v0.18.*: "ERROR: failed to solve: exit code: 1" on "syntax=docker/dockerfile:1.7-labs" line of a Dockerfile

[dimikot]

Repro:

docker buildx rm container
docker buildx create --name=container --driver=docker-container --bootstrap
cd ~
mkdir -p test
(echo "# syntax=docker/dockerfile:1.7-labs"; echo "FROM public.ecr.aws/lts/ubuntu:22.04 AS test") > test/Dockerfile
docker buildx build --builder=container --file test/Dockerfile .

Reproducible with --driver-opt="image=moby/buildkit:v0.18.1" and --driver-opt="image=moby/buildkit:v0.18.0". Works fine with --driver-opt="image=moby/buildkit:v0.17.3".

Success on 0.17.3 and failure on 0.18.0:

Failure on 0.18.1:

"docker-ce=5:27.3.1-1~ubuntu.24.04~noble",
"docker-ce-cli=5:27.3.1-1~ubuntu.24.04~noble",
"containerd.io=1.7.23-1",
"docker-compose-plugin=2.29.7-1~ubuntu.24.04~noble",
"docker-buildx-plugin=0.17.1-1~ubuntu.24.04~noble",

And also sysbox:
https://downloads.nestybox.com/sysbox/releases/v0.6.4/sysbox-ce_0.6.4-0.linux_$(dpkg --print-architecture).deb

$ cat /etc/os-release
PRETTY_NAME="Ubuntu 24.04.1 LTS"
NAME="Ubuntu"
VERSION_ID="24.04"
VERSION="24.04.1 LTS (Noble Numbat)"
VERSION_CODENAME=noble
ID=ubuntu
ID_LIKE=debian

[tonistiigi]

I tested the provided steps locally and in Github codespaces and didn't reproduce in either.

@crazy-max Can you confirm?

@dimikot You could try with --buildkitd-flags '--debug' and see if there is anything interesting in daemon logs.