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Commits
| Author | SHA1 | Message | Date | |
|---|---|---|---|---|
 Linus Torvalds
|
7c8a4671dc |
Merge tag 'vfs-7.1-rc1.mount.v2' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
Pull vfs mount updates from Christian Brauner:
- Add FSMOUNT_NAMESPACE flag to fsmount() that creates a new mount
namespace with the newly created filesystem attached to a copy of the
real rootfs. This returns a namespace file descriptor instead of an
O_PATH mount fd, similar to how OPEN_TREE_NAMESPACE works for
open_tree().
This allows creating a new filesystem and immediately placing it in a
new mount namespace in a single operation, which is useful for
container runtimes and other namespace-based isolation mechanisms.
This accompanies OPEN_TREE_NAMESPACE and avoids a needless detour via
OPEN_TREE_NAMESPACE to get the same effect. Will be especially useful
when you mount an actual filesystem to be used as the container
rootfs.
- Currently, creating a new mount namespace always copies the entire
mount tree from the caller's namespace. For containers and sandboxes
that intend to build their mount table from scratch this is wasteful:
they inherit a potentially large mount tree only to immediately tear
it down.
This series adds support for creating a mount namespace that contains
only a clone of the root mount, with none of the child mounts. Two
new flags are introduced:
- CLONE_EMPTY_MNTNS (0x400000000) for clone3(), using the 64-bit flag space
- UNSHARE_EMPTY_MNTNS (0x00100000) for unshare()
Both flags imply CLONE_NEWNS. The resulting namespace contains a
single nullfs root mount with an immutable empty directory. The
intended workflow is to then mount a real filesystem (e.g., tmpfs)
over the root and build the mount table from there.
- Allow MOVE_MOUNT_BENEATH to target the caller's rootfs, allowing to
switch out the rootfs without pivot_root(2).
The traditional approach to switching the rootfs involves
pivot_root(2) or a chroot_fs_refs()-based mechanism that atomically
updates fs->root for all tasks sharing the same fs_struct. This has
consequences for fork(), unshare(CLONE_FS), and setns().
This series instead decomposes root-switching into individually
atomic, locally-scoped steps:
fd_tree = open_tree(-EBADF, "/newroot", OPEN_TREE_CLONE | OPEN_TREE_CLOEXEC);
fchdir(fd_tree);
move_mount(fd_tree, "", AT_FDCWD, "/", MOVE_MOUNT_BENEATH | MOVE_MOUNT_F_EMPTY_PATH);
chroot(".");
umount2(".", MNT_DETACH);
Since each step only modifies the caller's own state, the
fork/unshare/setns races are eliminated by design.
A key step to making this possible is to remove the locked mount
restriction. Originally MOVE_MOUNT_BENEATH doesn't support mounting
beneath a mount that is locked. The locked mount protects the
underlying mount from being revealed. This is a core mechanism of
unshare(CLONE_NEWUSER | CLONE_NEWNS). The mounts in the new mount
namespace become locked. That effectively makes the new mount table
useless as the caller cannot ever get rid of any of the mounts no
matter how useless they are.
We can lift this restriction though. We simply transfer the locked
property from the top mount to the mount beneath. This works because
what we care about is to protect the underlying mount aka the parent.
The mount mounted between the parent and the top mount takes over the
job of protecting the parent mount from the top mount mount. This
leaves us free to remove the locked property from the top mount which
can consequently be unmounted:
unshare(CLONE_NEWUSER | CLONE_NEWNS)
and we inherit a clone of procfs on /proc then currently we cannot
unmount it as:
umount -l /proc
will fail with EINVAL because the procfs mount is locked.
After this series we can now do:
mount --beneath -t tmpfs tmpfs /proc
umount -l /proc
after which a tmpfs mount has been placed beneath the procfs mount.
The tmpfs mount has become locked and the procfs mount has become
unlocked.
This means you can safely modify an inherited mount table after
unprivileged namespace creation.
Afterwards we simply make it possible to move a mount beneath the
rootfs allowing to upgrade the rootfs.
Removing the locked restriction makes this very useful for containers
created with unshare(CLONE_NEWUSER | CLONE_NEWNS) to reshuffle an
inherited mount table safely and MOVE_MOUNT_BENEATH makes it possible
to switch out the rootfs instead of using the costly pivot_root(2).
* tag 'vfs-7.1-rc1.mount.v2' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
selftests/namespaces: remove unused utils.h include from listns_efault_test
selftests/fsmount_ns: add missing TARGETS and fix cap test
selftests/empty_mntns: fix wrong CLONE_EMPTY_MNTNS hex value in comment
selftests/empty_mntns: fix statmount_alloc() signature mismatch
selftests/statmount: remove duplicate wait_for_pid()
mount: always duplicate mount
selftests/filesystems: add MOVE_MOUNT_BENEATH rootfs tests
move_mount: allow MOVE_MOUNT_BENEATH on the rootfs
move_mount: transfer MNT_LOCKED
selftests/filesystems: add clone3 tests for empty mount namespaces
selftests/filesystems: add tests for empty mount namespaces
namespace: allow creating empty mount namespaces
selftests: add FSMOUNT_NAMESPACE tests
selftests/statmount: add statmount_alloc() helper
tools: update mount.h header
mount: add FSMOUNT_NAMESPACE
mount: simplify __do_loopback()
mount: start iterating from start of rbtree
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  Mickaël SalaünandChristian Brauner
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935a04923a |
nsproxy: Add FOR_EACH_NS_TYPE() X-macro and CLONE_NS_ALL
Introduce the FOR_EACH_NS_TYPE(X) macro as the single source of truth for the set of (struct type, CLONE_NEW* flag) pairs that define Linux namespace types. Currently, the list of CLONE_NEW* flags is duplicated inline in multiple call sites and would need another copy in each new consumer. This makes it easy to miss one when a new namespace type is added. Derive two things from the X-macro: - CLONE_NS_ALL: Bitmask of all known CLONE_NEW* flags, usable as a validity mask or iteration bound. - ns_common_type(): Rewritten to use the X-macro via a leading-comma _Generic pattern, so the struct-to-flag mapping stays in sync with the flag set automatically. Replace the inline flag enumerations in copy_namespaces(), unshare_nsproxy_namespaces(), check_setns_flags(), and ksys_unshare() with CLONE_NS_ALL. When a new namespace type is added, only FOR_EACH_NS_TYPE needs to be updated; CLONE_NS_ALL, ns_common_type(), and all the call sites pick up the change automatically. Cc: Christian Brauner <brauner@kernel.org> Cc: Günther Noack <gnoack@google.com> Signed-off-by: Mickaël Salaün <mic@digikod.net> Link: https://patch.msgid.link/20260312100444.2609563-4-mic@digikod.net Reviewed-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Christian Brauner <brauner@kernel.org> |
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Christian Brauner
|
9d4e752a24 |
namespace: allow creating empty mount namespaces
Add support for creating a mount namespace that contains only a copy of the root mount from the caller's mount namespace, with none of the child mounts. This is useful for containers and sandboxes that want to start with a minimal mount table and populate it from scratch rather than inheriting and then tearing down the full mount tree. Two new flags are introduced: - CLONE_EMPTY_MNTNS for clone3(), using the 64-bit flag space. - UNSHARE_EMPTY_MNTNS for unshare(), reusing the CLONE_PARENT_SETTID bit which has no meaning for unshare. Both flags imply CLONE_NEWNS. For the unshare path, UNSHARE_EMPTY_MNTNS is converted to CLONE_EMPTY_MNTNS in unshare_nsproxy_namespaces() before it reaches copy_mnt_ns(), so the mount namespace code only needs to handle a single flag. In copy_mnt_ns(), when CLONE_EMPTY_MNTNS is set, clone_mnt() is used instead of copy_tree() to clone only the root mount. The caller's root and working directory are both reset to the root dentry of the new mount. The cleanup variables are changed from vfsmount pointers with __free(mntput) to struct path with __free(path_put) because the empty mount namespace path needs to release both mount and dentry references when replacing the caller's root and pwd. In the normal (non-empty) path only the mount component is set, and dput(NULL) is a no-op so path_put remains correct there as well. Link: https://patch.msgid.link/20260306-work-empty-mntns-consolidated-v1-1-6eb30529bbb0@kernel.org Signed-off-by: Christian Brauner <brauner@kernel.org> |
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Christian Brauner
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cefd55bd21 |
nsproxy: fix free_nsproxy() and simplify create_new_namespaces()
Make it possible to handle NULL being passed to the reference count helpers instead of forcing the caller to handle this. Afterwards we can nicely allow a cleanup guard to handle nsproxy freeing. Active reference count handling is not done in nsproxy_free() but rather in free_nsproxy() as nsproxy_free() is also called from setns() failure paths where a new nsproxy has been prepared but has not been marked as active via switch_task_namespaces(). Link: https://lore.kernel.org/690bfb9e.050a0220.2e3c35.0013.GAE@google.com Link: https://patch.msgid.link/20251111-sakralbau-guthaben-7dcc277d337f@brauner Fixes: 3c9820d5c64a ("ns: add active reference count") Reported-by: syzbot+0b2e79f91ff6579bfa5b@syzkaller.appspotmail.com Reported-by: syzbot+0a8655a80e189278487e@syzkaller.appspotmail.com Signed-off-by: Christian Brauner <brauner@kernel.org> |
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Christian Brauner
|
3a18f80918 |
ns: add active reference count
The namespace tree is, among other things, currently used to support
file handles for namespaces. When a namespace is created it is placed on
the namespace trees and when it is destroyed it is removed from the
namespace trees.
While a namespace is on the namespace trees with a valid reference count
it is possible to reopen it through a namespace file handle. This is all
fine but has some issues that should be addressed.
On current kernels a namespace is visible to userspace in the
following cases:
(1) The namespace is in use by a task.
(2) The namespace is persisted through a VFS object (namespace file
descriptor or bind-mount).
Note that (2) only cares about direct persistence of the namespace
itself not indirectly via e.g., file->f_cred file references or
similar.
(3) The namespace is a hierarchical namespace type and is the parent of
a single or multiple child namespaces.
Case (3) is interesting because it is possible that a parent namespace
might not fulfill any of (1) or (2), i.e., is invisible to userspace but
it may still be resurrected through the NS_GET_PARENT ioctl().
Currently namespace file handles allow much broader access to namespaces
than what is currently possible via (1)-(3). The reason is that
namespaces may remain pinned for completely internal reasons yet are
inaccessible to userspace.
For example, a user namespace my remain pinned by get_cred() calls to
stash the opener's credentials into file->f_cred. As it stands file
handles allow to resurrect such a users namespace even though this
should not be possible via (1)-(3). This is a fundamental uapi change
that we shouldn't do if we don't have to.
Consider the following insane case: Various architectures support the
CONFIG_MMU_LAZY_TLB_REFCOUNT option which uses lazy TLB destruction.
When this option is set a userspace task's struct mm_struct may be used
for kernel threads such as the idle task and will only be destroyed once
the cpu's runqueue switches back to another task. But because of ptrace()
permission checks struct mm_struct stashes the user namespace of the
task that struct mm_struct originally belonged to. The kernel thread
will take a reference on the struct mm_struct and thus pin it.
So on an idle system user namespaces can be persisted for arbitrary
amounts of time which also means that they can be resurrected using
namespace file handles. That makes no sense whatsoever. The problem is
of course excarabted on large systems with a huge number of cpus.
To handle this nicely we introduce an active reference count which
tracks (1)-(3). This is easy to do as all of these things are already
managed centrally. Only (1)-(3) will count towards the active reference
count and only namespaces which are active may be opened via namespace
file handles.
The problem is that namespaces may be resurrected. Which means that they
can become temporarily inactive and will be reactived some time later.
Currently the only example of this is the SIOGCSKNS socket ioctl. The
SIOCGSKNS ioctl allows to open a network namespace file descriptor based
on a socket file descriptor.
If a socket is tied to a network namespace that subsequently becomes
inactive but that socket is persisted by another process in another
network namespace (e.g., via SCM_RIGHTS of pidfd_getfd()) then the
SIOCGSKNS ioctl will resurrect this network namespace.
So calls to open_related_ns() and open_namespace() will end up
resurrecting the corresponding namespace tree.
Note that the active reference count does not regulate the lifetime of
the namespace itself. This is still done by the normal reference count.
The active reference count can only be elevated if the regular reference
count is elevated.
The active reference count also doesn't regulate the presence of a
namespace on the namespace trees. It only regulates its visiblity to
namespace file handles (and in later patches to listns()).
A namespace remains on the namespace trees from creation until its
actual destruction. This will allow the kernel to always reach any
namespace trivially and it will also enable subsystems like bpf to walk
the namespace lists on the system for tracing or general introspection
purposes.
Note that different namespaces have different visibility lifetimes on
current kernels. While most namespace are immediately released when the
last task using them exits, the user- and pid namespace are persisted
and thus both remain accessible via /proc/<pid>/ns/<ns_type>.
The user namespace lifetime is aliged with struct cred and is only
released through exit_creds(). However, it becomes inaccessible to
userspace once the last task using it is reaped, i.e., when
release_task() is called and all proc entries are flushed. Similarly,
the pid namespace is also visible until the last task using it has been
reaped and the associated pid numbers are freed.
The active reference counts of the user- and pid namespace are
decremented once the task is reaped.
Link: https://patch.msgid.link/20251029-work-namespace-nstree-listns-v4-11-2e6f823ebdc0@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Christian Brauner
|
4b06b70c82 |
ns: rename to exit_nsproxy_namespaces()
The current naming is very misleading as this really isn't exiting all of the task's namespaces. It is only exiting the namespaces that hang of off nsproxy. Reflect that in the name. Link: https://patch.msgid.link/20251029-work-namespace-nstree-listns-v4-10-2e6f823ebdc0@kernel.org Reviewed-by: Jeff Layton <jlayton@kernel.org> Signed-off-by: Christian Brauner <brauner@kernel.org> |
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Linus Torvalds
|
18b19abc37 |
Merge tag 'namespace-6.18-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
Pull namespace updates from Christian Brauner: "This contains a larger set of changes around the generic namespace infrastructure of the kernel. Each specific namespace type (net, cgroup, mnt, ...) embedds a struct ns_common which carries the reference count of the namespace and so on. We open-coded and cargo-culted so many quirks for each namespace type that it just wasn't scalable anymore. So given there's a bunch of new changes coming in that area I've started cleaning all of this up. The core change is to make it possible to correctly initialize every namespace uniformly and derive the correct initialization settings from the type of the namespace such as namespace operations, namespace type and so on. This leaves the new ns_common_init() function with a single parameter which is the specific namespace type which derives the correct parameters statically. This also means the compiler will yell as soon as someone does something remotely fishy. The ns_common_init() addition also allows us to remove ns_alloc_inum() and drops any special-casing of the initial network namespace in the network namespace initialization code that Linus complained about. Another part is reworking the reference counting. The reference counting was open-coded and copy-pasted for each namespace type even though they all followed the same rules. This also removes all open accesses to the reference count and makes it private and only uses a very small set of dedicated helpers to manipulate them just like we do for e.g., files. In addition this generalizes the mount namespace iteration infrastructure introduced a few cycles ago. As reminder, the vfs makes it possible to iterate sequentially and bidirectionally through all mount namespaces on the system or all mount namespaces that the caller holds privilege over. This allow userspace to iterate over all mounts in all mount namespaces using the listmount() and statmount() system call. Each mount namespace has a unique identifier for the lifetime of the systems that is exposed to userspace. The network namespace also has a unique identifier working exactly the same way. This extends the concept to all other namespace types. The new nstree type makes it possible to lookup namespaces purely by their identifier and to walk the namespace list sequentially and bidirectionally for all namespace types, allowing userspace to iterate through all namespaces. Looking up namespaces in the namespace tree works completely locklessly. This also means we can move the mount namespace onto the generic infrastructure and remove a bunch of code and members from struct mnt_namespace itself. There's a bunch of stuff coming on top of this in the future but for now this uses the generic namespace tree to extend a concept introduced first for pidfs a few cycles ago. For a while now we have supported pidfs file handles for pidfds. This has proven to be very useful. This extends the concept to cover namespaces as well. It is possible to encode and decode namespace file handles using the common name_to_handle_at() and open_by_handle_at() apis. As with pidfs file handles, namespace file handles are exhaustive, meaning it is not required to actually hold a reference to nsfs in able to decode aka open_by_handle_at() a namespace file handle. Instead the FD_NSFS_ROOT constant can be passed which will let the kernel grab a reference to the root of nsfs internally and thus decode the file handle. Namespaces file descriptors can already be derived from pidfds which means they aren't subject to overmount protection bugs. IOW, it's irrelevant if the caller would not have access to an appropriate /proc/<pid>/ns/ directory as they could always just derive the namespace based on a pidfd already. It has the same advantage as pidfds. It's possible to reliably and for the lifetime of the system refer to a namespace without pinning any resources and to compare them trivially. Permission checking is kept simple. If the caller is located in the namespace the file handle refers to they are able to open it otherwise they must hold privilege over the owning namespace of the relevant namespace. The namespace file handle layout is exposed as uapi and has a stable and extensible format. For now it simply contains the namespace identifier, the namespace type, and the inode number. The stable format means that userspace may construct its own namespace file handles without going through name_to_handle_at() as they are already allowed for pidfs and cgroup file handles" * tag 'namespace-6.18-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (65 commits) ns: drop assert ns: move ns type into struct ns_common nstree: make struct ns_tree private ns: add ns_debug() ns: simplify ns_common_init() further cgroup: add missing ns_common include ns: use inode initializer for initial namespaces selftests/namespaces: verify initial namespace inode numbers ns: rename to __ns_ref nsfs: port to ns_ref_*() helpers net: port to ns_ref_*() helpers uts: port to ns_ref_*() helpers ipv4: use check_net() net: use check_net() net-sysfs: use check_net() user: port to ns_ref_*() helpers time: port to ns_ref_*() helpers pid: port to ns_ref_*() helpers ipc: port to ns_ref_*() helpers cgroup: port to ns_ref_*() helpers ... |
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Christian Brauner
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4055526d35 |
ns: move ns type into struct ns_common
It's misplaced in struct proc_ns_operations and ns->ops might be NULL if the namespace is compiled out but we still want to know the type of the namespace for the initial namespace struct. Reviewed-by: Jan Kara <jack@suse.cz> Signed-off-by: Christian Brauner <brauner@kernel.org> |
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 Simon SchusterandChristian Brauner
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edd3cb05c0 |
copy_process: pass clone_flags as u64 across calltree
With the introduction of clone3 in commit
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 Joel SavitzandChristian Brauner
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5caa2d89b7 |
kernel/nsproxy: remove unnecessary guards
In free_nsproxy() and the error path of create_new_namesapces() the put_*_ns() calls are guarded by unnecessary NULL checks. put_pid_ns(), put_ipc_ns(), put_uts_ns(), and put_time_ns() will never receive a NULL argument unless their namespace type is disabled, and in this case all four become no-ops at compile time anyway. put_mnt_ns() will never receive a null argument at any time. This unguarded usage is in line with other call sites of put_*_ns(). Signed-off-by: Joel Savitz <jsavitz@redhat.com> Link: https://lore.kernel.org/20250508184930.183040-2-jsavitz@redhat.com Signed-off-by: Christian Brauner <brauner@kernel.org> |
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 Al Viro
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6348be02ee |
fdget(), trivial conversions
fdget() is the first thing done in scope, all matching fdput() are immediately followed by leaving the scope. Reviewed-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> |
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Al Viro
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1da91ea87a |
introduce fd_file(), convert all accessors to it.
For any changes of struct fd representation we need to
turn existing accesses to fields into calls of wrappers.
Accesses to struct fd::flags are very few (3 in linux/file.h,
1 in net/socket.c, 3 in fs/overlayfs/file.c and 3 more in
explicit initializers).
Those can be dealt with in the commit converting to
new layout; accesses to struct fd::file are too many for that.
This commit converts (almost) all of f.file to
fd_file(f). It's not entirely mechanical ('file' is used as
a member name more than just in struct fd) and it does not
even attempt to distinguish the uses in pointer context from
those in boolean context; the latter will be eventually turned
into a separate helper (fd_empty()).
NOTE: mass conversion to fd_empty(), tempting as it
might be, is a bad idea; better do that piecewise in commit
that convert from fdget...() to CLASS(...).
[conflicts in fs/fhandle.c, kernel/bpf/syscall.c, mm/memcontrol.c
caught by git; fs/stat.c one got caught by git grep]
[fs/xattr.c conflict]
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Christian Brauner
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cb12fd8e0d |
pidfd: add pidfs
This moves pidfds from the anonymous inode infrastructure to a tiny pseudo filesystem. This has been on my todo for quite a while as it will unblock further work that we weren't able to do simply because of the very justified limitations of anonymous inodes. Moving pidfds to a tiny pseudo filesystem allows: * statx() on pidfds becomes useful for the first time. * pidfds can be compared simply via statx() and then comparing inode numbers. * pidfds have unique inode numbers for the system lifetime. * struct pid is now stashed in inode->i_private instead of file->private_data. This means it is now possible to introduce concepts that operate on a process once all file descriptors have been closed. A concrete example is kill-on-last-close. * file->private_data is freed up for per-file options for pidfds. * Each struct pid will refer to a different inode but the same struct pid will refer to the same inode if it's opened multiple times. In contrast to now where each struct pid refers to the same inode. Even if we were to move to anon_inode_create_getfile() which creates new inodes we'd still be associating the same struct pid with multiple different inodes. The tiny pseudo filesystem is not visible anywhere in userspace exactly like e.g., pipefs and sockfs. There's no lookup, there's no complex inode operations, nothing. Dentries and inodes are always deleted when the last pidfd is closed. We allocate a new inode for each struct pid and we reuse that inode for all pidfds. We use iget_locked() to find that inode again based on the inode number which isn't recycled. We allocate a new dentry for each pidfd that uses the same inode. That is similar to anonymous inodes which reuse the same inode for thousands of dentries. For pidfds we're talking way less than that. There usually won't be a lot of concurrent openers of the same struct pid. They can probably often be counted on two hands. I know that systemd does use separate pidfd for the same struct pid for various complex process tracking issues. So I think with that things actually become way simpler. Especially because we don't have to care about lookup. Dentries and inodes continue to be always deleted. The code is entirely optional and fairly small. If it's not selected we fallback to anonymous inodes. Heavily inspired by nsfs which uses a similar stashing mechanism just for namespaces. Link: https://lore.kernel.org/r/20240213-vfs-pidfd_fs-v1-2-f863f58cfce1@kernel.org Signed-off-by: Christian Brauner <brauner@kernel.org> |
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  Elena ReshetovaandKees Cook
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2ddd3cac1f |
nsproxy: Convert nsproxy.count to refcount_t
atomic_t variables are currently used to implement reference counters with the following properties: - counter is initialized to 1 using atomic_set() - a resource is freed upon counter reaching zero - once counter reaches zero, its further increments aren't allowed - counter schema uses basic atomic operations (set, inc, inc_not_zero, dec_and_test, etc.) Such atomic variables should be converted to a newly provided refcount_t type and API that prevents accidental counter overflows and underflows. This is important since overflows and underflows can lead to use-after-free situation and be exploitable. The variable nsproxy.count is used as pure reference counter. Convert it to refcount_t and fix up the operations. **Important note for maintainers: Some functions from refcount_t API defined in refcount.h have different memory ordering guarantees than their atomic counterparts. Please check Documentation/core-api/refcount-vs-atomic.rst for more information. Normally the differences should not matter since refcount_t provides enough guarantees to satisfy the refcounting use cases, but in some rare cases it might matter. Please double check that you don't have some undocumented memory guarantees for this variable usage. For the nsproxy.count it might make a difference in following places: - put_nsproxy() and switch_task_namespaces(): decrement in refcount_dec_and_test() only provides RELEASE ordering and ACQUIRE ordering on success vs. fully ordered atomic counterpart Suggested-by: Kees Cook <keescook@chromium.org> Signed-off-by: Elena Reshetova <elena.reshetova@intel.com> Reviewed-by: David Windsor <dwindsor@gmail.com> Reviewed-by: Hans Liljestrand <ishkamiel@gmail.com> Reviewed-by: Christian Brauner <brauner@kernel.org> Link: https://lore.kernel.org/r/20230818041327.gonna.210-kees@kernel.org Signed-off-by: Kees Cook <keescook@chromium.org> |
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Al Viro
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281117ccb2 |
convert setns(2) to fdget()/fdput()
Reviewed-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> |
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 Andrei VaginandKees Cook
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2b5f9dad32 |
fs/exec: switch timens when a task gets a new mm
Changing a time namespace requires remapping a vvar page, so we don't want
to allow doing that if any other tasks can use the same mm.
Currently, we install a time namespace when a task is created with a new
vm. exec() is another case when a task gets a new mm and so it can switch
a time namespace safely, but it isn't handled now.
One more issue of the current interface is that clone() with CLONE_VM isn't
allowed if the current task has unshared a time namespace
(timens_for_children doesn't match the current timens).
Both these issues make some inconvenience for users. For example, Alexey
and Florian reported that posix_spawn() uses vfork+exec and this pattern
doesn't work with time namespaces due to the both described issues.
LXC needed to workaround the exec() issue by calling setns.
In the commit
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Andrei VaginandKees Cook
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33a2d6bc34 |
Revert "fs/exec: allow to unshare a time namespace on vfork+exec"
This reverts commit
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Andrei VaginandKees Cook
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133e2d3e81 |
fs/exec: allow to unshare a time namespace on vfork+exec
Right now, a new process can't be forked in another time namespace if it shares mm with its parent. It is prohibited, because each time namespace has its own vvar page that is mapped into a process address space. When a process calls exec, it gets a new mm and so it could be "legal" to switch time namespace in that case. This was not implemented and now if we want to do this, we need to add another clone flag to not break backward compatibility. We don't have any user requests to switch times on exec except the vfork+exec combination, so there is no reason to add a new clone flag. As for vfork+exec, this should be safe to allow switching timens with the current clone flag. Right now, vfork (CLONE_VFORK | CLONE_VM) fails if a child is forked into another time namespace. With this change, vfork creates a new process in parent's timens, and the following exec does the actual switch to the target time namespace. Suggested-by: Florian Weimer <fweimer@redhat.com> Signed-off-by: Andrei Vagin <avagin@gmail.com> Acked-by: Christian Brauner (Microsoft) <brauner@kernel.org> Signed-off-by: Kees Cook <keescook@chromium.org> Link: https://lore.kernel.org/r/20220613060723.197407-1-avagin@gmail.com |
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 Vasily AverinandLinus Torvalds
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30acd0bdfb |
memcg: enable accounting for new namesapces and struct nsproxy
Container admin can create new namespaces and force kernel to allocate up to several pages of memory for the namespaces and its associated structures. Net and uts namespaces have enabled accounting for such allocations. It makes sense to account for rest ones to restrict the host's memory consumption from inside the memcg-limited container. Link: https://lkml.kernel.org/r/5525bcbf-533e-da27-79b7-158686c64e13@virtuozzo.com Signed-off-by: Vasily Averin <vvs@virtuozzo.com> Acked-by: Serge Hallyn <serge@hallyn.com> Acked-by: Christian Brauner <christian.brauner@ubuntu.com> Acked-by: Kirill Tkhai <ktkhai@virtuozzo.com> Reviewed-by: Shakeel Butt <shakeelb@google.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: Andrei Vagin <avagin@gmail.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Borislav Petkov <bp@suse.de> Cc: Dmitry Safonov <0x7f454c46@gmail.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: "J. Bruce Fields" <bfields@fieldses.org> Cc: Jeff Layton <jlayton@kernel.org> Cc: Jens Axboe <axboe@kernel.dk> Cc: Jiri Slaby <jirislaby@kernel.org> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Roman Gushchin <guro@fb.com> Cc: Tejun Heo <tj@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Cc: Yutian Yang <nglaive@gmail.com> Cc: Zefan Li <lizefan.x@bytedance.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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Linus Torvalds
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f9b4240b07 |
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
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  Hui SuandChristian Brauner
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aabe19b827 |
nsproxy: use put_nsproxy() in switch_task_namespaces()
We already have a dedicated helper that handles reference count checking so stop open-coding the reference count check in switch_task_namespaces() and use the dedicated put_nsproxy() helper instead. Take the change to fix a whitespace issue too. Signed-off-by: Hui Su <sh_def@163.com> [christian.brauner@ubuntu.com: expand commit message] Acked-by: Christian Brauner <christian.brauner@ubuntu.com> Link: https://lore.kernel.org/r/20201115180054.GA371317@rlk Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> |
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Hui SuandChristian Brauner
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5c62634fc6 |
namespace: make timens_on_fork() return nothing
timens_on_fork() always return 0, and maybe not need to judge the return value in copy_namespaces(). So make timens_on_fork() return nothing and do not judge its return val in copy_namespaces(). Signed-off-by: Hui Su <sh_def@163.com> Link: https://lore.kernel.org/r/20201117161750.GA45121@rlk Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> |
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Christian Brauner
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76c12881a3 |
nsproxy: support CLONE_NEWTIME with setns()
So far setns() was missing time namespace support. This was partially due to it simply not being implemented but also because vdso_join_timens() could still fail which made switching to multiple namespaces atomically problematic. This is now fixed so support CLONE_NEWTIME with setns() Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> Reviewed-by: Andrei Vagin <avagin@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Michael Kerrisk <mtk.manpages@gmail.com> Cc: Serge Hallyn <serge@hallyn.com> Cc: Dmitry Safonov <dima@arista.com> Link: https://lore.kernel.org/r/20200706154912.3248030-4-christian.brauner@ubuntu.com |
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Christian Brauner
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e571d4ee33 |
nsproxy: restore EINVAL for non-namespace file descriptor
The LTP testsuite reported a regression where users would now see EBADF
returned instead of EINVAL when an fd was passed that referred to an open
file but the file was not a nsfd. Fix this by continuing to report EINVAL.
Reported-by: kernel test robot <rong.a.chen@intel.com>
Cc: Jan Stancek <jstancek@redhat.com>
Cc: Cyril Hrubis <chrubis@suse.cz>
Link: https://lore.kernel.org/lkml/20200615085836.GR12456@shao2-debian
Fixes:
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Christian Brauner
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303cc571d1 |
nsproxy: attach to namespaces via pidfds
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 |