os/exec: resource leak on exec failure #69284
Description
Go version
go version go1.23.0 linux/amd64
Output of go env in your module/workspace:
GO111MODULE=''
GOARCH='amd64'
GOBIN=''
GOCACHE='/home/user/.cache/go-build'
GOENV='/home/user/.config/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFLAGS=''
GOHOSTARCH='amd64'
GOHOSTOS='linux'
GOINSECURE=''
GOMODCACHE='/home/user/go/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='linux'
GOPATH='/home/user/go'
GOPRIVATE=''
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/usr/local/go'
GOSUMDB='sum.golang.org'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/usr/local/go/pkg/tool/linux_amd64'
GOVCS=''
GOVERSION='go1.23.0'
GODEBUG=''
GOTELEMETRY='local'
GOTELEMETRYDIR='/home/user/.config/go/telemetry'
GCCGO='gccgo'
GOAMD64='v1'
AR='ar'
CC='gcc'
CXX='g++'
CGO_ENABLED='1'
GOMOD='/dev/null'
GOWORK=''
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
PKG_CONFIG='pkg-config'
GOGCCFLAGS='-fPIC -m64 -pthread -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=/tmp/go-build2691713470=/tmp/go-build -gno-record-gcc-switches'What did you do?
It seems that when process.Start fails, there are some files left open, which after a while leads to a "too many open files" error.
Here's a minimal repro:
package main
import (
"context"
"errors"
"os/exec"
"syscall"
"testing"
)
func TestExecResources(t *testing.T) {
ctx := context.Background()
var oldRLimit syscall.Rlimit
err := syscall.Getrlimit(syscall.RLIMIT_NOFILE, &oldRLimit)
if err != nil {
t.Fatal(err)
}
newRLimit := oldRLimit
newRLimit.Cur = 20
err = syscall.Setrlimit(syscall.RLIMIT_NOFILE, &newRLimit)
if err != nil {
t.Fatal(err)
}
defer func() {
syscall.Setrlimit(syscall.RLIMIT_NOFILE, &oldRLimit)
}()
for i := 0; i < 22; i++ {
ctx, cancel := context.WithCancel(ctx)
process := exec.CommandContext(ctx, "/bin/nonexistent")
err = process.Start()
cancel()
process.Wait() // not really needed, just to demonstrate that even calling Wait doesn't help
var se syscall.Errno
if !errors.As(err, &se) || se != syscall.ENOENT {
t.Fatal(err)
}
}
}What did you see happen?
The test fails with:
--- FAIL: TestExecResources (0.00s)
process_unix_test.go:35: fork/exec /bin/nonexistent: too many open files
What did you expect to see?
I expected the test to pass.
Note that the issue occurs also on other exec failures, such as permission denied, invalid ELF format, etc.