As with /dev symlinks, this was missed in commit d40b3439a9 ("rootfs:
switch to fd-based handling of mountpoint targets"). It's not really
clear to what extent this was exploitable (/sys/fs/cgroup is a tmpfs we
create) but it's better to just fix this anyway.
Fixes: d40b3439a9 ("rootfs: switch to fd-based handling of mountpoint targets")
Signed-off-by: Aleksa Sarai <aleksa@amutable.com>
(cherry picked from commit 66acd48f9d)
Signed-off-by: Aleksa Sarai <aleksa@amutable.com>
These codepaths are very old and operate on pure paths but before
pivot_root(2), meaning that a bad image with a malicious /dev symlink
could cause us to operate on host paths instead.
In practice this means that we could be tricked into removing a file
called "ptmx" (note that /dev/pts/ptmx and /dev/ptmx are both immune for
different reasons) or creating a very restricted set of symlinks (with
fixed targets and names). The scope of these bugs is thus quite limited,
but we definitely need to harden against it.
These codepaths were unfortunately missed during the fd-based rework in
commit d40b3439a9 ("rootfs: switch to fd-based handling of mountpoint
targets") -- I must've assumed they were called after pivot_root(2)...
Fixes: GHSA-xjvp-4fhw-gc47
Fixes: CVE-2026-41579
Fixes: d40b3439a9 ("rootfs: switch to fd-based handling of mountpoint targets")
Signed-off-by: Aleksa Sarai <aleksa@amutable.com>
(cherry picked from commit 864db8042d)
Signed-off-by: Aleksa Sarai <aleksa@amutable.com>
This argument order matches most other helpers we have and will also
match the changes we are about to make to setupPtmx and
setupDevSymlinks.
Signed-off-by: Aleksa Sarai <aleksa@amutable.com>
(cherry picked from commit fcf04eb41b)
Signed-off-by: Aleksa Sarai <aleksa@amutable.com>
This removes `mips64le` (no longer supported by the image / upstream in Debian Trixie+) and adds `riscv64`.
Signed-off-by: Tianon Gravi <admwiggin@gmail.com>
(cherry picked from commit ce5400da08)
Signed-off-by: Ricardo Branco <rbranco@suse.de>
The test checked for the exact BusyBox ash diagnostic "sh: can't fork".
With BusyBox 1.38, ash reports the failure as:
/bin/sh: line 0: can't fork: Resource temporarily unavailable
Match the stable "can't fork" part of the error message instead.
Signed-off-by: Ricardo Branco <rbranco@suse.de>
(cherry picked from commit de39d5e79b)
Signed-off-by: Ricardo Branco <rbranco@suse.de>
TestPids used long hand-written /bin/true pipelines for the 4-, 32- and
64-command cases. This made the test easy to typo and hard to review, as
seen by the earlier "bin/true" entries.
Build the shell pipelines instead, preserving the existing test coverage
while making the command counts explicit.
Signed-off-by: Ricardo Branco <rbranco@suse.de>
(cherry picked from commit 3acb097f93)
Signed-off-by: Ricardo Branco <rbranco@suse.de>
Close the root file descriptor immediately after use in maskPaths to
reduce the window during which an attacker could potentially exploit
an open fd to access or manipulate the root filesystem. This follows
the principle of least privilege and mitigates risks in compromised
or malicious container scenarios.
Co-authored-by: Kir Kolyshkin <kolyshkin@gmail.com>
Signed-off-by: lifubang <lifubang@acmcoder.com>
(cherry picked from commit b88635e57e)
Signed-off-by: lifubang <lifubang@acmcoder.com>
This is a follow-up to #5275. That change reused a single tmpfs mount
to mask multiple directories, which is efficient when masking more than
one path. However, it introduced unnecessary overhead when only one
directory is masked. This commit restores the original behavior for the
single-path case while preserving shared tmpfs logic for multiple paths.
Signed-off-by: lifubang <lifubang@acmcoder.com>
(cherry picked from commit e7e2f00248)
Signed-off-by: lifubang <lifubang@acmcoder.com>
Kubernetes may add one sysfs thermal_throttle entry per CPU to
maskedPaths. On large Intel systems this can produce many directory
masks for a single container. runc currently handles each directory
mask with a separate read-only tmpfs mount, and therefore a separate
tmpfs superblock.
On Linux 4.18/RHEL 8 kernels, creating and tearing down many tmpfs
superblocks can contend on the global shrinker_rwsem when containers
start or stop concurrently.
Use one read-only tmpfs for directory masks and bind-mount it over the
remaining directory targets. The first non-procfs-fd directory mount is
reopened through the container root fd before it is reused. File masks
still bind /dev/null, and procfs fd targets keep the existing
one-tmpfs-per-target behaviour because they are fd aliases rather than
stable rootfs paths.
If the bind-mount of the shared source fails (e.g. due to kernel
restrictions), fall back to individual tmpfs mounts for all remaining
directories. Tmpfs mounts use nr_blocks=1,nr_inodes=1 to minimise
kernel resource usage.
The bind mounts do not create additional tmpfs superblocks. They also
retain the read-only mount flag inherited from the source vfsmount, so
the masking semantics remain unchanged.
xref: kubernetes/kubernetes#138512
xref: kubernetes/kubernetes#138388
xref: kubernetes/kubernetes#131018
Co-authored-by: Davanum Srinivas <davanum@gmail.com>
Refactored-by: lifubang <lifubang@acmcoder.com>
Signed-off-by: lifubang <lifubang@acmcoder.com>
(cherry picked from commit c046c9b973)
Signed-off-by: lifubang <lifubang@acmcoder.com>
Previously, masked directories (e.g., /proc/acpi, /proc/scsi) were
mounted as read-only tmpfs without explicit size or inode limits.
Although these mounts are meant to be empty and unwritable, the lack
of resource constraints means that—should an attacker bypass the
read-only protection (e.g., via container escape, mount namespace
manipulation, or a kernel vulnerability)—the tmpfs could consume up
to 50% of system memory by default (the kernel's default tmpfs limit).
To mitigate this risk in high-density container environments and
adhere to the principle of least privilege, we now explicitly set:
- nr_blocks=1 (sufficient for at most one block size)
- nr_inodes=1 (sufficient for at most one inode)
Ref: https://man7.org/linux/man-pages/man5/tmpfs.5.html
These limits ensure that even if compromised, kernel memory usage
remains strictly bounded and negligible.
This change aligns with best practices used by other container
runtimes and strengthens defense-in-depth for sensitive masked paths.
Co-authored-by: Davanum Srinivas <davanum@gmail.com>
Refactored-by: lifubang <lifubang@acmcoder.com>
Signed-off-by: lifubang <lifubang@acmcoder.com>
(cherry picked from commit e57a7a4c8f)
Signed-off-by: lifubang <lifubang@acmcoder.com>
A lot of filesystem-related stuff happens inside the container root
directory, and we have used its name before. It makes sense to pre-open
it and use a *os.File handle instead.
Function names in internal/pathrs are kept as is for simplicity (and it
is an internal package), but they now accept root as *os.File.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
(cherry picked from commit 28cb321887)
Signed-off-by: lifubang <lifubang@acmcoder.com>
No change in functionality, just a preparation for the next patch.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
(cherry picked from commit 78b80677f6)
Signed-off-by: lifubang <lifubang@acmcoder.com>
Indeed, it does not make sense to prepend c.root once we started using
MkdirAllInRoot in commit 63c29081.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
(cherry picked from commit 60352524d3)
Signed-off-by: lifubang <lifubang@acmcoder.com>
As runc binary grows in size over time (new features, more
dependencies) some tests start to flake because of low memory limits.
One such test is "runc run (cgroup v2 resources.unified override)";
it obviously fails because of 1M memory limit:
> runc run failed: unable to start container process: container init was OOM-killed (memory limit too low?)
Increase the limits 4x. Do the same for the "unified only" test.
Fixes issue 5264.
Reported-by: Kevin Berry <kpberry11@gmail.com>
Reported-by: Ricardo Branco <rbranco@suse.de>
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
(cherry picked from commit 3fabb4d070)
Signed-off-by: lifubang <lifubang@acmcoder.com>
Co-authored-by: Claude <noreply@anthropic.com>
Those tests were added by commit 8d180e96 ("Add support for Linux
Network Devices"), apparently by copy-pasting the test cases which
call simple_cr (all four of them).
While different simple_cr tests make sense as they cover different
code paths in runc and/or check for various regression, the same
variations with netdevice do not make sense, as having a net device
is orthogonal to e.g. bind mount, --debug, or cgroupns.
Remove those.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
(cherry picked from commit 2cd4782b70)
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
In our bats tests, runc itself is a wrapper which calls bats run helper,
so using "run runc" is wrong as it results in calling run helper twice.
Fixes: 8d180e965
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
(cherry picked from commit ad72eab6c7)
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
This is a bit opinionated, but some comments in integration tests do not
really help to understand the nature of the tests being performed by
stating something very obvious, like
# run busybox detached
runc run -d busybox
To make things worse, these not-so-helpful messages are being
copy/pasted over and over, and that is the main reason to remove them.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
(cherry picked from commit 0eb03ef86f)
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
When RUNC_USE_SYSTEMD is set, tests/rootless.sh is using
ssh -tt rootless@localhost
to run tests as rootless user. In this case, local environment is not
passed to the user's ssh session (unless explicitly specified), and so
the tests do not get ROOTLESS_FEATURES.
As a result, idmap-related tests are skipped when running as rootless
using systemd cgroup driver:
integration test (systemd driver)
...
[02] run rootless tests ... (idmap)
...
ok 286 runc run detached ({u,g}id != 0) # skip test requires rootless_idmap
...
Fix this by creating a list of environment variables needed by the
tests, and adding those to ssh command line (in case of ssh) or
exporting (in case of sudo) so both cases work similarly.
Also, modify disable_idmap to unset variables set in enable_idmap so
they are not exported at all if idmap is not in features.
Fixes: bf15cc99 ("cgroup v2: support rootless systemd")
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
(cherry picked from commit 3e0829d195)
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
When signal installation was moved to a goroutine for performance,
containers that exited quickly could complete before SIGCHLD was
registered, causing runc to hang waiting for the signal.
This fix ensures SIGCHLD is registered immediately in the main thread
before other signals are handled in the goroutine, maintaining performance
while guaranteeing no missed SIGCHLD notifications for fast-exiting
containers.
Reported-by: Ayato Tokubi <atokubi@redhat.com>
Signed-off-by: lifubang <lifubang@acmcoder.com>
(cherry picked from commit 404181e4cc)
Signed-off-by: lifubang <lifubang@acmcoder.com>
This commit factors out setupAndMountToRootfs without changing any
logic. Use "Hide whitespace changes" during review to focus on the
actual changes.
The refactor ensures the mount source file descriptor is closed via
defer in each loop iteration, reducing the total number of open FDs
in runc. This helps avoid hitting the file descriptor limit under
high concurrency or when handling many mounts.
Signed-off-by: lifubang <lifubang@acmcoder.com>
(cherry picked from commit c77e71a3e7)
Signed-off-by: lifubang <lifubang@acmcoder.com>
This adds a CI job to run conmon tests with runc.
Related to issue 5151, PR 5153.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
(cherry picked from commit 192e3d416f)
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
Found out that these changes were backported to release-1.4 (PR 5040)
and made its way into runc v1.4.0, but were missing from its CHANGELOG.
Add the item to v1.4.0 changelog.
Same as commit e232a54 in main branch.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
Aleksa Sarai