cmd/go: go mod creates files with incorrect read-only permissions

[0intro]

What version of Go are you using (go version)?

$ go version
go version devel +498eaee461 Fri Nov 15 02:31:58 2019 +0000 linux/amd64

Does this issue reproduce with the latest release?

No.

What operating system and processor architecture are you using (go env)?

go env Output

$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/djc/.cache/go-build"
GOENV="/home/djc/.config/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/djc/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/linux_amd64"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD=""
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build726010483=/tmp/go-build -gno-record-gcc-switches"

What did you do?

$ mkdir pkg
$ cd pkg
$ go mod init example.com/m
go: creating new go.mod: module example.com/m
$ echo -e 'package pkg\nimport "golang.org/x/image/bmp"' >pkg.go
$ go get ...
go: downloading golang.org/x/image v0.0.0-20191009234506-e7c1f5e7dbb8
go: finding versions for golang.org/x/image/bmp
go: found golang.org/x/image/bmp in golang.org/x/image v0.0.0-20191009234506-e7c1f5e7dbb8
go: downloading golang.org/x/text v0.3.0
go: downloading golang.org/x/tools v0.0.0-20191114222411-4191b8cbba09
go: found golang.org/x/tools/go/buildutil in golang.org/x/tools v0.0.0-20191114222411-4191b8cbba09
go: downloading golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2
go: downloading golang.org/x/net v0.0.0-20190620200207-3b0461eec859
go: downloading golang.org/x/sync v0.0.0-20190423024810-112230192c58
go: downloading golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a
go: downloading golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7
go: golang.org/x/sync upgrade => v0.0.0-20190911185100-cd5d95a43a6e
go: golang.org/x/text upgrade => v0.3.2
go: golang.org/x/sys upgrade => v0.0.0-20191113165036-4c7a9d0fe056
go: golang.org/x/net upgrade => v0.0.0-20191112182307-2180aed22343
go: golang.org/x/crypto upgrade => v0.0.0-20191112222119-e1110fd1c708
go: golang.org/x/xerrors upgrade => v0.0.0-20191011141410-1b5146add898
go: downloading golang.org/x/crypto v0.0.0-20191112222119-e1110fd1c708
go: downloading golang.org/x/net v0.0.0-20191112182307-2180aed22343
go: downloading golang.org/x/sync v0.0.0-20190911185100-cd5d95a43a6e
go: downloading golang.org/x/sys v0.0.0-20191113165036-4c7a9d0fe056
go: downloading golang.org/x/text v0.3.2
go: downloading golang.org/x/xerrors v0.0.0-20191011141410-1b5146add898
# example.com/m
./pkg.go:2:8: imported and not used: "golang.org/x/image/bmp"

The files created by go mod have incorrect 444 (read-only) permissions:

$ ls -l $GOPATH/pkg/mod/golang.org/x/image*
total 96
-r--r--r--. 1 djc djc  173 Nov 15 10:49 AUTHORS
dr-xr-xr-x. 2 djc djc 4096 Nov 15 10:49 bmp
dr-xr-xr-x. 3 djc djc 4096 Nov 15 10:49 ccitt
dr-xr-xr-x. 3 djc djc 4096 Nov 15 10:49 cmd
-r--r--r--. 1 djc djc   21 Nov 15 10:49 codereview.cfg
dr-xr-xr-x. 2 djc djc 4096 Nov 15 10:49 colornames
-r--r--r--. 1 djc djc  913 Nov 15 10:49 CONTRIBUTING.md
-r--r--r--. 1 djc djc  170 Nov 15 10:49 CONTRIBUTORS
dr-xr-xr-x. 2 djc djc 4096 Nov 15 10:49 draw
dr-xr-xr-x. 3 djc djc 4096 Nov 15 10:49 example
dr-xr-xr-x. 9 djc djc 4096 Nov 15 10:49 font
-r--r--r--. 1 djc djc   69 Nov 15 10:49 go.mod
-r--r--r--. 1 djc djc  153 Nov 15 10:49 go.sum
-r--r--r--. 1 djc djc 1479 Nov 15 10:49 LICENSE
dr-xr-xr-x. 5 djc djc 4096 Nov 15 10:49 math
-r--r--r--. 1 djc djc 1303 Nov 15 10:49 PATENTS
-r--r--r--. 1 djc djc  601 Nov 15 10:49 README.md
dr-xr-xr-x. 2 djc djc 4096 Nov 15 10:49 riff
dr-xr-xr-x. 2 djc djc 4096 Nov 15 10:49 testdata
dr-xr-xr-x. 3 djc djc 4096 Nov 15 10:49 tiff
dr-xr-xr-x. 2 djc djc 4096 Nov 15 10:49 vector
dr-xr-xr-x. 2 djc djc 4096 Nov 15 10:49 vp8
dr-xr-xr-x. 2 djc djc 4096 Nov 15 10:49 vp8l
dr-xr-xr-x. 2 djc djc 4096 Nov 15 10:49 webp

Consequently, these files cannot be deleted:

$ rm -rf $GOPATH/pkg/mod
rm: cannot remove '/home/djc/go/pkg/mod/golang.org/x/[email protected]/internal/subtle/aliasing.go': Permission denied
rm: cannot remove '/home/djc/go/pkg/mod/golang.org/x/[email protected]/internal/subtle/aliasing_test.go': Permission denied
rm: cannot remove '/home/djc/go/pkg/mod/golang.org/x/[email protected]/internal/subtle/aliasing_appengine.go': Permission denied
rm: cannot remove '/home/djc/go/pkg/mod/golang.org/x/[email protected]/internal/chacha20/chacha_s390x.s': Permission denied
[...]

With correct permissions, the files can be deleted successfully:

$ find $GOPATH/pkg/mod -exec chmod u+w {} \;
$ rm -rf $GOPATH/pkg/mod
$

What did you expect to see?

The files created by go mod should have correct read-write permissions, so they can be deleted by their owner.

What did you see instead?

The files created by go mod have incorrect read-only permissions, so they can't be deleted.

This may be releated to issue #34634.

[mvdan]

Have you seen earlier issues like #27161 and #31481? This seems to be on purpose.

You can use go clean -modcache to get rid of all those files without chmod shenanigans.

[0intro]

Thanks. That's interesting. I'm experiencing side effects related with this behaviour. I'll investigate.

[0intro]

I'm closing this issue since it seems to be the expected behaviour.