[1.1] runc run: fix mount leak #4425
Merged
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
kolyshkin
force-pushed
the
1.1-fix-mount-leak
branch
from
af1fc06 to
b17d0b0
Compare
When preparing to mount container root, we need to make its parent mount private (i.e. disable propagation), otherwise the new in-container mounts are leaked to the host. To find a parent mount, we use to read mountinfo and find the longest entry which can be a parent of the container root directory. Unfortunately, due to kernel bug in all Linux kernels older than v5.8 (see [1], [2]), sometimes mountinfo can't be read in its entirety. In this case, getParentMount may occasionally return a wrong parent mount. As a result, we do not change the mount propagation to private, and container mounts are leaked. Alas, we can not fix the kernel, and reading mountinfo a few times to ensure its consistency (like it's done in, say, Kubernetes) does not look like a good solution for performance reasons. Fortunately, we don't need mountinfo. Let's just traverse the directory tree, trying to remount it private until we find a mount point (any error other than EINVAL means we just found it). Fixes issue 2404. [1]: https://github.com/kolyshkin/procfs-test [2]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=9f6c61f96f2d97cbb5f Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com> (cherry picked from commit 13a6f56) Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
kolyshkin
force-pushed
the
1.1-fix-mount-leak
branch
from
b17d0b0 to
65aa700
Compare
Merged
cyphar
approved these changes
Oct 3, 2024
AkihiroSuda
approved these changes
Oct 4, 2024
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
This is a backport of #4417 to release-1.1.
When preparing to mount container root, we need to make its parent mount private (i.e. disable propagation), otherwise the new in-container mounts are leaked to the host.
To find a parent mount, we use to read mountinfo and find the longest entry which can be a parent of the container root directory.
Unfortunately, due to kernel bug in all Linux kernels older than v5.8 (see 1, 2), sometimes mountinfo can't be read in its entirety. In this case, getParentMount may occasionally return a wrong parent mount.
As a result, we do not change the mount propagation to private, and container mounts are leaked.
Alas, we can not fix the kernel, and reading mountinfo a few times to ensure its consistency (like it's done in, say, Kubernetes) does not look like a good solution for performance reasons.
Fortunately, we don't need mountinfo. Let's just traverse the directory tree, trying to remount it private until we find a mount point (any error other than EINVAL means we just found it).
Fixes issue 2404.
Signed-off-by: Kir Kolyshkin kolyshkin@gmail.com
(cherry picked from commit 13a6f56)
Signed-off-by: Kir Kolyshkin kolyshkin@gmail.com