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  1. 13 May, 2020 2 commits
    • Christian Brauner's avatar
      selftests/pidfd: add pidfd setns tests · 2b40c5db
      Christian Brauner authored 
      This is basically a test-suite for setns() and as of now contains:
- test that we can't pass garbage flags
- test that we can't attach to the namespaces of  task that has already exited
- test that we can incrementally setns into all namespaces of a target task
  using a pidfd
- test that we can setns atomically into all namespaces of a target task
- test that we can't cross setns into a user namespace outside of our user
  namespace hierarchy
- test that we can't setns into namespaces owned by user namespaces over which
  we are not privileged
Signed-off-by: default avatarChristian Brauner <christian.brauner@ubuntu.com>
Link: https://lore.kernel.org/r/20200505140432.181565-4-christian.brauner@ubuntu.com
      2b40c5db
    • Christian Brauner's avatar
      nsproxy: attach to namespaces via pidfds · 303cc571
      Christian Brauner authored 
      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: default avatarChristian Brauner <christian.brauner@ubuntu.com>
Reviewed-by: default avatarSerge 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
      303cc571
  3. 09 May, 2020 1 commit
    • Christian Brauner's avatar
      nsproxy: add struct nsset · f2a8d52e
      Christian Brauner authored 
      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: default avatarChristian Brauner <christian.brauner@ubuntu.com>
Reviewed-by: default avatarSerge 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
      f2a8d52e
  5. 03 May, 2020 4 commits
  7. 02 May, 2020 8 commits
    • Linus Torvalds's avatar
      Merge tag 'pm-5.7-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm · 743f0573
      Linus Torvalds authored 
      Pull power management fixes from Rafael Wysocki:

 - prevent the intel_pstate driver from printing excessive diagnostic
   messages in some cases (Chris Wilson)

 - make the hibernation restore kernel freeze kernel threads as well as
   user space tasks (Dexuan Cui)

 - fix the ACPI device PM disagnostic messages to include the correct
   power state name (Kai-Heng Feng).

* tag 'pm-5.7-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
  PM: ACPI: Output correct message on target power state
  PM: hibernate: Freeze kernel threads in software_resume()
  cpufreq: intel_pstate: Only mention the BIOS disabling turbo mode once
      743f0573
    • Rafael J. Wysocki's avatar
      Merge branches 'pm-cpufreq' and 'pm-sleep' · a5383996
      Rafael J. Wysocki authored 
      * pm-cpufreq:
  cpufreq: intel_pstate: Only mention the BIOS disabling turbo mode once

* pm-sleep:
  PM: hibernate: Freeze kernel threads in software_resume()
      a5383996
    • Linus Torvalds's avatar
      Merge tag 'iomap-5.7-fixes-1' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux · f66ed1eb
      Linus Torvalds authored 
      Pull iomap fix from Darrick Wong:
 "Hoist the check for an unrepresentable FIBMAP return value into
  ioctl_fibmap.

  The internal kernel function can handle 64-bit values (and is needed
  to fix a regression on ext4 + jbd2). It is only the userspace ioctl
  that is so old that it cannot deal"

* tag 'iomap-5.7-fixes-1' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux:
  fibmap: Warn and return an error in case of block > INT_MAX
      f66ed1eb
    • Linus Torvalds's avatar
      Merge tag 'nfs-for-5.7-4' of git://git.linux-nfs.org/projects/trondmy/linux-nfs · 29a47f45
      Linus Torvalds authored 
      Pull NFS client bugfixes from Trond Myklebust:
 "Highlights include:

  Stable fixes:
   - fix handling of backchannel binding in BIND_CONN_TO_SESSION

  Bugfixes:
   - Fix a credential use-after-free issue in pnfs_roc()
   - Fix potential posix_acl refcnt leak in nfs3_set_acl
   - defer slow parts of rpc_free_client() to a workqueue
   - Fix an Oopsable race in __nfs_list_for_each_server()
   - Fix trace point use-after-free race
   - Regression: the RDMA client no longer responds to server disconnect
     requests
   - Fix return values of xdr_stream_encode_item_{present, absent}
   - _pnfs_return_layout() must always wait for layoutreturn completion

  Cleanups:
   - Remove unreachable error conditions"

* tag 'nfs-for-5.7-4' of git://git.linux-nfs.org/projects/trondmy/linux-nfs:
  NFS: Fix a race in __nfs_list_for_each_server()
  NFSv4.1: fix handling of backchannel binding in BIND_CONN_TO_SESSION
  SUNRPC: defer slow parts of rpc_free_client() to a workqueue.
  NFSv4: Remove unreachable error condition due to rpc_run_task()
  SUNRPC: Remove unreachable error condition
  xprtrdma: Fix use of xdr_stream_encode_item_{present, absent}
  xprtrdma: Fix trace point use-after-free race
  xprtrdma: Restore wake-up-all to rpcrdma_cm_event_handler()
  nfs: Fix potential posix_acl refcnt leak in nfs3_set_acl
  NFS/pnfs: Fix a credential use-after-free issue in pnfs_roc()
  NFS/pnfs: Ensure that _pnfs_return_layout() waits for layoutreturn completion
      29a47f45
    • Linus Torvalds's avatar
      Merge tag 'dmaengine-fix-5.7-rc4' of git://git.infradead.org/users/vkoul/slave-dma · ed6889db
      Linus Torvalds authored 
      Pull dmaengine fixes from Vinod Koul:
 "Core:
   - Documentation typo fixes
   - fix the channel indexes
   - dmatest: fixes for process hang and iterations

  Drivers:
   - hisilicon: build error fix without PCI_MSI
   - ti-k3: deadlock fix
   - uniphier-xdmac: fix for reg region
   - pch: fix data race
   - tegra: fix clock state"

* tag 'dmaengine-fix-5.7-rc4' of git://git.infradead.org/users/vkoul/slave-dma:
  dmaengine: dmatest: Fix process hang when reading 'wait' parameter
  dmaengine: dmatest: Fix iteration non-stop logic
  dmaengine: tegra-apb: Ensure that clock is enabled during of DMA synchronization
  dmaengine: fix channel index enumeration
  dmaengine: mmp_tdma: Reset channel error on release
  dmaengine: mmp_tdma: Do not ignore slave config validation errors
  dmaengine: pch_dma.c: Avoid data race between probe and irq handler
  dt-bindings: dma: uniphier-xdmac: switch to single reg region
  include/linux/dmaengine: Typos fixes in API documentation
  dmaengine: xilinx_dma: Add missing check for empty list
  dmaengine: ti: k3-psil: fix deadlock on error path
  dmaengine: hisilicon: Fix build error without PCI_MSI
      ed6889db
    • Linus Torvalds's avatar
      Merge tag 'vfio-v5.7-rc4' of git://github.com/awilliam/linux-vfio · 690e2aba
      Linus Torvalds authored 
      Pull VFIO fixes from Alex Williamson:

 - copy_*_user validity check for new vfio_dma_rw interface (Yan Zhao)

 - Fix a potential math overflow (Yan Zhao)

 - Use follow_pfn() for calculating PFNMAPs (Sean Christopherson)

* tag 'vfio-v5.7-rc4' of git://github.com/awilliam/linux-vfio:
  vfio/type1: Fix VA->PA translation for PFNMAP VMAs in vaddr_get_pfn()
  vfio: avoid possible overflow in vfio_iommu_type1_pin_pages
  vfio: checking of validity of user vaddr in vfio_dma_rw
      690e2aba
    • Linus Torvalds's avatar
      Merge tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux · 42eb62d4
      Linus Torvalds authored 
      Pull arm64 fix from Catalin Marinas:
 "Add -fasynchronous-unwind-tables to the vDSO CFLAGS"

* tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux:
  arm64: vdso: Add -fasynchronous-unwind-tables to cflags
      42eb62d4
    • Linus Torvalds's avatar
      Merge tag 'io_uring-5.7-2020-05-01' of git://git.kernel.dk/linux-block · cf018530
      Linus Torvalds authored 
      Pull io_uring fixes from Jens Axboe:

 - Fix for statx not grabbing the file table, making AT_EMPTY_PATH fail

 - Cover a few cases where async poll can handle retry, eliminating the
   need for an async thread

 - fallback request busy/free fix (Bijan)

 - syzbot reported SQPOLL thread exit fix for non-preempt (Xiaoguang)

 - Fix extra put of req for sync_file_range (Pavel)

 - Always punt splice async. We'll improve this for 5.8, but wanted to
   eliminate the inode mutex lock from the non-blocking path for 5.7
   (Pavel)

* tag 'io_uring-5.7-2020-05-01' of git://git.kernel.dk/linux-block:
  io_uring: punt splice async because of inode mutex
  io_uring: check non-sync defer_list carefully
  io_uring: fix extra put in sync_file_range()
  io_uring: use cond_resched() in io_ring_ctx_wait_and_kill()
  io_uring: use proper references for fallback_req locking
  io_uring: only force async punt if poll based retry can't handle it
  io_uring: enable poll retry for any file with ->read_iter / ->write_iter
  io_uring: statx must grab the file table for valid fd
      cf018530
  9. 01 May, 2020 19 commits
  11. 30 Apr, 2020 6 commits
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