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reflect: slice index out of range #31801

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fraenkel opened this issue May 2, 2019 · 4 comments
Closed

reflect: slice index out of range #31801

fraenkel opened this issue May 2, 2019 · 4 comments
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@fraenkel
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fraenkel commented May 2, 2019

Using go version devel +762953be28 Thu May 2 00:42:51 2019 +0000 linux/amd64

While debugging #31784, I received a panic:

stack 
goroutine 274 [running]:
net/http.init.2.func1(0x0, 0x0, 0x0)
	/home/fraenkel/workspace/go/src/net/http/export_test.go:53 +0x95
net/http.(*Client).do.func1(0xc0001cdef0, 0xc0001cdef8)
	/home/fraenkel/workspace/go/src/net/http/client.go:516 +0x4b
panic(0x8ba1c0, 0xa21df0)
	/home/fraenkel/workspace/go/src/runtime/panic.go:619 +0x1b2
reflect.Value.Index(0x8b3420, 0xc0004a2258, 0x1b7, 0x2e, 0x76, 0x4, 0x1a8)
	/home/fraenkel/workspace/go/src/reflect/value.go:938 +0x1fe
fmt.(*pp).printValue(0xc0003000c0, 0x8b3420, 0xc0004a2258, 0x1b7, 0x76, 0x3)
	/home/fraenkel/workspace/go/src/fmt/print.go:839 +0x87e
fmt.(*pp).printValue(0xc0003000c0, 0x91a7a0, 0xc0004a2258, 0x1b9, 0x76, 0x2)
	/home/fraenkel/workspace/go/src/fmt/print.go:789 +0x1b45
fmt.(*pp).printValue(0xc0003000c0, 0x963aa0, 0xc0004a2000, 0x199, 0xc000000076, 0x1)
	/home/fraenkel/workspace/go/src/fmt/print.go:789 +0x1b45
fmt.(*pp).printValue(0xc0003000c0, 0x960920, 0xc0004a2000, 0x16, 0x76, 0x0)
	/home/fraenkel/workspace/go/src/fmt/print.go:859 +0x194a
fmt.(*pp).printArg(0xc0003000c0, 0x960920, 0xc0004a2000, 0xc000000076)
	/home/fraenkel/workspace/go/src/fmt/print.go:695 +0x2b4
fmt.(*pp).doPrintf(0xc0003000c0, 0x9671df, 0x4, 0xc0001cd668, 0x1, 0x1)
	/home/fraenkel/workspace/go/src/fmt/print.go:1009 +0x15b
fmt.Fprintf(0xa2cb20, 0xc000010018, 0x9671df, 0x4, 0xc0001cd668, 0x1, 0x1, 0x4f9b7e, 0x8e4500, 0xd8ffa0)
	/home/fraenkel/workspace/go/src/fmt/print.go:199 +0x72
fmt.Printf(...)
	/home/fraenkel/workspace/go/src/fmt/print.go:208
net/http_test.TestTransportMaxConnsPerHost.func2.2.1(0xa3d3a0, 0xc0004a2000, 0xd80001, 0x0)
	/home/fraenkel/workspace/go/src/net/http/transport_test.go:625 +0x9f
net/http.http2traceGotConn(0xc000494600, 0xc000480180)
	/home/fraenkel/workspace/go/src/net/http/h2_bundle.go:8995 +0x192
net/http.(*http2Transport).RoundTripOpt(0xc0002dd8c0, 0xc000494600, 0xc000306c00, 0xc000494600, 0x0, 0x0)
	/home/fraenkel/workspace/go/src/net/http/h2_bundle.go:6866 +0x13b
net/http.(*http2Transport).RoundTrip(0xc0002dd8c0, 0xc000494600, 0x0, 0xc000202d60, 0x5)
	/home/fraenkel/workspace/go/src/net/http/h2_bundle.go:6829 +0x3a
net/http.(*Transport).roundTrip(0xc0002c0640, 0xc000494600, 0x0, 0xc000202d76, 0xc000028b20)
	/home/fraenkel/workspace/go/src/net/http/transport.go:511 +0x734
net/http.(*Transport).RoundTrip(0xc0002c0640, 0xc000494600, 0xc0002c0640, 0x0, 0x0)
	/home/fraenkel/workspace/go/src/net/http/roundtrip.go:17 +0x35
net/http.send(0xc000494600, 0xa2c620, 0xc0002c0640, 0x0, 0x0, 0x0, 0xc00013e050, 0x0, 0x1, 0x0)
	/home/fraenkel/workspace/go/src/net/http/client.go:250 +0x4d5
net/http.(*Client).send(0xc000306660, 0xc000494600, 0x0, 0x0, 0x0, 0xc00013e050, 0x0, 0x1, 0xc00016ad98)
	/home/fraenkel/workspace/go/src/net/http/client.go:174 +0xfa
net/http.(*Client).do(0xc000306660, 0xc000494600, 0x0, 0x0, 0x0)
	/home/fraenkel/workspace/go/src/net/http/client.go:641 +0x460
net/http.(*Client).Do(...)
	/home/fraenkel/workspace/go/src/net/http/client.go:509
net/http_test.TestTransportMaxConnsPerHost.func2.2()
	/home/fraenkel/workspace/go/src/net/http/transport_test.go:637 +0x22e
net/http_test.TestTransportMaxConnsPerHost.func2.3(0xc0001b5200, 0xc000306ae0)
	/home/fraenkel/workspace/go/src/net/http/transport_test.go:653 +0x4d
created by net/http_test.TestTransportMaxConnsPerHost.func2
	/home/fraenkel/workspace/go/src/net/http/transport_test.go:651 +0x2be
exit status 2

I added the following line

diff --git a/src/net/http/transport_test.go b/src/net/http/transport_test.go
index 44a935960e..be8420478f 100644
--- a/src/net/http/transport_test.go
+++ b/src/net/http/transport_test.go
@@ -622,6 +622,7 @@ func TestTransportMaxConnsPerHost(t *testing.T) {
                doReq := func() {
                        trace := &httptrace.ClientTrace{
                                GotConn: func(connInfo httptrace.GotConnInfo) {
+                                       fmt.Printf("%#v\n", connInfo.Conn)
                                        if !connInfo.Reused {
                                                atomic.AddInt32(&gotConnCnt, 1)
                                        }

And I am running the following command
go test -test.short=0 -run TestTransportMaxConnsPerHost$ -count=1000 -v > log
@cuonglm
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cuonglm commented May 2, 2019

It's interesting that using %+v does not trigger the panic.

@martisch
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martisch commented May 2, 2019

Running with go test -race -test.short=0 -run TestTransportMaxConnsPerHost$ -count=1000 -v
shows there is a data race for accessing the slice for which the index panics. Likely between fmt checking that index < len and and accesing that index from the slice the slice has been updated.

@martisch martisch closed this as completed May 2, 2019
@zeisss
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zeisss commented Nov 15, 2019 •
edited
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Are any more infos on this available?

We are seeing the same problem when using fmt.Printf() with either %+v and %#v while trying to understand why our HTTP Tracers seem to get a nil connection provided to GotConn(): Calling info.Conn.RemoteAddr() panics with:

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x30 pc=0x492195f]

$ go version
go version go1.13 darwin/amd64

@cuonglm
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cuonglm commented Nov 15, 2019

Are any more infos on this available?

We are seeing the same problem when using fmt.Printf() with either %+v and %#v while trying to understand why our HTTP Tracers seem to get a nil connection provided to GotConn(): Calling info.Conn.RemoteAddr() panics with:

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x30 pc=0x492195f]

$ go version
go version go1.13 darwin/amd64

It's fixed in 1.13.3

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@zeisss @martisch @fraenkel @cuonglm @gopherbot