On Fri, Jul 26, 2019 at 6:15 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). > [...] > > Do you have any data points wrt automated testing in general? This > > disagrees with what I see. > > I'm fine with automated testing in general. Just that automated > reporting for kmemleak could be improved a bit to reduce the false > positives (e.g. run it a few times to confirm that it is a real leak). I did a bunch of various external measures in syzkaller to improve kmemleak quality. As far as I see the current rate is close to 100% true positives. We already have 40 leaks (>50%) fixed. Though, kmemleak can be improved too (stop-the-world, etc what we discussed). That would make kmemleak directly usable e.g. during unit-testing, something that's badly needed for kernel. > Just to be clear, I'm not talking about syzbot in general, it's a great > tool, only about improving kmemleak reporting and bisecting.
