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cmd/compile: panic during late opt while compiling (*ecdheKeyAgreement).processServerKeyExchange #27142

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mvdan opened this issue Aug 22, 2018 · 4 comments
Closed

cmd/compile: panic during late opt while compiling (*ecdheKeyAgreement).processServerKeyExchange #27142

mvdan opened this issue Aug 22, 2018 · 4 comments
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@mvdan
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mvdan commented Aug 22, 2018

darwin-amd64-race at 64f3d75

https://build.golang.org/log/c2d6822a46b0e167cd2514e8553270f2a916ffcc

# crypto/tls [crypto/tls.test]
/var/folders/dx/k53rs1s93538b4x20g46cj_w0000gn/T/workdir/go/src/crypto/tls/key_agreement.go:292:20: internal compiler error: '(*ecdheKeyAgreement).processServerKeyExchange': panic during late opt while compiling (*ecdheKeyAgreement).processServerKeyExchange:

runtime error: invalid memory address or nil pointer dereference

goroutine 1 [running]:
cmd/compile/internal/ssa.Compile.func1(0xc001a1ea28, 0xc0015c2000)
	/private/var/folders/dx/k53rs1s93538b4x20g46cj_w0000gn/T/workdir/go/src/cmd/compile/internal/ssa/compile.go:38 +0xc6
panic(0x184a0a0, 0x1eefa20)
	/private/var/folders/dx/k53rs1s93538b4x20g46cj_w0000gn/T/workdir/go/src/runtime/panic.go:513 +0x1b9
cmd/compile/internal/ssa.rewriteValuegeneric_OpNeq64_0(0xc00134ab30, 0x30)
	/private/var/folders/dx/k53rs1s93538b4x20g46cj_w0000gn/T/workdir/go/src/cmd/compile/internal/ssa/rewritegeneric.go:20251 +0x742
cmd/compile/internal/ssa.rewriteValuegeneric(0xc00134ab30, 0x0)
	/private/var/folders/dx/k53rs1s93538b4x20g46cj_w0000gn/T/workdir/go/src/cmd/compile/internal/ssa/rewritegeneric.go:293 +0x15a3
cmd/compile/internal/ssa.applyRewrite(0xc0015c2000, 0x18c8150, 0x18c81b0)
	/private/var/folders/dx/k53rs1s93538b4x20g46cj_w0000gn/T/workdir/go/src/cmd/compile/internal/ssa/rewrite.go:78 +0x351
cmd/compile/internal/ssa.opt(0xc0015c2000)
	/private/var/folders/dx/k53rs1s93538b4x20g46cj_w0000gn/T/workdir/go/src/cmd/compile/internal/ssa/opt.go:9 +0x43
cmd/compile/internal/ssa.Compile(0xc0015c2000)
	/private/var/folders/dx/k53rs1s93538b4x20g46cj_w0000gn/T/workdir/go/src/cmd/compile/internal/ssa/compile.go:70 +0x30e
cmd/compile/internal/gc.buildssa(0xc0009e2b00, 0x0, 0x0)
	/private/var/folders/dx/k53rs1s93538b4x20g46cj_w0000gn/T/workdir/go/src/cmd/compile/internal/gc/ssa.go:212 +0xab0
cmd/compile/internal/gc.compileSSA(0xc0009e2b00, 0x0)
	/private/var/folders/dx/k53rs1s93538b4x20g46cj_w0000gn/T/workdir/go/src/cmd/compile/internal/gc/pgen.go:259 +0x39
cmd/compile/internal/gc.compile(0xc0009e2b00)
	/private/var/folders/dx/k53rs1s93538b4x20g46cj_w0000gn/T/workdir/go/src/cmd/compile/internal/gc/pgen.go:238 +0x1a0
cmd/compile/internal/gc.funccompile(0xc0009e2b00)
	/private/var/folders/dx/k53rs1s93538b4x20g46cj_w0000gn/T/workdir/go/src/cmd/compile/internal/gc/pgen.go:209 +0xbd
cmd/compile/internal/gc.Main(0x18c7b00)
	/private/var/folders/dx/k53rs1s93538b4x20g46cj_w0000gn/T/workdir/go/src/cmd/compile/internal/gc/main.go:641 +0x2670
main.main()
	/private/var/folders/dx/k53rs1s93538b4x20g46cj_w0000gn/T/workdir/go/src/cmd/compile/main.go:51 +0x96



goroutine 1 [running]:
runtime/debug.Stack(0x0, 0x0, 0x0)
	/private/var/folders/dx/k53rs1s93538b4x20g46cj_w0000gn/T/workdir/go/src/runtime/debug/stack.go:24 +0xa7
cmd/compile/internal/gc.Fatalf(0xc0006b8340, 0x32, 0xc0003c5590, 0x5, 0x5)
	/private/var/folders/dx/k53rs1s93538b4x20g46cj_w0000gn/T/workdir/go/src/cmd/compile/internal/gc/subr.go:182 +0x1f7
cmd/compile/internal/gc.(*ssafn).Fatalf(0xc0014c6c90, 0x1241400000000a, 0x18bf0d0, 0x2c, 0xc00176fc00, 0x4, 0x4)
	/private/var/folders/dx/k53rs1s93538b4x20g46cj_w0000gn/T/workdir/go/src/cmd/compile/internal/gc/ssa.go:5606 +0x1dd
cmd/compile/internal/ssa.(*Func).Fatalf(0xc0015c2000, 0x18bf0d0, 0x2c, 0xc00176fc00, 0x4, 0x4)
	/private/var/folders/dx/k53rs1s93538b4x20g46cj_w0000gn/T/workdir/go/src/cmd/compile/internal/ssa/func.go:575 +0x73
cmd/compile/internal/ssa.Compile.func1(0xc001a1ea28, 0xc0015c2000)
	/private/var/folders/dx/k53rs1s93538b4x20g46cj_w0000gn/T/workdir/go/src/cmd/compile/internal/ssa/compile.go:40 +0x23a
panic(0x184a0a0, 0x1eefa20)
	/private/var/folders/dx/k53rs1s93538b4x20g46cj_w0000gn/T/workdir/go/src/runtime/panic.go:513 +0x1b9
cmd/compile/internal/ssa.rewriteValuegeneric_OpNeq64_0(0xc00134ab30, 0x30)
	/private/var/folders/dx/k53rs1s93538b4x20g46cj_w0000gn/T/workdir/go/src/cmd/compile/internal/ssa/rewritegeneric.go:20251 +0x742
cmd/compile/internal/ssa.rewriteValuegeneric(0xc00134ab30, 0x0)
	/private/var/folders/dx/k53rs1s93538b4x20g46cj_w0000gn/T/workdir/go/src/cmd/compile/internal/ssa/rewritegeneric.go:293 +0x15a3
cmd/compile/internal/ssa.applyRewrite(0xc0015c2000, 0x18c8150, 0x18c81b0)
	/private/var/folders/dx/k53rs1s93538b4x20g46cj_w0000gn/T/workdir/go/src/cmd/compile/internal/ssa/rewrite.go:78 +0x351
cmd/compile/internal/ssa.opt(0xc0015c2000)
	/private/var/folders/dx/k53rs1s93538b4x20g46cj_w0000gn/T/workdir/go/src/cmd/compile/internal/ssa/opt.go:9 +0x43
cmd/compile/internal/ssa.Compile(0xc0015c2000)
	/private/var/folders/dx/k53rs1s93538b4x20g46cj_w0000gn/T/workdir/go/src/cmd/compile/internal/ssa/compile.go:70 +0x30e
cmd/compile/internal/gc.buildssa(0xc0009e2b00, 0x0, 0x0)
	/private/var/folders/dx/k53rs1s93538b4x20g46cj_w0000gn/T/workdir/go/src/cmd/compile/internal/gc/ssa.go:212 +0xab0
cmd/compile/internal/gc.compileSSA(0xc0009e2b00, 0x0)
	/private/var/folders/dx/k53rs1s93538b4x20g46cj_w0000gn/T/workdir/go/src/cmd/compile/internal/gc/pgen.go:259 +0x39
cmd/compile/internal/gc.compile(0xc0009e2b00)
	/private/var/folders/dx/k53rs1s93538b4x20g46cj_w0000gn/T/workdir/go/src/cmd/compile/internal/gc/pgen.go:238 +0x1a0
cmd/compile/internal/gc.funccompile(0xc0009e2b00)
	/private/var/folders/dx/k53rs1s93538b4x20g46cj_w0000gn/T/workdir/go/src/cmd/compile/internal/gc/pgen.go:209 +0xbd
cmd/compile/internal/gc.Main(0x18c7b00)
	/private/var/folders/dx/k53rs1s93538b4x20g46cj_w0000gn/T/workdir/go/src/cmd/compile/internal/gc/main.go:641 +0x2670
main.main()
	/private/var/folders/dx/k53rs1s93538b4x20g46cj_w0000gn/T/workdir/go/src/cmd/compile/main.go:51 +0x96

FAIL	crypto/tls [build failed]

Seems to be a spurious failure, as the darwin-amd64-race builder column is mostly green.

cc @randall77

This reminds me - https://dev.golang.org/owners/ needs a distinction as to who owns cmd/compile/internal/gc and cmd/compile/internal/ssa.
@mvdan mvdan added the NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. label Aug 22, 2018
@mvdan mvdan added this to the Go1.12 milestone Aug 22, 2018
@mvdan
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mvdan commented Sep 5, 2018

Another one, this time on linux-mipsle. This seems to affect multiple or all environments.

@mvdan mvdan mentioned this issue Sep 14, 2018
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@randall77
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The testfloat failure is unrelated.

I'm confused by the error report. I synced to 64f3d75 and built the compiler on darwin/amd64. The fault location cmd/compile/internal/ssa/rewritegeneric.go:20251 +0x742 is in the middle of an instruction, which doesn't make much sense. Unfortunately the report doesn't have the address that was faulted on.

00000000016039f0 <cmd/compile/internal/ssa.rewriteValuegeneric_OpNeq64_0>:
...
 1604128:       c6 84 24 e8 00 00 00    movb   $0x1,0xe8(%rsp)
 160412f:       01 
 1604130:       48 8b ac 24 d0 00 00    mov    0xd0(%rsp),%rbp
 1604137:       00 
 1604138:       48 81 c4 d8 00 00 00    add    $0xd8,%rsp
 160413f:       c3                      retq

0x16039f0+0x742 = 0x1604132.
If you decode the instruction starting at 0x1604132, it is an instruction that could fault:

lods   %ds:(%rsi),%al

Maybe the pc is being corrupted and happens to land here? Seems unlikely, as the rest of the stack trace looks correct.

@odeke-em
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@randall77 unfortunately from the stack-trace, examining the source code doesn't make sense either on 64f3d75 or perhaps that's due to using -race?

Firstly:

crypto/tls/key_agreement.go:292:20

go/src/crypto/tls/key_agreement.go

Line 292 in 64f3d75

if len(skx.key) < 4 {

and then when rewriting the value using rewriteValueGeneric

go/src/cmd/compile/internal/ssa/rewrite.go

Line 78 in 64f3d75

if rv(v) {

go/src/cmd/compile/internal/ssa/rewritegeneric.go

Line 293 in 64f3d75

return rewriteValuegeneric_OpNeq64_0(v)

go/src/cmd/compile/internal/ssa/rewritegeneric.go

Line 20251 in 64f3d75

return true

all don't seem to be invoking anything that can panic. Perhaps some ideas on why this looks skewed?

@andybons andybons modified the milestones: Go1.12, Go1.13 Feb 12, 2019
@andybons andybons modified the milestones: Go1.13, Go1.14 Jul 8, 2019
@rsc rsc modified the milestones: Go1.14, Backlog Oct 9, 2019
@mvdan
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mvdan commented Oct 28, 2020

We haven't seen this in two years, so I think it's safe to close for now. We can always reopen if it shows up again.

@mvdan mvdan closed this as completed Oct 28, 2020
@golang golang locked and limited conversation to collaborators Oct 28, 2021
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