On Fri, Dec 04, 2015 at 09:04:35PM +0100, Dmitry Vyukov wrote: > Hello, > > While running syzkaller fuzzer I am seeing lots of the following > use-after-free reports. Unfortunately all my numerous attempts to > reproduce them in a controlled environment failed. They pop up during > fuzzing periodically (once in several hours in a single VM), but > whenever I try to stress-replay what happened in the VM before the > report, the use-after-free does not reproduce. Can somebody > knowledgeable in perf subsystem look at the report? Maybe it is > possible to figure out what happened based purely on the report. I can > pretty reliably test any proposed fixes. > All reports look like this one. Then it is usually followed by other > reports and eventually kernel hangs or dies. What happens in the > fuzzer is essentially random syscalls with random arguments, tasks > born and die concurrently and so on. I was able to reproduce it by > restricting syscalls only to perf_event_open, perf ioctls and bpf > syscall.
For the sake of trying to narrow it down: does the error disappear when you stop using bpf syscall in your fuzzing? If yes, then I could have missed some interaction between perf_event_free, kprobe free and bpf_prog_free. There was a race there before. May be there is still something else. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
