Re: [syzbot] BUG: soft lockup in do_wp_page (4)
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From: Will Deacon <will@kernel.org>
Date: 2021-03-25 19:11:07
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On Thu, Mar 25, 2021 at 07:34:54PM +0100, Dmitry Vyukov wrote:
On Thu, Mar 25, 2021 at 7:20 PM Will Deacon [off-list ref] wrote:quoted
On Thu, Mar 18, 2021 at 08:34:16PM +0100, Dmitry Vyukov wrote:quoted
On Thu, Mar 18, 2021 at 8:31 PM syzbot [off-list ref] wrote:quoted
Hello, syzbot found the following issue on: HEAD commit: bf152b0b Merge tag 'for_linus' of git://git.kernel.org/pub.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=17d5264ed00000 kernel config: https://syzkaller.appspot.com/x/.config?x=2c9917c41f0bc04b dashboard link: https://syzkaller.appspot.com/bug?extid=0b036374a865ba0efa8e userspace arch: arm64 Unfortunately, I don't have any reproducer for this issue yet. IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+0b036374a865ba0efa8e@syzkaller.appspotmail.com watchdog: BUG: soft lockup - CPU#0 stuck for 23s! [syz-executor.1:3684]+Will, arm If I am reading this commit correctly, this is caused by: commit cae118b6acc309539b33339e846cbb19187c164c Author: Will Deacon Date: Wed Mar 3 13:49:27 2021 +0000 arm64: Drop support for CMDLINE_EXTEND syzbot passes lots of critical things in CONFIG_CMDLINE: https://github.com/google/syzkaller/blob/c3c81c94865791469d376eba84f4a2d7763d3f71/dashboard/config/linux/upstream-arm64-kasan.config#L495 but also wants the bootloader args to be appended. What is the way to do it now?For now, there isn't a way to do it with CONFIG_CMDLINE, so I think you can either: * Revert my patch for your kernels * Pass the arguments via QEMU's -append option * Take a look at one of the series which should hopefully add this functionality back (but with well-defined semantics) [1] [2]Unfortunately none of these work for syzbot (and I assume other testing environments). syzbot does not support custom patches by design: http://bit.do/syzbot#no-custom-patches As any testing system, it tests the official trees. It's not humans who start these VMs, so it's not as easy as changing the command line after typing... There is no support for passing args specifically to qemu, syzkaller support not just qemu, so these things are specifically localized in the config. Additionally there is an issue of communicating all these scattered details to developers in bug reports. Currently syzbot reports the kernel config and it as well captures command line. Could you revert the patch? Is there any point in removing the currently supported feature before the new feature lands?
Well, we only just merged it (in 5.10 I think?), and the semantics of the new version will be different, so I really don't see the value in supporting both (even worse, Android has its own implementation which is different again). The timeline was: we merged CMDLINE_EXTEND, then we noticed it was broken, my fixes were rejected, so we removed the feature rather than support the broken version. In the relatively small window while it was merged, syzbot started using it :( So I really think the best bet is to wait until the patches are sorted out. I think Christophe is about to spin a new version, and I reviewed his last copy, so I don't see this being far off, Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel