pthread_create crash: gofuzz, cgo, asan, go 1.16

[Nigel Tao]

As per

https://github.com/google/oss-fuzz/issues/5442

Some Go fuzzer programs (configured with whatever oss-fuzz does to combine Go with the address sanitizer) are crashing with:

Crash Type: Null-dereference READ

Crash Address: 0x000000000000
Crash State:
pthread_create
_cgo_try_pthread_create
pthread_create

The actual Go code under test does not spawn its own goroutines, although it does involve asm code which IIUC is similar to cgo:

https://github.com/google/oss-fuzz/blob/master/projects/go-snappy/fuzz.go

https://github.com/golang/snappy/blob/master/decode.go

https://github.com/golang/snappy/blob/master/decode_amd64.s

Another comment in that 5442 issue says:

This bug happens for every golang project since go 1.16
I think it happened as well in go 1.15 but only for fuzz targets running multiple goroutines

So perhaps the asm thing is unrelated??

I know there's not a lot of detail here, but if anyone has suggestions on what to try next, speak here or on https://github.com/google/oss-fuzz/issues/5442

[Nigel Tao]

On Sat, Mar 20, 2021 at 10:29 AM Nigel Tao <nige...@golang.org> wrote:

I know there's not a lot of detail here, but if anyone has suggestions on what to try next, speak here or on https://github.com/google/oss-fuzz/issues/5442

Is anyone else seeing this? Does anyone have suggestions? This Go-fuzzing issue is still regularly generating a number of false positives that are reportedly only since go 1.16.

[Nigel Tao]

I copy/pasted the OP to https://github.com/golang/go/issues/46467 in case this is better tracked as a GitHub issue.