Work around tmpfs default permissions regression in runc 1.3.3#1964
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Work around tmpfs default permissions regression in runc 1.3.3#1964
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The Python classic repo's CI just started failing in the container-test job with: `mkdir: cannot create directory '/app/.heroku': Permission denied` eg: https://github.com/heroku/heroku-buildpack-python/actions/runs/19368179568/job/55418539741 After updating Docker locally, I was able to reproduce the error, and have found it's due to the recent runc 1.33 release: https://github.com/opencontainers/runc/releases/tag/v1.3.3 This runc release includes a number of security fixes - however, one of which has a regression: opencontainers/runc#4971 There is a fix for this upstream: opencontainers/runc#4973 ...but it's not released yet. However, we can work around the issue by explicitly setting the previous tmpfs permissions using `:mode=1777`: https://docs.docker.com/engine/storage/tmpfs/#options-for---tmpfs GUS-W-20221627.
colincasey
approved these changes
Nov 14, 2025
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The Python classic repo's CI just started failing in the container-test job with:
mkdir: cannot create directory '/app/.heroku': Permission deniedeg:
https://github.com/heroku/heroku-buildpack-python/actions/runs/19368179568/job/55418539741
After updating Docker locally, I was able to reproduce the error, and have found it's due to the recent runc 1.3.3 release: https://github.com/opencontainers/runc/releases/tag/v1.3.3
This runc release includes a number of security fixes, one of which has a regression:
opencontainers/runc#4971
There is a fix for this upstream:
opencontainers/runc#4973
...but it's not released yet.
However, we can work around the issue by explicitly setting the previous tmpfs permissions using
:mode=1777:https://docs.docker.com/engine/storage/tmpfs/#options-for---tmpfs
GUS-W-20221627.