignored
2) unknown options are rejected, known options are rejected if the value
is changed, allowed otherwise
3) all options are rejected
Prior to the backward compatibility fix to ignore all options all known
options were accepted (1), even if they change the value of a mount
parameter; fuse_reconfigure() does not look at the config values set by
fuse_parse_param().
To fix that we'd need to verify that the value provided is the same as set
in the initial configuration (2). The major drawback is that this is much
more complex than just rejecting all attempts at changing options (3);
i.e. all options signify initial configuration values and don't make sense
on reconfigure.
This patch opts for (3) with the rationale that no mount options are
reconfigurable in fuse.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Pull vfs fixes from Al Viro:
"A couple of trivial patches that fell through the cracks last cycle"
* 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
fs: fix indentation in deactivate_super()
vfs: Remove duplicated d_mountpoint check in __is_local_mountpoint
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Merge tag 'ovl-update-5.8' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs
Pull overlayfs updates from Miklos Szeredi:
"Fixes:
- Resolve mount option conflicts consistently
- Sync before remount R/O
- Fix file handle encoding corner cases
- Fix metacopy related issues
- Fix an unintialized return value
- Add missing permission checks for underlying layers
Optimizations:
- Allow multipe whiteouts to share an inode
- Optimize small writes by inheriting SB_NOSEC from upper layer
- Do not call ->syncfs() multiple times for sync(2)
- Do not cache negative lookups on upper layer
- Make private internal mounts longterm"
* tag 'ovl-update-5.8' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs: (27 commits)
ovl: remove unnecessary lock check
ovl: make oip->index bool
ovl: only pass ->ki_flags to ovl_iocb_to_rwf()
ovl: make private mounts longterm
ovl: get rid of redundant members in struct ovl_fs
ovl: add accessor for ofs->upper_mnt
ovl: initialize error in ovl_copy_xattr
ovl: drop negative dentry in upper layer
ovl: check permission to open real file
ovl: call secutiry hook in ovl_real_ioctl()
ovl: verify permissions in ovl_path_open()
ovl: switch to mounter creds in readdir
ovl: pass correct flags for opening real directory
ovl: fix redirect traversal on metacopy dentries
ovl: initialize OVL_UPPERDATA in ovl_lookup()
ovl: use only uppermetacopy state in ovl_lookup()
ovl: simplify setting of origin for index lookup
ovl: fix out of bounds access warning in ovl_check_fb_len()
ovl: return required buffer size for file handles
ovl: sync dirty data when remounting to ro mode
...
Overlayfs is using clone_private_mount() to create internal mounts for
underlying layers. These are used for operations requiring a path, such as
dentry_open().
Since these private mounts are not in any namespace they are treated as
short term, "detached" mounts and mntput() involves taking the global
mount_lock, which can result in serious cacheline pingpong.
Make these private mounts longterm instead, which trade the penalty on
mntput() for a slightly longer shutdown time due to an added RCU grace
period when putting these mounts.
Introduce a new helper kern_unmount_many() that can take care of multiple
longterm mounts with a single RCU grace period.
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
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Merge tag 'threads-v5.8' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux
Pull thread updates from Christian Brauner:
"We have been discussing using pidfds to attach to namespaces for quite
a while and the patches have in one form or another already existed
for about a year. But I wanted to wait to see how the general api
would be received and adopted.
This contains the changes to make it possible to use pidfds to attach
to the namespaces of a process, i.e. they can be passed as the first
argument to the setns() syscall.
When only a single namespace type is specified the semantics are
equivalent to passing an nsfd. That means setns(nsfd, CLONE_NEWNET)
equals setns(pidfd, CLONE_NEWNET).
However, when a pidfd is passed, multiple namespace flags can be
specified in the second setns() argument and setns() will attach the
caller to all the specified namespaces all at once or to none of them.
Specifying 0 is not valid together with a pidfd. Here are just two
obvious examples:
setns(pidfd, CLONE_NEWPID | CLONE_NEWNS | CLONE_NEWNET);
setns(pidfd, CLONE_NEWUSER);
Allowing to also attach subsets of namespaces supports various
use-cases where callers setns to a subset of namespaces to retain
privilege, perform an action and then re-attach another subset of
namespaces.
Apart from significantly reducing the number of syscalls needed to
attach to all currently supported namespaces (eight "open+setns"
sequences vs just a single "setns()"), this also allows atomic setns
to a set of namespaces, i.e. either attaching to all namespaces
succeeds or we fail without having changed anything.
This is centered around a new internal struct nsset which holds all
information necessary for a task to switch to a new set of namespaces
atomically. Fwiw, with this change a pidfd becomes the only token
needed to interact with a container. I'm expecting this to be
picked-up by util-linux for nsenter rather soon.
Associated with this change is a shiny new test-suite dedicated to
setns() (for pidfds and nsfds alike)"
* tag 'threads-v5.8' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux:
selftests/pidfd: add pidfd setns tests
nsproxy: attach to namespaces via pidfds
nsproxy: add struct nsset
Pull vfs updates from Al Viro:
"Assorted patches from Miklos.
An interesting part here is /proc/mounts stuff..."
The "/proc/mounts stuff" is using a cursor for keeeping the location
data while traversing the mount listing.
Also probably worth noting is the addition of faccessat2(), which takes
an additional set of flags to specify how the lookup is done
(AT_EACCESS, AT_SYMLINK_NOFOLLOW, AT_EMPTY_PATH).
* 'from-miklos' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
vfs: add faccessat2 syscall
vfs: don't parse "silent" option
vfs: don't parse "posixacl" option
vfs: don't parse forbidden flags
statx: add mount_root
statx: add mount ID
statx: don't clear STATX_ATIME on SB_RDONLY
uapi: deprecate STATX_ALL
utimensat: AT_EMPTY_PATH support
vfs: split out access_override_creds()
proc/mounts: add cursor
aio: fix async fsync creds
vfs: allow unprivileged whiteout creation
This function acts as an out-of-line helper for is_local_mountpoint
is only called after the latter verifies the dentry is not a mountpoint.
There's no semantic changes and the resulting object code is smaller:
add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-26 (-26)
Function old new delta
__is_local_mountpoint 147 121 -26
Total: Before=34161, After=34135, chg -0.08%
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
If mounts are deleted after a read(2) call on /proc/self/mounts (or its
kin), the subsequent read(2) could miss a mount that comes after the
deleted one in the list. This is because the file position is interpreted
as the number mount entries from the start of the list.
E.g. first read gets entries #0 to #9; the seq file index will be 10. Then
entry #5 is deleted, resulting in #10 becoming #9 and #11 becoming #10,
etc... The next read will continue from entry #10, and #9 is missed.
Solve this by adding a cursor entry for each open instance. Taking the
global namespace_sem for write seems excessive, since we are only dealing
with a per-namespace list. Instead add a per-namespace spinlock and use
that together with namespace_sem taken for read to protect against
concurrent modification of the mount list. This may reduce parallelism of
is_local_mountpoint(), but it's hardly a big contention point. We could
also use RCU freeing of cursors to make traversal not need additional
locks, if that turns out to be neceesary.
Only move the cursor once for each read (cursor is not added on open) to
minimize cacheline invalidation. When EOF is reached, the cursor is taken
off the list, in order to prevent an excessive number of cursors due to
inactive open file descriptors.
Reported-by: Karel Zak <kzak@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
For quite a while we have been thinking about using pidfds to attach to
namespaces. This patchset has existed for about a year already but we've
wanted to wait to see how the general api would be received and adopted.
Now that more and more programs in userspace have started using pidfds
for process management it's time to send this one out.
This patch makes it possible to use pidfds to attach to the namespaces
of another process, i.e. they can be passed as the first argument to the
setns() syscall. When only a single namespace type is specified the
semantics are equivalent to passing an nsfd. That means
setns(nsfd, CLONE_NEWNET) equals setns(pidfd, CLONE_NEWNET). However,
when a pidfd is passed, multiple namespace flags can be specified in the
second setns() argument and setns() will attach the caller to all the
specified namespaces all at once or to none of them. Specifying 0 is not
valid together with a pidfd.
Here are just two obvious examples:
setns(pidfd, CLONE_NEWPID | CLONE_NEWNS | CLONE_NEWNET);
setns(pidfd, CLONE_NEWUSER);
Allowing to also attach subsets of namespaces supports various use-cases
where callers setns to a subset of namespaces to retain privilege, perform
an action and then re-attach another subset of namespaces.
If the need arises, as Eric suggested, we can extend this patchset to
assume even more context than just attaching all namespaces. His suggestion
specifically was about assuming the process' root directory when
setns(pidfd, 0) or setns(pidfd, SETNS_PIDFD) is specified. For now, just
keep it flexible in terms of supporting subsets of namespaces but let's
wait until we have users asking for even more context to be assumed. At
that point we can add an extension.
The obvious example where this is useful is a standard container
manager interacting with a running container: pushing and pulling files
or directories, injecting mounts, attaching/execing any kind of process,
managing network devices all these operations require attaching to all
or at least multiple namespaces at the same time. Given that nowadays
most containers are spawned with all namespaces enabled we're currently
looking at at least 14 syscalls, 7 to open the /proc/<pid>/ns/<ns>
nsfds, another 7 to actually perform the namespace switch. With time
namespaces we're looking at about 16 syscalls.
(We could amortize the first 7 or 8 syscalls for opening the nsfds by
stashing them in each container's monitor process but that would mean
we need to send around those file descriptors through unix sockets
everytime we want to interact with the container or keep on-disk
state. Even in scenarios where a caller wants to join a particular
namespace in a particular order callers still profit from batching
other namespaces. That mostly applies to the user namespace but
all container runtimes I found join the user namespace first no matter
if it privileges or deprivileges the container similar to how unshare
behaves.)
With pidfds this becomes a single syscall no matter how many namespaces
are supposed to be attached to.
A decently designed, large-scale container manager usually isn't the
parent of any of the containers it spawns so the containers don't die
when it crashes or needs to update or reinitialize. This means that
for the manager to interact with containers through pids is inherently
racy especially on systems where the maximum pid number is not
significicantly bumped. This is even more problematic since we often spawn
and manage thousands or ten-thousands of containers. Interacting with a
container through a pid thus can become risky quite quickly. Especially
since we allow for an administrator to enable advanced features such as
syscall interception where we're performing syscalls in lieu of the
container. In all of those cases we use pidfds if they are available and
we pass them around as stable references. Using them to setns() to the
target process' namespaces is as reliable as using nsfds. Either the
target process is already dead and we get ESRCH or we manage to attach
to its namespaces but we can't accidently attach to another process'
namespaces. So pidfds lend themselves to be used with this api.
The other main advantage is that with this change the pidfd becomes the
only relevant token for most container interactions and it's the only
token we need to create and send around.
Apart from significiantly reducing the number of syscalls from double
digit to single digit which is a decent reason post-spectre/meltdown
this also allows to switch to a set of namespaces atomically, i.e.
either attaching to all the specified namespaces succeeds or we fail. If
we fail we haven't changed a single namespace. There are currently three
namespaces that can fail (other than for ENOMEM which really is not
very interesting since we then have other problems anyway) for
non-trivial reasons, user, mount, and pid namespaces. We can fail to
attach to a pid namespace if it is not our current active pid namespace
or a descendant of it. We can fail to attach to a user namespace because
we are multi-threaded or because our current mount namespace shares
filesystem state with other tasks, or because we're trying to setns()
to the same user namespace, i.e. the target task has the same user
namespace as we do. We can fail to attach to a mount namespace because
it shares filesystem state with other tasks or because we fail to lookup
the new root for the new mount namespace. In most non-pathological
scenarios these issues can be somewhat mitigated. But there are cases where
we're half-attached to some namespace and failing to attach to another one.
I've talked about some of these problem during the hallway track (something
only the pre-COVID-19 generation will remember) of Plumbers in Los Angeles
in 2018(?). Even if all these issues could be avoided with super careful
userspace coding it would be nicer to have this done in-kernel. Pidfds seem
to lend themselves nicely for this.
The other neat thing about this is that setns() becomes an actual
counterpart to the namespace bits of unshare().
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Reviewed-by: Serge Hallyn <serge@hallyn.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Serge Hallyn <serge@hallyn.com>
Cc: Jann Horn <jannh@google.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Aleksa Sarai <cyphar@cyphar.com>
Link: https://lore.kernel.org/r/20200505140432.181565-3-christian.brauner@ubuntu.com
Add a simple struct nsset. It holds all necessary pieces to switch to a new
set of namespaces without leaving a task in a half-switched state which we
will make use of in the next patch. This patch switches the existing setns
logic over without causing a change in setns() behavior. This brings
setns() closer to how unshare() works(). The prepare_ns() function is
responsible to prepare all necessary information. This has two reasons.
First it minimizes dependencies between individual namespaces, i.e. all
install handler can expect that all fields are properly initialized
independent in what order they are called in. Second, this makes the code
easier to maintain and easier to follow if it needs to be changed.
The prepare_ns() helper will only be switched over to use a flags argument
in the next patch. Here it will still use nstype as a simple integer
argument which was argued would be clearer. I'm not particularly
opinionated about this if it really helps or not. The struct nsset itself
already contains the flags field since its name already indicates that it
can contain information required by different namespaces. None of this
should have functional consequences.
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Reviewed-by: Serge Hallyn <serge@hallyn.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Serge Hallyn <serge@hallyn.com>
Cc: Jann Horn <jannh@google.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Aleksa Sarai <cyphar@cyphar.com>
Link: https://lore.kernel.org/r/20200505140432.181565-2-christian.brauner@ubuntu.com
New LOOKUP flag, telling path_lookupat() to act as path_mountpointat().
IOW, traverse mounts at the final point and skip revalidation of the
location where it ends up.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
1) no instances of ->d_automount() have ever made use of the "return
ERR_PTR(-EISDIR) if you don't feel like mounting anything" - that's
a rudiment of plans that got superseded before the thing went into
the tree. Despite the comment in follow_automount(), autofs has
never done that.
2) if there's no ->d_automount() in dentry_operations, filesystems
should not set DCACHE_NEED_AUTOMOUNT in the first place. None have
ever done so...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Protection against automount/automount races (two threads hitting the same
referral point at the same time) is based upon do_add_mount() prevention of
identical overmounts - trying to overmount the root of mounted tree with
the same tree fails with -EBUSY. It's unreliable (the other thread might've
mounted something on top of the automount it has triggered) *and* causes
no end of headache for follow_automount() and its caller, since
finish_automount() behaves like do_new_mount() - if the mountpoint to be is
overmounted, it mounts on top what's overmounting it. It's not only wrong
(we want to go into what's overmounting the automount point and quietly
discard what we planned to mount there), it introduces the possibility of
original parent mount getting dropped. That's what 8aef188452 (VFS: Fix
vfsmount overput on simultaneous automount) deals with, but it can't do
anything about the reliability of conflict detection - if something had
been overmounted the other thread's automount (e.g. that other thread
having stepped into automount in mount(2)), we don't get that -EBUSY and
the result is
referral point under automounted NFS under explicit overmount
under another copy of automounted NFS
What we need is finish_automount() *NOT* digging into overmounts - if it
finds one, it should just quietly discard the thing it was asked to mount.
And don't bother with actually crossing into the results of finish_automount() -
the same loop that calls follow_automount() will do that just fine on the
next iteration.
IOW, instead of calling lock_mount() have finish_automount() do it manually,
_without_ the "move into overmount and retry" part. And leave crossing into
the results to the caller of follow_automount(), which simplifies it a lot.
Moral: if you end up with a lot of glue working around the calling conventions
of something, perhaps these calling conventions are simply wrong...
Fixes: 8aef188452 (VFS: Fix vfsmount overput on simultaneous automount)
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Make to_mnt_ns() static to address the following 'sparse' warning:
fs/namespace.c:1731:22: warning: symbol 'to_mnt_ns' was not declared. Should it be static?
Link: http://lkml.kernel.org/r/20191209234830.156260-1-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
In prepare_namespace(), do_mount() can be used instead of ksys_mount()
as the first and third argument are const strings in the kernel, the
second and fourth argument are passed through anyway, and the fifth
argument is NULL.
In do_mount_root(), ksys_mount() is called with the first and third
argument being already kernelspace strings, which do not need to be
copied over from userspace to kernelspace (again). The second and
fourth arguments are passed through to do_mount() anyway. The fifth
argument, while already residing in kernelspace, needs to be put into
a page of its own. Then, do_mount() can be used instead of
ksys_mount().
Once this is done, there are no in-kernel users to ksys_mount() left,
which can therefore be removed.
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
Pull misc vfs cleanups from Al Viro:
"No common topic, just three cleanups".
* 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
make __d_alloc() static
fs/namespace: add __user to open_tree and move_mount syscalls
fs/fnctl: fix missing __user in fcntl_rw_hint()
Thw open_tree and move_mount syscalls take names from the
user, so add the __user to these to ensure the following
warnings from sparse are fixed:
fs/namespace.c:2392:35: warning: incorrect type in argument 2 (different address spaces)
fs/namespace.c:2392:35: expected char const [noderef] <asn:1> *name
fs/namespace.c:2392:35: got char const *filename
fs/namespace.c:3541:38: warning: incorrect type in argument 2 (different address spaces)
fs/namespace.c:3541:38: expected char const [noderef] <asn:1> *name
fs/namespace.c:3541:38: got char const *from_pathname
fs/namespace.c:3550:36: warning: incorrect type in argument 2 (different address spaces)
fs/namespace.c:3550:36: expected char const [noderef] <asn:1> *name
fs/namespace.c:3550:36: got char const *to_pathname
Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
After do_add_mount() returns success, the caller doesn't hold a
reference to the 'struct mount' anymore. So it's invalid to access it
in mnt_warn_timestamp_expiry().
Fix it by calling mnt_warn_timestamp_expiry() before do_add_mount()
rather than after, and adjusting the warning message accordingly.
Reported-by: syzbot+da4f525235510683d855@syzkaller.appspotmail.com
Fixes: f8b92ba67c ("mount: Add mount warning for impending timestamp expiry")
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Merge more updates from Andrew Morton:
- almost all of the rest of -mm
- various other subsystems
Subsystems affected by this patch series:
memcg, misc, core-kernel, lib, checkpatch, reiserfs, fat, fork,
cpumask, kexec, uaccess, kconfig, kgdb, bug, ipc, lzo, kasan, madvise,
cleanups, pagemap
* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (77 commits)
arch/sparc/include/asm/pgtable_64.h: fix build
mm: treewide: clarify pgtable_page_{ctor,dtor}() naming
ntfs: remove (un)?likely() from IS_ERR() conditions
IB/hfi1: remove unlikely() from IS_ERR*() condition
xfs: remove unlikely() from WARN_ON() condition
wimax/i2400m: remove unlikely() from WARN*() condition
fs: remove unlikely() from WARN_ON() condition
xen/events: remove unlikely() from WARN() condition
checkpatch: check for nested (un)?likely() calls
hexagon: drop empty and unused free_initrd_mem
mm: factor out common parts between MADV_COLD and MADV_PAGEOUT
mm: introduce MADV_PAGEOUT
mm: change PAGEREF_RECLAIM_CLEAN with PAGE_REFRECLAIM
mm: introduce MADV_COLD
mm: untag user pointers in mmap/munmap/mremap/brk
vfio/type1: untag user pointers in vaddr_get_pfn
tee/shm: untag user pointers in tee_shm_register
media/v4l2-core: untag user pointers in videobuf_dma_contig_user_get
drm/radeon: untag user pointers in radeon_gem_userptr_ioctl
drm/amdgpu: untag user pointers
...
This patch is a part of a series that extends kernel ABI to allow to pass
tagged user pointers (with the top byte set to something else other than
0x00) as syscall arguments.
In copy_mount_options a user address is being subtracted from TASK_SIZE.
If the address is lower than TASK_SIZE, the size is calculated to not
allow the exact_copy_from_user() call to cross TASK_SIZE boundary.
However if the address is tagged, then the size will be calculated
incorrectly.
Untag the address before subtracting.
Link: http://lkml.kernel.org/r/1de225e4a54204bfd7f25dac2635e31aa4aa1d90.1563904656.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Khalid Aziz <khalid.aziz@oracle.com>
Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Eric Auger <eric.auger@redhat.com>
Cc: Felix Kuehling <Felix.Kuehling@amd.com>
Cc: Jens Wiklander <jens.wiklander@linaro.org>
Cc: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Merge tag 'fuse-update-5.4' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse
Pull fuse updates from Miklos Szeredi:
- Continue separating the transport (user/kernel communication) and the
filesystem layers of fuse. Getting rid of most layering violations
will allow for easier cleanup and optimization later on.
- Prepare for the addition of the virtio-fs filesystem. The actual
filesystem will be introduced by a separate pull request.
- Convert to new mount API.
- Various fixes, optimizations and cleanups.
* tag 'fuse-update-5.4' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse: (55 commits)
fuse: Make fuse_args_to_req static
fuse: fix memleak in cuse_channel_open
fuse: fix beyond-end-of-page access in fuse_parse_cache()
fuse: unexport fuse_put_request
fuse: kmemcg account fs data
fuse: on 64-bit store time in d_fsdata directly
fuse: fix missing unlock_page in fuse_writepage()
fuse: reserve byteswapped init opcodes
fuse: allow skipping control interface and forced unmount
fuse: dissociate DESTROY from fuseblk
fuse: delete dentry if timeout is zero
fuse: separate fuse device allocation and installation in fuse_conn
fuse: add fuse_iqueue_ops callbacks
fuse: extract fuse_fill_super_common()
fuse: export fuse_dequeue_forget() function
fuse: export fuse_get_unique()
fuse: export fuse_send_init_request()
fuse: export fuse_len_args()
fuse: export fuse_end_request()
fuse: fix request limit
...
This series from Deepa Dinamani adds a per-superblock minimum/maximum
timestamp limit for a file system, and clamps timestamps as they are
written, to avoid random behavior from integer overflow as well as having
different time stamps on disk vs in memory.
At mount time, a warning is now printed for any file system that can
represent current timestamps but not future timestamps more than 30
years into the future, similar to the arbitrary 30 year limit that was
added to settimeofday().
This was picked as a compromise to warn users to migrate to other file
systems (e.g. ext4 instead of ext3) when they need the file system to
survive beyond 2038 (or similar limits in other file systems), but not
get in the way of normal usage.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
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Merge tag 'y2038-vfs' of git://git.kernel.org/pub/scm/linux/kernel/git/arnd/playground
Pull y2038 vfs updates from Arnd Bergmann:
"Add inode timestamp clamping.
This series from Deepa Dinamani adds a per-superblock minimum/maximum
timestamp limit for a file system, and clamps timestamps as they are
written, to avoid random behavior from integer overflow as well as
having different time stamps on disk vs in memory.
At mount time, a warning is now printed for any file system that can
represent current timestamps but not future timestamps more than 30
years into the future, similar to the arbitrary 30 year limit that was
added to settimeofday().
This was picked as a compromise to warn users to migrate to other file
systems (e.g. ext4 instead of ext3) when they need the file system to
survive beyond 2038 (or similar limits in other file systems), but not
get in the way of normal usage"
* tag 'y2038-vfs' of git://git.kernel.org/pub/scm/linux/kernel/git/arnd/playground:
ext4: Reduce ext4 timestamp warnings
isofs: Initialize filesystem timestamp ranges
pstore: fs superblock limits
fs: omfs: Initialize filesystem timestamp ranges
fs: hpfs: Initialize filesystem timestamp ranges
fs: ceph: Initialize filesystem timestamp ranges
fs: sysv: Initialize filesystem timestamp ranges
fs: affs: Initialize filesystem timestamp ranges
fs: fat: Initialize filesystem timestamp ranges
fs: cifs: Initialize filesystem timestamp ranges
fs: nfs: Initialize filesystem timestamp ranges
ext4: Initialize timestamps limits
9p: Fill min and max timestamps in sb
fs: Fill in max and min timestamps in superblock
utimes: Clamp the timestamps before update
mount: Add mount warning for impending timestamp expiry
timestamp_truncate: Replace users of timespec64_trunc
vfs: Add timestamp_truncate() api
vfs: Add file timestamp range support
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Merge tag 'filelock-v5.4-1' of git://git.kernel.org/pub/scm/linux/kernel/git/jlayton/linux
Pull file locking updates from Jeff Layton:
"Just a couple of minor bugfixes, a revision to a tracepoint to account
for some earlier changes to the internals, and a patch to add a
pr_warn message when someone tries to mount a filesystem with '-o
mand' on a kernel that has that support disabled"
* tag 'filelock-v5.4-1' of git://git.kernel.org/pub/scm/linux/kernel/git/jlayton/linux:
locks: fix a memory leak bug in __break_lease()
locks: print a warning when mount fails due to lack of "mand" support
locks: Fix procfs output for file leases
locks: revise generic_add_lease tracepoint
Pull vfs namei updates from Al Viro:
"Pathwalk-related stuff"
[ Audit-related cleanups, misc simplifications, and easier to follow
nd->root refcounts - Linus ]
* 'work.namei' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
devpts_pty_kill(): don't bother with d_delete()
infiniband: don't bother with d_delete()
hypfs: don't bother with d_delete()
fs/namei.c: keep track of nd->root refcount status
fs/namei.c: new helper - legitimize_root()
kill the last users of user_{path,lpath,path_dir}()
namei.h: get the comments on LOOKUP_... in sync with reality
kill LOOKUP_NO_EVAL, don't bother including namei.h from audit.h
audit_inode(): switch to passing AUDIT_INODE_...
filename_mountpoint(): make LOOKUP_NO_EVAL unconditional there
filename_lookup(): audit_inode() argument is always 0
The unused vfs code can be removed. Don't pass empty subtype (same as if
->parse callback isn't called).
The bits that are left involve determining whether it's permitted to split the
filesystem type string passed in to mount(2). Consequently, this means that we
cannot get rid of the FS_HAS_SUBTYPE flag unless we define that a type string
with a dot in it always indicates a subtype specification.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
The warning reuses the uptime max of 30 years used by
settimeofday().
Note that the warning is only emitted for writable filesystem mounts
through the mount syscall. Automounts do not have the same warning.
Print out the warning in human readable format using the struct tm.
After discussion with Arnd Bergmann, we chose to print only the year number.
The raw s_time_max is also displayed, and the user can easily decode
it e.g. "date -u -d @$((0x7fffffff))". We did not want to consolidate
struct rtc_tm and struct tm just to print the date using a format specifier
as part of this series.
Given that the rtc_tm is not compiled on all architectures, this is not a
trivial patch. This can be added in the future.
Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com>
Acked-by: Jeff Layton <jlayton@kernel.org>
Since 9e8925b67a ("locks: Allow disabling mandatory locking at compile
time"), attempts to mount filesystems with "-o mand" will fail.
Unfortunately, there is no other indiciation of the reason for the
failure.
Change how the function is defined for better readability. When
CONFIG_MANDATORY_FILE_LOCKING is disabled, printk a warning when
someone attempts to mount with -o mand.
Also, add a blurb to the mandatory-locking.txt file to explain about
the "mand" option, and the behavior one should expect when it is
disabled.
Reported-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
We need to drop everything we remove from the tree, whether
mnt_has_parent() is true or not. Usually the bug manifests as a slow
memory leak (leaked struct mount for initramfs); it becomes much more
visible in mount_subtree() users, such as btrfs. There we leak
a struct mount for btrfs superblock being mounted, which prevents
fs shutdown on subsequent umount.
Fixes: 56cbb429d9 ("switch the remnants of releasing the mountpoint away from fs_pin")
Reported-by: Nikolay Borisov <nborisov@suse.com>
Tested-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Al Viro
Linus Torvalds
Eric Biggers
Jens Axboe
Christoph Hellwig
Catalin Marinas
Mattias Nissler
Kirill Tkhai
Miklos Szeredi
Nikolay Borisov
Christian Brauner
Mauro Carvalho Chehab
Dominik Brodowski
Ben Dooks
Andrey Konovalov
David Howells
Deepa Dinamani
Jeff Layton