On Fri, Jul 26, 2019 at 5:57 PM Catalin Marinas <catalin.marinas@xxxxxxx> wrote: > > On Fri, Jul 26, 2019 at 05:20:55PM +0200, Dmitry Vyukov wrote: > > On Fri, Jul 26, 2019 at 3:00 PM Catalin Marinas <catalin.marinas@xxxxxxx> wrote: > > > On Wed, Jul 24, 2019 at 12:18:07PM -0700, syzbot wrote: > > > > syzbot found the following crash on: > > > > > > > > HEAD commit: c6dd78fc Merge branch 'x86-urgent-for-linus' of git://git... > > > > git tree: upstream > > > > console output: https://syzkaller.appspot.com/x/log.txt?x=15fffef4600000 > > > > kernel config: https://syzkaller.appspot.com/x/.config?x=8de7d700ea5ac607 > > > > dashboard link: https://syzkaller.appspot.com/bug?extid=a871c1e6ea00685e73d7 > > > > compiler: gcc (GCC) 9.0.0 20181231 (experimental) > > > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=127b0334600000 > > > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12609e94600000 > > > > > > > > The bug was bisected to: > > > > > > > > commit 0e5f7d0b39e1f184dc25e3adb580c79e85332167 > > > > Author: Nicolas Ferre <nicolas.ferre@xxxxxxxxx> > > > > Date: Wed Mar 16 13:19:49 2016 +0000 > > > > > > > > ARM: dts: at91: shdwc binding: add new shutdown controller documentation > > > > > > That's another wrong commit identification (a documentation patch should > > > not cause a memory leak). > > > > > > I don't really think kmemleak, with its relatively high rate of false > > > positives, is suitable for automated testing like syzbot. You could > > > > Do you mean automated testing in general, or bisection only? > > The wrong commit identification is related to bisection only, but you > > generalized it to automated testing in general. So which exactly you > > mean? > > I probably meant both. In terms of automated testing and reporting, if > the false positives rate is high, people start ignoring the reports. So > it requires some human checking first (or make the tool more robust). > > W.r.t. bisection, the false negatives (rather than positives) will cause > the tool to miss the problematic commit and misreport. I'm not sure you > can make the reporting deterministic on successive runs given that you > changed the kernel HEAD (for bisection). But it may get better if you > have a "stopscan" kmemleak option which freezes the machine during > scanning (it has been discussed in the past but I really struggle to > find time to work on it; any help appreciated ;)). Do you have any data points wrt automated testing in general? This disagrees with what I see. For bisection, I agree. Need to look at the data we got over the past days when it become enabled. But I suspect that, yes, false positives, flakes, and other true leaks can make it infeasible.
