linux-kernel - Re: [PATCH v2] arm64: Enable KCSAN

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Date:   Thu, 2 Dec 2021 11:19:52 +0100
From:   Marco Elver <elver@...gle.com>
To:     Kefeng Wang <wangkefeng.wang@...wei.com>
Cc:     Mark Rutland <mark.rutland@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        joey.gouly@....com
Subject: Re: [PATCH v2] arm64: Enable KCSAN

On Thu, 2 Dec 2021 at 11:16, Marco Elver <elver@...gle.com> wrote:
[...]
> > Reported by Kernel Concurrency Sanitizer on:
> > CPU: 7 PID: 2530 Comm: syz-executor.11 Not tainted 5.10.0+ #113
> > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.104/01/2014
> > ==================================================================
> > BUG: KCSAN: data-race in rwsem_spin_on_owner+0xf4/0x180
> >
> > race at unknown origin, with read to 0xffff9767d3becfac of 4 bytes by task 18119 on cpu 0:
> >  rwsem_spin_on_owner+0xf4/0x180
> >  rwsem_optimistic_spin+0x48/0x480
> >  rwsem_down_read_slowpath+0x4a0/0x670
> >  down_read+0x69/0x190
> >  process_vm_rw+0x41e/0x840
> >  __x64_sys_process_vm_writev+0x76/0x90
> >  do_syscall_64+0x37/0x50
> >  entry_SYSCALL_64_after_hwframe+0x44/0xa9
[...]
> I actually have a "fix" for the data race in rwsem_spin_on_owner, that
> also shows where the other racing access comes from... which reminds me:
> https://lkml.kernel.org/r/20211202101238.33546-1-elver@google.com

Reading be hard ... that patch is for mutex_spin_on_owner. But the
other racing access is the same.

Thanks,
-- Marco