runtime: kevent on fd 0 failed with 9 fatal error: runtime: netpoll failed

[ericlagergren]

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

$ go version
go version go1.17 darwin/arm64

Does this issue reproduce with the latest release?

Yes, also reproduced it with Go 1.17.1.

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

$ uname -a
Darwin Erics-MacBook-Air.local 20.6.0 Darwin Kernel Version 20.6.0: Wed Jun 23 00:26:27 PDT 2021; root:xnu-7195.141.2~5/RELEASE_ARM64_T8101 arm64

go env Output

$ go env
GO111MODULE=""
GOARCH="arm64"
GOBIN="/Users/eric/gopath/bin"
GOCACHE="/Users/eric/Library/Caches/go-build"
GOENV="/Users/eric/Library/Application Support/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="arm64"
GOHOSTOS="darwin"
GOINSECURE=""
GOMODCACHE="/Users/eric/gopath/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="darwin"
GOPATH="/Users/eric/gopath"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/darwin_arm64"
GOVCS=""
GOVERSION="go1.17"
GCCGO="gccgo"
AR="ar"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD="/Users/eric/git/lwcrypto/go.mod"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -arch arm64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/2f/2_yz21b92h94_pvr2m00gzh80000gn/T/go-build2146294539=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

I was benchmarking some C code to compare it against existing Go code. I haven't had a chance to try and get a working minimal repro yet, but: https://play.golang.org/p/GBK19-dOhsv

What did you expect to see?

Anything other than a crash.

What did you see instead?

A crash.

$ go test -v -vet all -failfast -bench .
=== RUN   TestVectors128a
runtime: kevent on fd 0 failed with 9
fatal error: runtime: netpoll failed

runtime stack:
runtime.throw({0x100faa6f7, 0x17})
	/usr/local/go/src/runtime/panic.go:1198 +0x54
runtime.netpoll(0x8bb2c8de54)
	/usr/local/go/src/runtime/netpoll_kqueue.go:132 +0x378
runtime.findrunnable()
	/usr/local/go/src/runtime/proc.go:2947 +0x72c
runtime.schedule()
	/usr/local/go/src/runtime/proc.go:3367 +0x27c
runtime.park_m(0x14000001520)
	/usr/local/go/src/runtime/proc.go:3516 +0x188
runtime.mcall()
	/usr/local/go/src/runtime/asm_arm64.s:179 +0x54

goroutine 1 [chan receive]:
testing.(*T).Run(0x14000087040, {0x100fa8548, 0xf}, 0x100ff9a28)
	/usr/local/go/src/testing/testing.go:1307 +0x344
testing.runTests.func1(0x14000087040)
	/usr/local/go/src/testing/testing.go:1598 +0x80
testing.tRunner(0x14000087040, 0x140000b3d18)
	/usr/local/go/src/testing/testing.go:1259 +0x104
testing.runTests(0x140000ac030, {0x1010a57b0, 0x1, 0x1}, {0xc046da4720722ae8, 0x8bb2d2ade4, 0x1010ad680})
	/usr/local/go/src/testing/testing.go:1596 +0x3ec
testing.(*M).Run(0x140000ce000)
	/usr/local/go/src/testing/testing.go:1504 +0x4fc
main.main()
	_testmain.go:51 +0x17c

goroutine 19 [runnable]:
strconv.genericFtoa({0x1400009b588, 0x1, 0x44}, 0x3f11e42e12620254, 0x66, 0x2, 0x40)
	/usr/local/go/src/strconv/ftoa.go:57
strconv.AppendFloat(...)
	/usr/local/go/src/strconv/ftoa.go:54
fmt.(*fmt).fmtFloat(0x1400009b560, 0x3f11e42e12620254, 0x40, 0x66, 0x6)
	/usr/local/go/src/fmt/format.go:496 +0x78
fmt.(*pp).fmtFloat(0x1400009b520, 0x3f11e42e12620254, 0x40, 0x66)
	/usr/local/go/src/fmt/print.go:408 +0xd4
fmt.(*pp).printArg(0x1400009b520, {0x100fdb5e0, 0x140000a2088}, 0x66)
	/usr/local/go/src/fmt/print.go:666 +0x25c
fmt.(*pp).doPrintf(0x1400009b520, {0x100fa671d, 0x5}, {0x14000050dc8, 0x1, 0x1})
	/usr/local/go/src/fmt/print.go:1122 +0x798
fmt.Sprintf({0x100fa671d, 0x5}, {0x14000050dc8, 0x1, 0x1})
	/usr/local/go/src/fmt/print.go:219 +0x54
testing.fmtDuration(0x10a9a)
	/usr/local/go/src/testing/testing.go:632 +0xb0
testing.(*T).report(0x140000871e0)
	/usr/local/go/src/testing/testing.go:1525 +0x34
testing.tRunner.func1(0x140000871e0)
	/usr/local/go/src/testing/testing.go:1242 +0x31c
testing.tRunner(0x140000871e0, 0x100ff9a28)
	/usr/local/go/src/testing/testing.go:1265 +0x148
created by testing.(*T).Run
	/usr/local/go/src/testing/testing.go:1306 +0x328
exit status 2
FAIL	github.com/ericlagergren/lwcrypto/ascon/ctest	0.169s

[ericlagergren]

For some reason, the call to Scan in readVecs always returns false. Moving vectors_128a.txt into the current directory (or ./testdata/, etc.) doesn't change anything.

Identical code that does not use cgo does not crash.

The code runs clean with -race.

[thanm]

@ericlagergren thanks for the report. Would you kindly update your example so that it is buildable/runnable?

[ianlancetaylor]

Error 9 is EBADF. The error message reporting fd 0 is weird. That suggests that the program is being invoked with standard input closed. I don't see how that could happen. Still, it should work. My first guess, without looking at the code at all, is that something in the C code is doing a dup2 to put something at descriptor 0, not realizing that that is closing the kqueue descriptor. Or, something in the C code is zeroing out memory such that the runtime variable is being clobbered to 0.

[ericlagergren]

@thanm yeah, I've uploaded it here: https://github.com/ericlagergren/lwcrypto/tree/issue48310

git clone https://github.com/ericlagergren/lwcrypto.git
git checkout issue48310
cd ascon/ctest
go test -v

[ericlagergren]

@ianlancetaylor the C code does not call dup2. It also isn't even running by the time the crash happens.

[ericlagergren]

Can repro with Go 1.16.7. Can't test with Go 1.15.x because there isn't a darwin/arm64 binary release for Go 1.15.x.

[ericlagergren]

Oh. You know what it is? I have a C function named open. Different signature, but same name as open(2). Changing the name fixes the problem.

[ianlancetaylor]

Great, thanks for following up.