This is effectively a revert of 2ac9968401, which
switched from os/exec to the golang.org/x/sys/execabs package to mitigate
security issues (mainly on Windows) with lookups resolving to binaries in the
current directory.
from the go1.19 release notes https://go.dev/doc/go1.19#os-exec-path
> ## PATH lookups
>
> Command and LookPath no longer allow results from a PATH search to be found
> relative to the current directory. This removes a common source of security
> problems but may also break existing programs that depend on using, say,
> exec.Command("prog") to run a binary named prog (or, on Windows, prog.exe) in
> the current directory. See the os/exec package documentation for information
> about how best to update such programs.
>
> On Windows, Command and LookPath now respect the NoDefaultCurrentDirectoryInExePath
> environment variable, making it possible to disable the default implicit search
> of “.” in PATH lookups on Windows systems.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
It's followup for #5890.
The containerd-shim process depends on the mount package to init rootfs
for container. For the container enable user namespace, the mount
package needs to fork child process to get the brand-new user namespace.
However, there are two reapers in one process (described by the
following list) and there are race-condition cases.
1. mount package
2. sys.Reaper as global one which watch all the SIGCHLD.
=== [kill(2)][kill] the wrong process ===
Currently, we use pipe to ensure that child process is alive. However,
the pide file descriptor can be hold by other process, which the child
process cannot exit by self. We should use [kill(2)][kill] to ensure the
child process. But we might kill the wrong process if the child process
might be reaped by containerd-shim and the PID might be reused by other
process.
=== [waitid(2)][waitid] on the wrong child process ===
```
containerd-shim process:
Goroutine 1(GetUsernsFD): Goroutine 2(Reaper)
1. Ready to wait for child process X
2. Received SIGCHLD from X
3. Reaped the zombie child process X
(X has been reused by other child process)
4. Wait on process X
The goroutine 1 will be stuck until the process X has been terminated.
```
=== open `/proc/X/ns/user` on the wrong child process ===
There is also pid-reused risk between opening `/proc/$pid/ns/user` and
writing `/proc/$pid/u[g]id_map`.
```
containerd-shim process:
Goroutine 1(GetUsernsFD): Goroutine 2(Reaper)
1. Fork child process X
2. Write /proc/X/uid_map,gid_map
3. Received SIGCHLD from X
4. Reaped the zombie child process X
(X has been reused by other process)
5. Open /proc/X/ns/user file as usernsFD
The usernsFD links to the wrong X!!!
```
In order to fix the race-condition, we should use [CLONE_PIDFD][clone2] (Since
Linux v5.2).
When we fork child process `X`, the kernel will return a process file
descriptor `X_PIDFD` referencing to child process `X`. With the pidfd, we can
use [pidfd_send_signal(2)][pidfd_send_signal] (Since Linux v5.1)
to send signal(0) to ensure the child process `X` is alive. If the `X` has
terminated and its PID has been recycled for another process. The
pidfd_send_signal fails with the error ESRCH.
Therefore, we can open `/proc/X/{ns/user,uid_map,gid_map}` file
descriptors as first and then use pidfd_send_signal to check the process
is still alive. If so, we can ensure the file descriptors are valid and
reference to the child process `X`. Even if the `X` PID has been reused
after pidfd_send_signal call, the file descriptors are still valid.
```code
X, pidfd = clone2(CLONE_PIDFD)
usernsFD = open /proc/X/ns/user
uidmapFD = open /proc/X/uid_map
gidmapFD = open /proc/X/gid_map
pidfd_send_signal pidfd, signal(0)
return err if no such process
== When we arrive here, we can ensure usernsFD/uidmapFD/gidmapFD are correct
== even if X has been reused after pidfd_send_signal call.
update uid/gid mapping by uidmapFD/gidmapFD
return usernsFD
```
And the [waitid(2)][waitid] also supports pidfd type (Since Linux 5.4).
We can use pidfd type waitid to ensure we are waiting for the correct
process. All the PID related race-condition issues can be resolved by
pidfd.
```bash
➜ mount git:(followup-idmapped) pwd
/home/fuwei/go/src/github.com/containerd/containerd/mount
➜ mount git:(followup-idmapped) sudo go test -test.root -run TestGetUsernsFD -count=1000 -failfast -p 100 ./...
PASS
ok github.com/containerd/containerd/mount 3.446s
```
[kill]: <https://man7.org/linux/man-pages/man2/kill.2.html>
[clone2]: <https://man7.org/linux/man-pages/man2/clone.2.html>
[pidfd_send_signal]: <https://man7.org/linux/man-pages/man2/pidfd_send_signal.2.html>
[waitid]: <https://man7.org/linux/man-pages/man2/waitid.2.html>
Signed-off-by: Wei Fu <fuweid89@gmail.com>
This patch introduces idmapped mounts support for
container rootfs.
The idmapped mounts support was merged in Linux kernel 5.12
torvalds/linux@7d6beb7.
This functionality allows to address chown overhead for containers that
use user namespace.
The changes are based on experimental patchset published by
Mauricio Vásquez #4734.
Current version reiplements support of idmapped mounts using Golang.
Performance measurement results:
Image idmapped mount recursive chown
BusyBox 00.135 04.964
Ubuntu 00.171 15.713
Fedora 00.143 38.799
Signed-off-by: Mauricio Vásquez <mauricio@kinvolk.io>
Signed-off-by: Artem Kuzin <artem.kuzin@huawei.com>
Signed-off-by: Alexey Perevalov <alexey.perevalov@huawei.com>
Signed-off-by: Ilya Hanov <ilya.hanov@huawei-partners.com>
The same attribute was generated for each path that was created, but always
the same, so instead of generating it in each iteration, generate it once,
and pass it to our mkdirall() implementation.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
The regex only matched volume paths without a trailing path-separator. In cases
where a path would be passed with a trailing path-separator, it would depend on
further code in mkdirall to strip the trailing slash, then to perform the regex
again in the next iteration.
While regexes aren't ideal, we're already executing this one, so we may as well
use it to match those situations as well (instead of executing it twice), to
allow us to return early.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
Ideally, we would construct this lazily, but adding a function and a
sync.Once felt like a bit "too much".
Also updated the GoDoc for some functions to better describe what they do.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
This function was forked from Moby in 6089c1525b,
which copied the whole file, but the `IsAbs()` was never used, and has no
external consumers, so let's remove it.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
ForceRemoveAll was only used in tests/fuzzing, but added hcsshim as dependency
for the sys package. Moving this to integration/client makes the "sys" package
slightly more lightweight, and may help simplifying dependency-management.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
These functions were originally copied from the docker / moby repository in
4a7a8efc2d. Migrating these functions to use the
github.com/moby/sys/sequential module allows them being shared between moby,
docker/cli, and containerd, and to allow using them without importing all of sys
which also depends on hcsshim and more.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
The channel is created with no capacity that it needs receiver when
sending data. Otherwise, the sending-data goroutine will be blocked
forever. For the #6166 pr, the exec command timeout will return and
no receiver for the data. It will cause goroutine leaky.
This commit allocates buffered channel for the command status and closes
the channel after sending. And also use time.Timer with Stop for
performance concern.
Signed-off-by: Wei Fu <fuweid89@gmail.com>
Some layers might be prefixed with rm-, which will result
in an error when converting that string into an integer.
Signed-off-by: Claudiu Belu <cbelu@cloudbasesolutions.com>
The io/ioutil package has been deprecated as of Go 1.16, see
https://golang.org/doc/go1.16#ioutil. This commit replaces the existing
io/ioutil functions with their new definitions in io and os packages.
Signed-off-by: Eng Zer Jun <engzerjun@gmail.com>
Go 1.15.7 contained a security fix for CVE-2021-3115, which allowed arbitrary
code to be executed at build time when using cgo on Windows. This issue also
affects Unix users who have “.” listed explicitly in their PATH and are running
“go get” outside of a module or with module mode disabled.
This issue is not limited to the go command itself, and can also affect binaries
that use `os.Command`, `os.LookPath`, etc.
From the related blogpost (ttps://blog.golang.org/path-security):
> Are your own programs affected?
>
> If you use exec.LookPath or exec.Command in your own programs, you only need to
> be concerned if you (or your users) run your program in a directory with untrusted
> contents. If so, then a subprocess could be started using an executable from dot
> instead of from a system directory. (Again, using an executable from dot happens
> always on Windows and only with uncommon PATH settings on Unix.)
>
> If you are concerned, then we’ve published the more restricted variant of os/exec
> as golang.org/x/sys/execabs. You can use it in your program by simply replacing
This patch replaces all uses of `os/exec` with `golang.org/x/sys/execabs`. While
some uses of `os/exec` should not be problematic (e.g. part of tests), it is
probably good to be consistent, in case code gets moved around.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
Remove build tags which are already implied by the name of the file.
Ensures build tags are used consistently
Signed-off-by: Derek McGowan <derek@mcg.dev>
It's the only location this is used, so might as well move it
into that package. I could not find external users of this utility,
so not adding an alias / deprecation.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
This removes the StatAtime(), StatCtime(), StatMtime() and StatATimeAsTime()
utilities from the sys package. These utilities are not currently used in the
containerd codebase, and a copy of these utilities can be found in
github.com/containerd/continuity/fs;
- fa7d162237/fs/stat_darwinbsd.go
- fa7d162237/fs/stat_linuxopenbsd.go
Given that the containerd/sys package is not designed for external consumption,
I'm not adding "deprecated" comments (or aliases to their new location).
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
ForceRemoveAll has special logic on Windows for cleaning up a Windows
snapshotter directory. The logic was missing proper handling for an
error case that can be returned in some cases.
This fixes the CI failure seen in #5326.
Signed-off-by: Kevin Parsons <kevpar@microsoft.com>
(this was introduced in 44240116aa)
Setting the oom-score-adj to -1000 is only possible if the parent process
either has no score set, or if the score is set to -1000.
However, the current implementation of GetOOMScoreAdj conflates situations
where either _no_ oom-score is set, _or_ oom-score is set, but set to 0.
In the latter case, the test would fail:
--- FAIL: TestSetOOMScoreBoundaries (0.01s)
oom_linux_test.go:79: assertion failed: 0 (adjustment int) != -1000 (OOMScoreAdjMin int)
FAIL
To prevent failures in this situation, skip that part of the test in the
above situation.
Also update the description of GetOOMScoreAdj to clarify its behavior.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
The shim.SetScore() utility was no longer used since 7dfc605fc6.
Checking for uses outside of this repository, I found only one external use of
this in gVisor; a9441aea27/pkg/shim/service.go (L262-L264)
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
SetOOMScore requires both privileged (root) and non-user namespace,
for negative values, so adjust the pre-conditions accordingly.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
These are currently only used inside this package, so we might
as well un-export them until we need them elsewhere.
Also updated SetOOMScore() to first check for privileged; check for privileged
looks to be the "faster" path, and checking it first could (in case of non-
privileged) save having to read and parse /proc/self/uid_map.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
This ensures that we do not trigger assertions inside HCS by tring to
call hcsshim.DestroyLayer on the parent of a currently-activated layer.
It also deactivates the layers before deletion, to ensure we trigger or
avert file-in-use failures due to leftover state from the tests with
more detail than 'destroy failed'.
Signed-off-by: Paul "TBBle" Hampson <Paul.Hampson@Pobox.com>
oom_score_adj must be in the range -1000 to 1000. In AdjustOOMScore if containerd's score is already at the maximum value we should set that value for the shim instead of trying to set 1001 which is invalid.
Signed-off-by: Simon Kaegi <simon_kaegi@ca.ibm.com>
GitHub Actions process wrapper sets score adj to 500 for any process;
the OOM score adj test expected default adj to be 0 during test.
Signed-off-by: Phil Estes <estesp@linux.vnet.ibm.com>
Dependencies may be switching to use the new `%w` formatting
option to wrap errors; switching to use `errors.Is()` makes
sure that we are still able to unwrap the error and detect the
underlying cause.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
