All my userns-remap enabled docker builds started failing when buildkit was enabled by default. Is this a buildkit bug?

[lufte]

Hi everybody. I'm trying to get a little clarity on a bug I'm getting to decide where exactly to report it.

When buildkit was enabled by default in docker (version 23) all my builds that include a RUN step started failing. I tracked it down to it being related to my use of userns-remap. I can run these builds if I deactivate buildkit or if I deactivate userns-remap, otherwise I get errors like the following one:

> [base  3/12] RUN echo "deb http://apt.postgresql.org/pub/repos/apt buster-pgdg main" > /etc/apt/sources.list.d/pgdg.list:                           
#0 0.373 runc run failed: unable to start container process: error during container init: error preparing rootfs: mount /var/lib/docker/1000.1000/build
kit/executor/uatv4lj8w8sud2ls21wcmm3nu/rootfs:/var/lib/docker/1000.1000/buildkit/executor/uatv4lj8w8sud2ls21wcmm3nu/rootfs, flags: 0x5000: permission d
enied                                                                                                                                                  
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Dockerfile:3
--------------------
   1 |     FROM python:3.11.3 AS base 
   2 |     WORKDIR /app
   3 | >>> RUN echo "deb http://apt.postgresql.org/pub/repos/apt buster-pgdg main" > /etc/apt/sources.list.d/pgdg.list
   4 |     RUN wget --quiet -O - https://www.postgresql.org/media/keys/ACCC4CF8.asc | apt-key add -
   5 |     RUN apt-get update && apt-get install -y postgresql-client-12 graphviz graphviz-dev python3-opencv
--------------------
ERROR: failed to solve: process "/bin/sh -c echo \"deb http://apt.postgresql.org/pub/repos/apt buster-pgdg main\" > /etc/apt/sources.list.d/pgdg.list" 
did not complete successfully: exit code: 1

I'm running Docker 23.0.5 installed from the Docker's Debian repositories.