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runtime: moduledata.typemap use after garbage collection #17680

crawshaw opened this issue Oct 31, 2016 · 1 comment


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commented Oct 31, 2016

The runtime.moduledata map[typeOff]*_type object is created at run time and stored in the moduledata. The moduledata object is marked by the linker as SNOPTRDATA, so the reference is ignored by the GC. Running misc/cgo/testplugin/test.bash with GOGC=1 will eventually collect the typemap and crash.

bash:~/go/misc/cgo/testplugin$ GOGC=1 ./test.bash
unexpected fault address 0xb01dfacedebac1e
fatal error: fault
[signal SIGSEGV: segmentation violation code=0x1 addr=0xb01dfacedebac1e pc=0x400c4cd]

goroutine 1 [running]:
runtime.throw(0x40e193b, 0x5)
    /Users/crawshaw/go/src/runtime/panic.go:596 +0x95 fp=0xc42003f648 sp=0xc42003f628
    /Users/crawshaw/go/src/runtime/signal_unix.go:276 +0x28c fp=0xc42003f698 sp=0xc42003f648
runtime.mapaccess1_fast32(0x40c9240, 0xc4200a8120, 0x54c0, 0xc4200fa0e0)
    /Users/crawshaw/go/src/runtime/hashmap_fast.go:37 +0x16d fp=0xc42003f6c0 sp=0xc42003f698
    /Users/crawshaw/go/src/runtime/type.go:484 +0x59c fp=0xc42003f8b0 sp=0xc42003f6c0
plugin.lastmoduleinit(0x4802000, 0xc4200aa018, 0x5500000)
    /Users/crawshaw/go/src/runtime/plugin.go:48 +0x7c5 fp=0xc42003f990 sp=0xc42003f8b0, 0x35, 0x0, 0x0, 0x0)
    /Users/crawshaw/go/src/plugin/plugin_dlopen.go:72 +0x241 fp=0xc42003fbb0 sp=0xc42003f990
plugin.Open(0xc420010200, 0x35, 0xc420010200, 0x35, 0x0)
    /Users/crawshaw/go/src/plugin/plugin.go:30 +0x35 fp=0xc42003fbe8 sp=0xc42003fbb0
    /Users/crawshaw/go/misc/cgo/testplugin/src/host/host.go:59 +0x42c fp=0xc42003ff88 sp=0xc42003fbe8
    /Users/crawshaw/go/src/runtime/proc.go:185 +0x20a fp=0xc42003ffe0 sp=0xc42003ff88
    /Users/crawshaw/go/src/runtime/asm_amd64.s:2184 +0x1 fp=0xc42003ffe8 sp=0xc42003ffe0

goroutine 17 [syscall, locked to thread]:
    /Users/crawshaw/go/src/runtime/asm_amd64.s:2184 +0x1

cc @mwhudson

@crawshaw crawshaw added this to the Go1.8 milestone Oct 31, 2016

@crawshaw crawshaw self-assigned this Oct 31, 2016


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commented Oct 31, 2016

CL mentions this issue.

@gopherbot gopherbot closed this in f4c7a12 Oct 31, 2016

@golang golang locked and limited conversation to collaborators Oct 31, 2017

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