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>
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>
This function calls Init what normally never returns, so the defer only
works if there is an error and we can safely use it to close those fds
we opened. This was done for most but not all fds.
Reported in issue 5008.
Reported-by: Arina Cherednik <arinacherednik034@gmail.com>
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
(cherry picked from commit 88f897160c)
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
This includes a few fixes for 32-bit builds.
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
(cherry picked from commit b58e342758)
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
Ever since v0.6.0 of github.com/cyphar/filepath-securejoin, pathrs-lite
has been able to transparently switch to using libpathrs as the backend
for safe path resolution (at compile-time, using a build tag). Note that
because build-tags apply globally, this allows for us to easily opt
pure-Go dependencies into all using libpathrs as well for our binaries.
In a future patch this will likely be enabled by default, but document
that this is an option for downstreams that want to opt-in to using
libpathrs.
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
(cherry picked from commit ab6f75dd25)
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
In a future patch this will contain other cdylibs so it deserves a
slightly more general name.
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
(cherry picked from commit 8292574e7a)
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
The intention of commit 531e29e192 ("script/lib.sh: set GOARM=5 for
armel, GOARM=6 for armhf") was to properly support older ARM platforms
with our release builds.
However, we have never been able to support ARMv6 for our builds because
we use the Debian compiler to build the libseccomp we statically compile
into our binaries and (as per the now-deleted comment itself) Debian
treats armhf as being ARMv7 so the final binaries we produced were
always only ever compatible with ARMv7+.
This was a bit of an oddity before but when building libpathrs for
releases we will need to use Rust which makes the target more explicit
(and while it does support armhf, we are using the Debian-packaged Rust
cross-compiler and thus are in the same dilemma with what Debian
considers "armhf" to be).
All-in-all, it's better to just bite the bullet and just follow Debian
here properly.
Fixes: 531e29e192 ("script/lib.sh: set GOARM=5 for armel, GOARM=6 for armhf")
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
(cherry picked from commit 51ae8de054)
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
Debian 13 (trixie) was released a few months ago and it's probably
prudent to just upgrade. This is also necessary to get access to riscv64
repositories when we build libpathrs for inclusion in our runc binaries.
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
(cherry picked from commit 6b757b6aa0)
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
lifubang