runtime: SIGSEGV in (*mheap).alloc via mallocgc

[bcmills]

2021-01-21T20:47:45-e2b4f1f/linux-mips64le-mengzhuo

fatal error: unexpected signal during runtime execution
[signal SIGSEGV: segmentation violation code=0x80 addr=0x0 pc=0x120077080]

runtime stack:
runtime.throw(0x120686749, 0x2a)
	/tmp/farm/go/src/runtime/panic.go:1112 +0x6c
runtime.sigpanic()
	/tmp/farm/go/src/runtime/signal_unix.go:714 +0x3fc
runtime.(*mheap).alloc.func1()
	/tmp/farm/go/src/runtime/mheap.go:904 +0x8
runtime.systemstack(0x0)
	/tmp/farm/go/src/runtime/asm_mips64x.s:206 +0xa8
runtime.mstart()
	/tmp/farm/go/src/runtime/proc.go:1244

goroutine 1652 [running]:
runtime.systemstack_switch()
	/tmp/farm/go/src/runtime/asm_mips64x.s:158 +0x8 fp=0xc000052a80 sp=0xc000052a78 pc=0x12007ea10
runtime.(*mheap).alloc(0x120a14ea0, 0x1, 0x12000010b, 0x12001deac)
	/tmp/farm/go/src/runtime/mheap.go:904 +0x80 fp=0xc000052ac8 sp=0xc000052a80 pc=0x120030ce8
runtime.(*mcentral).grow(0x120a25918, 0x0)
	/tmp/farm/go/src/runtime/mcentral.go:232 +0xac fp=0xc000052b08 sp=0xc000052ac8 pc=0x12001e2a4
runtime.(*mcentral).cacheSpan(0x120a25918, 0x0)
	/tmp/farm/go/src/runtime/mcentral.go:158 +0x424 fp=0xc000052b68 sp=0xc000052b08 pc=0x12001dfcc
runtime.(*mcache).refill(0x7ffff23e45b8, 0xb)
	/tmp/farm/go/src/runtime/mcache.go:162 +0x10c fp=0xc000052bc0 sp=0xc000052b68 pc=0x12001d0e4
runtime.(*mcache).nextFree(0x7ffff23e45b8, 0xb, 0x120010a20, 0x1203979d0, 0x1205d78a0)
	/tmp/farm/go/src/runtime/malloc.go:882 +0xb0 fp=0xc000052bf8 sp=0xc000052bc0 pc=0x1200101d0
runtime.mallocgc(0x25, 0x0, 0xc000073f00, 0xc0005a2780)
	/tmp/farm/go/src/runtime/malloc.go:1069 +0x8c0 fp=0xc000052ca8 sp=0xc000052bf8 pc=0x120010c90
runtime.rawstring(0x25, 0x0, 0x0, 0x0, 0x0, 0x0)
	/tmp/farm/go/src/runtime/string.go:263 +0x58 fp=0xc000052cd0 sp=0xc000052ca8 pc=0x1200653b0
runtime.rawstringtmp(0x0, 0x25, 0xc000073f40, 0xc00003b660, 0xffffffffffffffff, 0xc00003b670, 0xffffffffffffffff)
	/tmp/farm/go/src/runtime/string.go:131 +0x9c fp=0xc000052d08 sp=0xc000052cd0 pc=0x120064cd4
runtime.concatstrings(0x0, 0xc000052e98, 0x6, 0x6, 0xc00068e058, 0x120059ff4)
	/tmp/farm/go/src/runtime/string.go:50 +0xb8 fp=0xc000052d98 sp=0xc000052d08 pc=0x120064700
cmd/go/internal/work.(*Builder).Do.func2(0x120744fe8, 0xc0000a2000, 0xc0005f0140)
	/tmp/farm/go/src/cmd/go/internal/work/exec.go:129 +0x464 fp=0xc000052f08 sp=0xc000052d98 pc=0x1205193e4
cmd/go/internal/work.(*Builder).Do.func3(0xc0002f2030, 0xc0006fbd60, 0xc0004f9a00, 0xc000487f98)
	/tmp/farm/go/src/cmd/go/internal/work/exec.go:198 +0xb4 fp=0xc000052fb8 sp=0xc000052f08 pc=0x1205196f4
runtime.goexit()
	/tmp/farm/go/src/runtime/asm_mips64x.s:631 +0x4 fp=0xc000052fb8 sp=0xc000052fb8 pc=0x120080f5c
created by cmd/go/internal/work.(*Builder).Do
	/tmp/farm/go/src/cmd/go/internal/work/exec.go:184 +0x420

2020-12-04T16:16:41-6607ba8/openbsd-386-64
2020-12-04T05:15:55-214da9f/openbsd-386-64
2020-12-02T20:03:35-bef1c47/openbsd-386-64
2020-11-19T13:27:11-4783bc9/openbsd-386-64
2020-11-16T00:27:33-ac45abd/openbsd-386-64
2020-11-12T18:51:08-eeaa07d/openbsd-386-64
2020-05-13T12:28:04-866d71a/openbsd-386-64
2020-04-27T16:39:59-9ea0146/openbsd-386-64
2020-04-21T04:27:24-cfa8b22/openbsd-386-64
2020-04-16T04:05:44-1839561/openbsd-386-64
2020-04-14T20:27:33-3bb7580/openbsd-386-64
2020-04-14T18:42:46-9129589/openbsd-386-64
2020-04-14T03:22:29-332987a/openbsd-386-64

CC @aclements @mknyszek @prattmic

[mknyszek]

...huh. What's crashing here is systemstack, I think? I don't think it's usually supposed to be passed a nil pointer... the function is known statically.

I suspect memory corruption.

[cherrymui]

I suspect memory corruption.

Probably. It could be some issue on that machine, see the late few comments on #42229.

The OpenBSD failures look different.

[mknyszek]

I agree, the OpenBSD failures look different, and seem to be in mspan.init which is strange. I'll take a look into that in a bit.

[jrick]

OpenBSD failures look like #34988 (note that each the traces include calls to os/exec.Cmd.Start).

[bcmills]

The linux-mips64le-mengzhuo failure looks like #58212.

[bcmills]

Duplicate of #58212