Fix SIGCHLD race in signal handler setup by lifubang · Pull Request #5210 · opencontainers/runc

lifubang · 2026-04-01T01:29:37Z

This is an alternative to #5206.
Fix: #5208

When signal installation was moved to a goroutine for performance(#4654), 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

kolyshkin · 2026-04-01T17:44:00Z

 	}
 	handler := make(chan *signalHandler)
+
+	// ensure that we have a large buffer size so that we do not miss any


a very minor nit:

Suggested change

// ensure that we have a large buffer size so that we do not miss any

// Ensure that we have a large buffer size so that we do not miss any

kolyshkin

LGTM

kolyshkin · 2026-04-01T17:46:39Z

 	// setup.
+	// But `SIGCHLD` is very important, so we need to handle it immediately.


Suggested change

// setup.

// But `SIGCHLD` is very important, so we need to handle it immediately.

- // setup.

+ // setup, except for SIGCHLD which is very important (see #5208).

kolyshkin · 2026-04-01T18:09:45Z

I want to include this into 1.5.0rc2, @opencontainers/runc-maintainers ptal

kolyshkin · 2026-04-02T00:24:42Z

@lifubang feel free to merge as is or modify the comments, either way is fine with me. Once merged, please open an 1.5 backport, I want to release rc2 asap

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>

This PR contains the following updates: | Package | Type | Update | Change | OpenSSF | |---|---|---|---|---| | [github.com/opencontainers/runc](https://github.com/opencontainers/runc) | require | patch | `v1.4.1` → `v1.4.2` | [![OpenSSF Scorecard](https://api.securityscorecards.dev/projects/github.com/opencontainers/runc/badge)](https://securityscorecards.dev/viewer/?uri=github.com/opencontainers/runc) | --- > ⚠️ **Warning** > > Some dependencies could not be looked up. Check the [Dependency Dashboard](issues/23) for more information. --- ### Release Notes <details> <summary>opencontainers/runc (github.com/opencontainers/runc)</summary> ### [`v1.4.2`](https://github.com/opencontainers/runc/releases/tag/v1.4.2): runc v1.4.2 -- "Я — Земля! Я своих провожаю питомцев" [Compare Source](opencontainers/runc@v1.4.1...v1.4.2) This is the second patch release of the 1.4.z release series of runc. ##### Fixed - A regression in runc v1.3.0 which can result in a stuck `runc exec` or `runc run` when the container process runs for a short time. ([#5208](opencontainers/runc#5208), [#5210](opencontainers/runc#5210), [#5216](opencontainers/runc#5216)) - Mount sources that need to be open on the host are now closed earlier during container start, reducing the total amount of used file descriptors and helping to avoid hitting the open files limit when handling many such mounts. ([#5177](opencontainers/runc#5177), [#5201](opencontainers/runc#5201)) ##### Static Linking Notices The `runc` binary distributed with this release are *statically linked* with the following [GNU LGPL-2.1][lgpl-2.1] licensed libraries, with `runc` acting as a "work that uses the Library": [lgpl-2.1]: https://www.gnu.org/licenses/old-licenses/lgpl-2.1.en.html - [libseccomp](https://github.com/seccomp/libseccomp) The versions of these libraries were not modified from their upstream versions, but in order to comply with the LGPL-2.1 (§6(a)), we have attached the complete source code for those libraries which (when combined with the attached runc source code) may be used to exercise your rights under the LGPL-2.1. However we strongly suggest that you make use of your distribution's packages or download them from the authoritative upstream sources, especially since these libraries are related to the security of your containers. *** Thanks to the following contributors for making this release possible: - Ayato Tokubi <atokubi@redhat.com> - Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp> - Aleksa Sarai <cyphar@cyphar.com> - Kir Kolyshkin <kolyshkin@gmail.com> - Li Fubang <lifubang@acmcoder.com> - Rodrigo Campos Catelin <rodrigo@amutable.com> Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com> </details> --- ### Configuration 📅 **Schedule**: Branch creation - At 12:00 AM through 04:59 AM and 10:00 PM through 11:59 PM, Monday through Friday ( * 0-4,22-23 * * 1-5 ), Only on Sunday and Saturday ( * * * * 0,6 ) (UTC), Automerge - At any time (no schedule defined). 🚦 **Automerge**: Disabled by config. Please merge this manually once you are satisfied. ♻ **Rebasing**: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox. 🔕 **Ignore**: Close this PR and you won't be reminded about this update again. --- - [ ] If you want to rebase/retry this PR, check this box --- This PR has been generated by [Renovate Bot](https://github.com/renovatebot/renovate).  Reviewed-on: https://altlinux.space/stapler/stplr/pulls/387 Co-authored-by: Renovate Bot <stapler-helper-bot@noreply.altlinux.space> Co-committed-by: Renovate Bot <stapler-helper-bot@noreply.altlinux.space>

lifubang added the regression label Apr 1, 2026

lifubang mentioned this pull request Apr 1, 2026

Fix SIGCHLD race in signal handler setup #5206

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kolyshkin reviewed Apr 1, 2026

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kolyshkin approved these changes Apr 1, 2026

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kolyshkin force-pushed the fix-signal-race branch from 52e4032 to b594619 Compare April 1, 2026 17:47

kolyshkin requested review from AkihiroSuda and cyphar April 1, 2026 17:47

kolyshkin added backport/1.3-todo A PR in main branch which needs to be backported to release-1.3 backport/1.4-todo A PR in main branch which needs to backported to release-1.4 backport/1.5-todo A PR in main branch which needs to be backported to release-1.5 labels Apr 1, 2026

kolyshkin added this to the 1.5.0-rc.2 milestone Apr 1, 2026

AkihiroSuda approved these changes Apr 1, 2026

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lifubang force-pushed the fix-signal-race branch from b594619 to 404181e Compare April 2, 2026 00:59

lifubang mentioned this pull request Apr 2, 2026

[1.5] Fix SIGCHLD race in signal handler setup #5214

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lifubang merged commit 62d4f14 into opencontainers:main Apr 2, 2026
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This was referenced Apr 2, 2026

[1.3] Fix SIGCHLD race in signal handler setup #5215

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[1.4] Fix SIGCHLD race in signal handler setup #5216

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kolyshkin mentioned this pull request Apr 2, 2026

Release 1.4.2 #5217

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kolyshkin removed this from the 1.5.0-rc.2 milestone Apr 3, 2026

campaigner-prod Bot mentioned this pull request Apr 23, 2026

fix(deps): vuln minor upgrades — 15 packages (minor: 7 · patch: 8) DataDog/vault#87

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Fix SIGCHLD race in signal handler setup#5210

Fix SIGCHLD race in signal handler setup#5210
lifubang merged 1 commit intoopencontainers:mainfrom
lifubang:fix-signal-race

lifubang commented Apr 1, 2026

Uh oh!

kolyshkin Apr 1, 2026 •

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	// ensure that we have a large buffer size so that we do not miss any
	// Ensure that we have a large buffer size so that we do not miss any

		// setup.
		// But `SIGCHLD` is very important, so we need to handle it immediately.

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lifubang commented Apr 1, 2026

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kolyshkin Apr 1, 2026 •

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