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runtime: "fatal error: unexpected signal" 0xC0000005 on Windows during string operations #46148

yusufozturk opened this issue May 13, 2021 · 3 comments


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@yusufozturk yusufozturk commented May 13, 2021

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

$ go version
go version go1.16.4 windows/amd64

Does this issue reproduce with the latest release?


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

go env Output
$ go env
set GO111MODULE=
set GOARCH=amd64
set GOBIN=
set GOCACHE=C:\Users\Administrator\AppData\Local\go-build
set GOENV=C:\Users\Administrator\AppData\Roaming\go\env
set GOEXE=.exe
set GOHOSTARCH=amd64
set GOHOSTOS=windows
set GOMODCACHE=C:\Users\Administrator\go\pkg\mod
set GOOS=windows
set GOPATH=C:\Users\Administrator\go
set GOPROXY=,direct
set GOROOT=C:\Program Files\Go
set GOTOOLDIR=C:\Program Files\Go\pkg\tool\windows_amd64
set GOVCS=
set GOVERSION=go1.16.4
set GCCGO=gccgo
set AR=ar
set CC=gcc
set CXX=g++
set GOMOD=C:\Repos\\VirtualMetric\virtualmetric-go\go.mod
set CGO_CFLAGS=-g -O2
set CGO_FFLAGS=-g -O2
set CGO_LDFLAGS=-g -O2
set PKG_CONFIG=pkg-config
set GOGCCFLAGS=-m64 -mthreads -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=C:\Users\ADMINI~1\AppData\Local\Temp\2\go-build2746031420=/tmp/go-build -gno-record-gcc-switches

What did you do?

Our app makes many syscalls to collect different data for forensic analysis. Everytime when we got panic, it always happens in string operations (usually strconv.Itoa()) and always in "Remote Connection" analysis to detect remote attackers to pc. So right now, we disabled the remote connection analysis and we will test it. This issue usually happens after 12-24 hours. If issue would not happen, we will activate the remote connection analysis and disable Windows Defender to find out if Defender somehow crashing the app. App uses around 30-50 mb memory and there is always around 6 gb of free memory on the machine. Machine is running in Hyper-V virtualization as a VM. There is no dynamic memory or ballooning. All resources are allocated just for this VM. Here is where the issue happens:

// Remote Connection
remoteConn := model.HostRemoteConnection{
	SessionName:   "console-" + strconv.Itoa(session.Session),
	SessionID:     session.Session,
	Type:          session.Type,
	RemoteAddress: session.RemoteAddress,
	LocalPort:     session.LocalPort,
	Username:      session.Username,
	State:         session.State,
	CreationTime:  session.LogonTime,

strconv.Itoa(session.Session) panics.

What did you expect to see?

I would expect not to see any issue during the string operation or get an error in return.

What did you see instead?

fatal error: unexpected signal during runtime execution
[signal 0xc0000005 code=0x1 addr=0xc00110b4d0 pc=0x103e77a]

goroutine 16 [running]:
runtime.throw(0x1a2250c, 0x2a)
        C:/Program Files/Go/src/runtime/panic.go:1117 +0x79 fp=0xc0002993c8 sp=0xc000299398 pc=0x106c3b9
        C:/Program Files/Go/src/runtime/signal_windows.go:233 +0x317 fp=0xc000299420 sp=0xc0002993c8 pc=0x10823b7
runtime.mallocgc(0x9, 0x0, 0x2002d00, 0x1c1daaa0000)
        C:/Program Files/Go/src/runtime/malloc.go:1048 +0x33a fp=0xc0002994a8 sp=0xc000299420 pc=0x103e77a
runtime.rawstring(0x9, 0x0, 0x0, 0x0, 0x0, 0x0)
        C:/Program Files/Go/src/runtime/string.go:263 +0x56 fp=0xc0002994d8 sp=0xc0002994a8 pc=0x1087396
runtime.rawstringtmp(0x0, 0x9, 0x1082898, 0x0, 0x0, 0xc000299590, 0x10f4b38)
        C:/Program Files/Go/src/runtime/string.go:131 +0x7c fp=0xc000299518 sp=0xc0002994d8 pc=0x1086d3c
runtime.concatstrings(0x0, 0xc0002995f8, 0x2, 0x2, 0x1b2eec0, 0x2002de0)
        C:/Program Files/Go/src/runtime/string.go:50 +0xc5 fp=0xc0002995b0 sp=0xc000299518 pc=0x1086785
runtime.concatstring2(0x0, 0x1a02bc1, 0x8, 0x1a1d12a, 0x1, 0x0, 0x0)
        C:/Program Files/Go/src/runtime/string.go:59 +0x4e fp=0xc0002995f0 sp=0xc0002995b0 pc=0x1086a0e, 0x1, 0x1, 0xc000299940, 0x0, 0x0, 0xc0002999c0)
        C:/Repos/ +0x13f fp=0xc000299848 sp=0xc0002995f0 pc=0x163b2ff, 0xc000366b40, 0xc000938060)
        C:/Repos/ +0xfcd fp=0xc000299d88 sp=0xc000299848 pc=0x163a48d*remoteconnection).collect(0x208fd78, 0xc000029600, 0xc000366b40, 0xc000938060)
        :1 +0x57 fp=0xc000299db0 sp=0xc000299d88 pc=0x1651917, 0xc000366b40, 0x0, 0x0)
        C:/Repos/ +0xf1 fp=0xc000299e20 sp=0xc000299db0 pc=0x1632d71
        C:/Repos/*IIntegration).CollectEvent(0x208fd78, 0xc000029600, 0xc000366b40, 0xc000e84000, 0x18c2960)
        :1 +0x4d fp=0xc000299e50 sp=0xc000299e20 pc=0x16bcded, 0xc000366b40)
        C:/Repos/ +0x92 fp=0xc000299ec0 sp=0xc000299e50 pc=0x1845412, 0xc000366b40, 0xc00033d7a0, 0xc000302a80)
        C:/Repos/ +0x2b4 fp=0xc000299f88 sp=0xc000299ec0 pc=0x18450d4*event).startCollector(0x208fd78, 0xc000029600, 0xc000366b40, 0xc00033d7a0, 0xc000302a80)
        :1 +0x65 fp=0xc000299fb8 sp=0xc000299f88 pc=0x1849f05
        C:/Program Files/Go/src/runtime/asm_amd64.s:1371 +0x1 fp=0xc000299fc0 sp=0xc000299fb8 pc=0x10a5361
created by
        C:/Repos/ +0x1a9
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@davecheney davecheney commented May 13, 2021

Thank you for raising this issue. You mentioned that this issue occurs using strconv but the stack trace you supplied does not appear to include strconv.

This may be memory corruption. Have you tried running your program under the race detector? See .


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@yusufozturk yusufozturk commented May 13, 2021

Thank you so much for your reply @davecheney

We started the app with race detector and there are many issues and now we are solving them. I have one question about the race issues. Do you think memory corruption might happen after many data race issues? I see them in the race detector but app runs without issue. But I understand that, at some point, it will corrupt the memory?

App is still being in the test. If the panic happens, I will also share the latest data race issue.


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@heschi heschi commented May 13, 2021

Hi there,

Unlike many projects, the Go project does not use GitHub Issues for general discussion or asking questions. GitHub Issues are used for tracking bugs and proposals only.

For asking questions, see:

Please ask the question on one of the above forums.

(Quoted from


@heschi heschi closed this May 13, 2021
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3 participants