google/gvisor

Implement /proc/sys/user/max_user_namespaces ?

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#11210 opened on Nov 22, 2024

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good first issuetype: enhancement

Description

Description

Bubblewrap with option "--disable-userns" enabled fails to run in gvisor due to lack of /proc/sys/user/max_user_namespaces (relevant code). The option "--disable-userns" is set as default by flatpak, so adding /proc/sys/user/max_user_namespaces will make it possible to build and run flatpak in container with gvisor.

Is this feature related to a specific bug?

No response

Do you have a specific solution in mind?

No response

Contributor guide

Tech stack
go
Domain
backendsecurity
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
3-5 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
mostly clear
Prerequisites
Linux namespace basicsprocfs in gVisorGo programming
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
15
Research direction
Examine the current implementation of /proc/sys in gVisor, particularly under /pkg/sentry/fs/proc/. Understand how other /proc/sys/user files are defined (e.g., /proc/sys/user/max user namespaces is missing). Look at the bubblewrap code linked to see how it reads this file. A new file must be added to the proc filesystem that returns a value (likely 0 or a configurable limit). Check existing tests for similar proc files.