x/net/http2/h2c panic

[chenjie199234]

Go version

Go Version:1.22.2
build host:windows/amd64
build target:linux/amd64
run host:linux/amd64

Output of go env in your module/workspace:

set GO111MODULE=
set GOARCH=amd64
go: stripping unprintable or unescapable characters from %"GOBIN"%
set GOBIN=C:\Users\������\Desktop\Go\bin
go: stripping unprintable or unescapable characters from %"GOCACHE"%
set GOCACHE=C:\Users\������\Desktop\Go\cache
go: stripping unprintable or unescapable characters from %"GOENV"%
set GOENV=C:\Users\������\AppData\Roaming\go\env
set GOEXE=.exe
set GOEXPERIMENT=
set GOFLAGS=
set GOHOSTARCH=amd64
set GOHOSTOS=windows
set GOINSECURE=
go: stripping unprintable or unescapable characters from %"GOMODCACHE"%
set GOMODCACHE=C:\Users\������\Desktop\Go\pkg\mod
set GONOPROXY=
set GONOSUMDB=
set GOOS=windows
go: stripping unprintable or unescapable characters from %"GOPATH"%
set GOPATH=C:\Users\������\Desktop\Go
set GOPRIVATE=
set GOPROXY=direct
set GOROOT=C:\Program Files\Go
set GOSUMDB=off
set GOTMPDIR=
set GOTOOLCHAIN=auto
set GOTOOLDIR=C:\Program Files\Go\pkg\tool\windows_amd64
set GOVCS=
set GOVERSION=go1.22.2
set GCCGO=gccgo
set GOAMD64=v1
set AR=ar
set CC=gcc
set CXX=g++
set CGO_ENABLED=0
set GOMOD=NUL
set GOWORK=
set CGO_CFLAGS=-O2 -g
set CGO_CPPFLAGS=
set CGO_CXXFLAGS=-O2 -g
set CGO_FFLAGS=-O2 -g
set CGO_LDFLAGS=-O2 -g
set PKG_CONFIG=pkg-config
go: stripping unprintable or unescapable characters from %"GOGCCFLAGS"%
set GOGCCFLAGS=-m64 -fno-caret-diagnostics -Qunused-arguments -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=C:\Users\������\AppData\Local\Temp\go-build1138275416=/tmp/go-build -gno-record-gcc-switches

What did you do?

use x/net/h2c to start a h2c http server

h2c.NewHandler(r, &http2.Server{
	NewWriteScheduler:         func() http2.WriteScheduler { return http2.NewPriorityWriteScheduler(nil) },
	IdleTimeout:               time.Second * 5,
	MaxDecoderHeaderTableSize: 2048,
	MaxEncoderHeaderTableSize: 2048,
})

What did you see happen?

http: panic serving xxx.xxx.xxx.xxx:xxx: runtime error: invalid memory address or nil pointer dereference
goroutine 1028135 [running]:
net/http.(*conn).serve.func1()
	C:/Program Files/Go/src/net/http/server.go:1898 +0xbe
panic({0x1a14840?, 0x2dc6780?})
	C:/Program Files/Go/src/runtime/panic.go:770 +0x132
time.(*Timer).Reset(0x1a06a40?, 0xc00024dc50?)
	C:/Program Files/Go/src/time/sleep.go:135 +0xe
golang.org/x/net/http2.(*serverConn).closeStream(0xc00033ed00, 0xc0004d43c0, {0x1f847e0, 0x2dc8b20})
	C:/Users/陈杰/Desktop/Go/pkg/mod/golang.org/x/net@v0.24.0/http2/server.go:1642 +0x17b
golang.org/x/net/http2.(*serverConn).closeAllStreamsOnConnClose(0xc00033ed00)
	C:/Users/陈杰/Desktop/Go/pkg/mod/golang.org/x/net@v0.24.0/http2/server.go:862 +0xaa
golang.org/x/net/http2.(*serverConn).serve(0xc00033ed00)
	C:/Users/陈杰/Desktop/Go/pkg/mod/golang.org/x/net@v0.24.0/http2/server.go:919 +0x6ea
golang.org/x/net/http2.(*Server).ServeConn(0xc0004e2be0, {0x1fa57b0, 0xc0003c8018}, 0xc0005239b0)
	C:/Users/陈杰/Desktop/Go/pkg/mod/golang.org/x/net@v0.24.0/http2/server.go:532 +0xbad
golang.org/x/net/http2/h2c.h2cHandler.ServeHTTP({{0x1f85380?, 0xc0002513e0?}, 0xc0004e2be0?}, {0x1f92380, 0xc000134620}, 0xc0001c0240)
	C:/Users/陈杰/Desktop/Go/pkg/mod/golang.org/x/net@v0.24.0/http2/h2c/h2c.go:116 +0x649
net/http.serverHandler.ServeHTTP({0xc00024dad0?}, {0x1f92380?, 0xc000134620?}, 0x6?)
	C:/Program Files/Go/src/net/http/server.go:3137 +0x8e
net/http.(*conn).serve(0xc00015ee10, {0x1f9f2a0, 0xc00024da70})
	C:/Program Files/Go/src/net/http/server.go:2039 +0x5e8
created by net/http.(*Server).Serve in goroutine 58
	C:/Program Files/Go/src/net/http/server.go:3285 +0x4b4

What did you expect to see?

no panic

[seankhliao]

do you have a way to reproduce this?

[chenjie199234]

@seankhliao i don't think we nee a reproduce.
follow the panic stack info,we can find the reason.

we create a Conn here:
https://github.com/golang/net/blob/b20cd5933aa9ba90f6299e6c2cbb59733434636e/http2/server.go#L402
then we serve the conn here:
https://github.com/golang/net/blob/b20cd5933aa9ba90f6299e6c2cbb59733434636e/http2/server.go#L888
we setted idletimeout,so it will be inited here:
https://github.com/golang/net/blob/b20cd5933aa9ba90f6299e6c2cbb59733434636e/http2/server.go#L928
but the conn returned before the idletimer be inited at here:
https://github.com/golang/net/blob/b20cd5933aa9ba90f6299e6c2cbb59733434636e/http2/server.go#L917
so the idletimer is nil now!
when the conn is closing,we will go into here:
https://github.com/golang/net/blob/b20cd5933aa9ba90f6299e6c2cbb59733434636e/http2/server.go#L892
and we will close all the streams here:
https://github.com/golang/net/blob/b20cd5933aa9ba90f6299e6c2cbb59733434636e/http2/server.go#L862
the stream will be deleted from the conn here:
https://github.com/golang/net/blob/b20cd5933aa9ba90f6299e6c2cbb59733434636e/http2/server.go#L1643
when last stream be deleted(in this case we only have 1 stream,the not prepared one):
https://github.com/golang/net/blob/b20cd5933aa9ba90f6299e6c2cbb59733434636e/http2/server.go#L1643
then the code trying to close the idletimer but the idletimer is not inited,it is nil:
https://github.com/golang/net/blob/b20cd5933aa9ba90f6299e6c2cbb59733434636e/http2/server.go#L1647

we need to add a nil check before close it

[gopherbot]

Change https://go.dev/cl/584255 mentions this issue: http2: avoid panic on h2c upgrade failure