os: MkdirAll fails if permissions do not include execute for owner

[zwass]

Please answer these questions before submitting your issue. Thanks!

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

go version go1.9.1 darwin/amd64

Does this issue reproduce with the latest release?

Yes

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

GOARCH="amd64"
GOBIN=""
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH="/Users/zwass/dev/go"
GORACE=""
GOROOT="/usr/local/Cellar/go/1.9.1/libexec"
GOTOOLDIR="/usr/local/Cellar/go/1.9.1/libexec/pkg/tool/darwin_amd64"
GCCGO="gccgo"
CC="clang"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/4k/2q3ctn7d5_xb03_zsb3v6lgr0000gn/T/go-build972837205=/tmp/go-build -gno-record-gcc-switches -fno-common"
CXX="clang++"
CGO_ENABLED="1"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"

What did you do?

package main

import (
	"fmt"
	"os"
)

func main() {
	fmt.Println(os.MkdirAll("foo/bar", 0644))
}

What did you expect to see?

No error. Directories are created with the provided permission bits (modified by umask).

Or, following the rules as described for mkdir -p:

Intermediate directories are created with permission bits of rwxrwxrwx (0777) as modified by the current umask, plus write and search permission for the owner.

What did you see instead?

mkdir foo/bar: permission denied

The directory foo is created (with perms as expected after including umask), but the directory foo/bar is not.

[robpike]

It's doing exactly what the documentation says it does. I don't believe this is a bug. A change like this is a feature request but I'm not sure it should be done as it is considerably more complex and racy to do what is asked than to do what is specified.

[rsc]

mkdir(1) documents that the -m mode applies only to the final created directory, while os.MkdirAll documents that the permission bits apply to all directories. I don't believe we can change either one to bring them in line with each other at this point. It's unfortunate, but easy to work around: allow at least the 0700 bits, or use an os.MkdirAll for the parent followed by an os.Mkdir with mode 0 for the final element.