When opening the peer end of a pty, the old kernel API required us to
open /dev/pts/$num inside the container (at least since we fixed console
handling many years ago in commit 244c9fc426 ("*: console rewrite")).
The problem is that in a hostile container it is possible for
/dev/pts/$num to be an attacker-controlled symlink that runc can be
tricked into resolving when doing bind-mounts. This allows the attacker
to (among other things) persist /proc/... entries that are later masked
by runc, allowing an attacker to escape through the kernel.core_pattern
sysctl (/proc/sys/kernel/core_pattern). This is the original issue
reported by Lei Wang and Li Fu Bang in CVE-2025-52565.
However, it should be noted that this is not entirely a newly-discovered
problem. Way back in Linux 4.13 (2017), I added the TIOCGPTPEER ioctl,
which allows us to get a pty peer without touching the /dev/pts inside
the container. The original threat model was around an attacker
replacing /dev/pts/$n or /dev/pts/ptmx with some malicious inode (a DoS
inode, or possibly a PTY they wanted a confused deputy to operate on).
Unfortunately, there was no practical way for runc to cache a safe
O_PATH handle to /dev/pts/ptmx (unlike other runtimes like LXC, which
switched to TIOCGPTPEER way back in 2017). Since it wasn't clear how we
could protect against the main attack TIOCGPTPEER was meant to protect
against, we never switched to it (even though I implemented it
specifically to harden container runtimes).
Unfortunately, It turns out that mount *sources* are a threat we didn't
fully consider. Since TIOCGPTPEER already solves this problem entirely
for us in a race free way, we should just use that. In a later patch, we
will add some hardening for /dev/pts/$num opening to maintain support
for very old kernels (Linux 4.13 is very old at this point, but RHEL 7
is still kicking and is stuck on Linux 3.10).
Fixes: GHSA-qw9x-cqr3-wc7r CVE-2025-52565
Reported-by: Lei Wang <ssst0n3@gmail.com> (CVE-2025-52565)
Reported-by: lfbzhm <lifubang@acmcoder.com> (CVE-2025-52565)
Reported-by: Aleksa Sarai <cyphar@cyphar.com> (TIOCGPTPEER)
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
Currently, we rely on mount returning ENOTDIR when the destination is a
directory (and so mount tells us that the source is not), and fall back
to read-only tmpfs bind mount for such cases.
Theoretically, ENOTDIR can also be returned in some other cases,
resulting in the wrong type of mount being used.
Let's be more straightforward here -- call fstat on destination file
descriptor, and use the proper mount depending on whether it is a
directory.
Reported-by: Rodrigo Campos <rodrigoca@microsoft.com>
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
When mounting a path being masked, the /dev/null might disappear from
under us, and mount (even on an opened /dev/null file descriptor) will
return ENOENT, which we deliberately ignore, as there's no need to mask
non-existent paths.
Let's open the destination path and ignore ENOENT during open, then
mount via the destination file descriptor, not ignoring ENOENT.
Reported-by: lifubang <lifubang@acmcoder.com>
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
The /dev/null in a container should not be trusted, because when /dev
is a bind mount, /dev/null is not created by runc itself.
1. Add isDevNull which checks the fd minor/major and device type,
and verifyDevNull which does the stat and the check.
2. Rewrite maskPath to open and check /dev/null, and use its fd to
perform mounts. Move the loop over the MaskPaths into the function,
and rename it to maskPaths.
3. reOpenDevNull: use verifyDevNull and isDevNull.
4. fixStdioPermissions: use isDevNull instead of stat.
Fixes: GHSA-9493-h29p-rfm2 CVE-2025-31133
Co-authored-by: Rodrigo Campos <rodrigoca@microsoft.com>
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
filepath-securejoin v0.3 gave us a much safer re-open primitive, we
should use it to avoid any theoretical attacks. Rather than using it
direcly, add a small pathrs wrapper to make libpathrs migrations in the
future easier...
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
We will have more wrappers around filepath-securejoin, and so move them
to their own specific package so that we can eventually use libpathrs
fairly cleanly (by swapping out the implementation).
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
This will be used for a few security patches in later patches in this
patchset. The need to verify what kind of inode we are operating on in a
race-free way turns out to be quite a common pattern...
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
This is necessary for the pre-1.4 backports because internal/linux was
not present and the linters get angry when a new package without a doc
comment gets added.
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
(Backported by Jared Ledvina.)
dependabot[bot]:
build(deps): bump github.com/opencontainers/cgroups from 0.0.3 to 0.0.4
Kir Kolyshkin (4):
deps: bump cgroups to v0.0.3, fix tests
libct: State: ensure Resources is not nil
deps: bump opencontainers/cgroups to v0.0.2
tests/int: simplify using check_cpu_quota
LGTMs: kolyshkin cyphar
Since opencontainers/cgroups v0.0.2 (commit b206a015), all stuct
Resources fields are annotated with "omitempty" attribute.
As a result, the loaded configuration may have Resources == nil.
It is totally OK (rootless containers may have no resources configured)
except since commit 6c5441e5, cgroup v1 fs manager requires Resources to
be set in the call to NewManager (this is a cgroup v1 deficiency,
or maybe our implementation deficiency, or both).
To work around this, let's add code to ensure Resources is never nil
after loading from state.json.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
Instead of providing systemd CPU quota value (CPUQuotaPerSec),
calculate it based on how opencontainers/cgroups/systemd handles
it (see addCPUQuota).
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
When a non–page-aligned value is written to memory.max, the kernel aligns it
down to the nearest page boundary. On systems with a page size greater
than 4K (e.g., 64K), this caused failures because the configured
memory.max value was not 64K aligned.
This patch fixes the issue by explicitly aligning the memory.max value
to 64K. Since 64K is also a multiple of 4K, the value is correctly
aligned on both 4K and 64K page size systems.
However, this approach will still fail on systems where the hardcoded
memory.max value is not aligned to the system page size.
Fixes: https://github.com/opencontainers/runc/issues/4841
Signed-off-by: Vishal Chourasia <vishalc@linux.ibm.com>
Signed-off-by: Donet Tom <donettom@linux.ibm.com>
(cherry picked from commit 830c479ae2)
Signed-off-by: Rodrigo Campos <rodrigoca@microsoft.com>
Instead of generating a list of tmpfs mount and have a special function
to check whether the path is in the list, let's go over the list of
mounts directly. This simplifies the code and improves readability.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
(cherry picked from commit ce3cd4234c)
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
Since its code is now trivial, and it is only called from a single
place, it does not make sense to have it as a separate function.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
(cherry picked from commit f91fbd34d9)
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
It makes sense to ignore cgroup mounts much early in the code,
saving some time on unnecessary operations.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
(cherry picked from commit b8aa5481db)
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
1. Replace the big "if !" block with the if block and continue,
simplifying the code flow.
2. Move comments closer to the code, improving readability.
This commit is best reviewed with --ignore-all-space or similar.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
(cherry picked from commit 0c93d41c65)
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
In certain deployments, it's possible for runc to be spawned by a
process with a restrictive cpumask (such as from a systemd unit with
CPUAffinity=... configured) which will be inherited by runc and thus the
container process by default.
The cpuset cgroup used to reconfigure the cpumask automatically for
joining processes, but kcommit da019032819a ("sched: Enforce user
requested affinity") changed this behaviour in Linux 6.2.
The solution is to try to emulate the expected behaviour by resetting
our cpumask to correspond with the configured cpuset (in the case of
"runc exec", if the user did not configure an alternative one). Normally
we would have to parse /proc/stat and /sys/fs/cgroup, but luckily
sched_setaffinity(2) will transparently convert an all-set cpumask (even
if it has more entries than the number of CPUs on the system) to the
correct value for our usecase.
For some reason, in our CI it seems that rootless --systemd-cgroup
results in the cpuset (presumably temporarily?) being configured such
that sched_setaffinity(2) will allow the full set of CPUs. For this
particular case, all we care about is that it is different to the
original set, so include some special-casing (but we should probably
investigate this further...).
Reported-by: ningmingxiao <ning.mingxiao@zte.com.cn>
Reported-by: Martin Sivak <msivak@redhat.com>
Reported-by: Peter Hunt <pehunt@redhat.com>
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
(Cherry-pick of commit 121192ade6c55f949d32ba486219e2b1d86898b2.)
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
Sometimes we need to run runc through some wrapper (like nohup), but
because "__runc" and "runc" are bash functions in our test suite this
doesn't work trivially -- and you cannot just pass "$RUNC" because you
you need to set --root for rootless tests.
So create a setup_runc_cmdline helper which sets $RUNC_CMDLINE to the
beginning cmdline used by __runc (and switch __runc to use that).
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
(Cherry-pick of commit d1f6acfab06e6f5eb15b7edfaa704f50907907b1.)
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
"runc" was a special wrapper around bats's "run" which output some very
useful diagnostic information to the bats log, but this was not usable
for other commands. So let's make it a more generic helper that we can
use for other commands.
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
(Cherry-pick of commit ea385de40c9a006737399bc72918a19e5d038736.)
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
The issue on arm [1] is now fixed, so let's get back to using the
packaged criu version for most of the CI matrix.
This reverts commit 105674844e
("ci: use criu built from source on gha arm").
[1]: https://github.com/checkpoint-restore/criu/issues/2709
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
(Cherry-picked from commit 96f4a90a6b1ca9e3f2011ebaeffb7dc52db2ca32.)
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
Currently, criu package from opensuse build farm times out on GHA arm,
so let's only use criu-dev (i.e. compiled from source on CI machine).
Once this is fixed, this patch can be reverted.
Related to criu issue 2709.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
(Cherry-picked from commit 105674844eaaf24bf14135ef0c64703e511882ab.)
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
Since GHA now provides ARM, we can switch away from actuated.
Many thanks to @alexellis (@self-actuated) for being the sponsor of this
project.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
(Cherry-picked from commit 1cf096803abb770c414ce0a1e2e0be283b09001d.)
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
Prevent --l3-cache-schema from clearing the intel_rdt.memBwSchema state
and --mem-bw-schema clearing l3_cache_schema, respectively.
Signed-off-by: Markus Lehtonen <markus.lehtonen@intel.com>
(cherry picked from commit 57b6a317bb)
This was added in 2ee9cbbd12 ("It's /proc/stat, not /proc/stats") with
no actual justification, and doesn't really make much sense on further
inspection:
* /proc/net is a symlink to "self/net", which means that /proc/net/dev
is a per-process file, and so overmounting it would only affect pid1.
Any other program that cares about /proc/net/dev would see their own
process's configuration, and unprivileged processes wouldn't be able
to see /proc/1/... data anyway.
In addition, the fact that this is a symlink means that runc will
deny the overmount because /proc/1/net/dev is not in the proc
overmount allowlist. This means that this has not worked for many
years, and probably never worked in the first place.
* /proc/self/net is already namespaced with network namespaces, so the
primary argument for allowing /proc overmounts (lxcfs-like masking of
procfs files to emulate namespacing for files that are not properly
namespaced for containers -- such as /proc/cpuinfo) is moot.
It goes without saying that lxcfs has never overmounted
/proc/self/net/... files, so the general "because lxcfs"
justification doesn't hold water either.
* The kernel has slowly been moving towards blocking overmounts in
/proc/self/. Linux 6.12 blocked overmounts for fd, fdinfo, and
map_files; future Linux versions will probably end up blocking
everything under /proc/self/.
Fixes: 2ee9cbbd12 ("It's /proc/stat, not /proc/stats")
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
(cherry-picked from commit 3620185d06b79da836559b75161027c6273fff7b.)
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
The dmem controller is added into kernel v6.13 and is now enabled in
Fedora 42 kernels. Yet, systemd is not aware of dmem.
This fixes the test case failure on Fedora.
For the initial test case, see commit 27515719.
For earlier commits similar to this one, see
commits 601cf582, 05272718, e83ca519.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
(cherry picked from commit b3432118ed)
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
The per-file deprecation in cgroup_deprecated.go is not working,
let's replace it.
Link to Hooks.Run in Hook.Run deprecation notice.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
(cherry picked from commit b25bcaa8b3)
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
Aleksa Sarai