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From:   Dmitry Vyukov <dvyukov@google.com>
Date:   Sat, 19 Jan 2019 17:45:18 +0100
Message-ID: <CACT4Y+ZxgzdbCeFquYmKThfiTGg3pZhn90X_Fk3yRXGYfepU4Q@mail.gmail.com>
Subject: Re: [RESEND BUG REPORT] System hung! Due to ftrace or KASAN?
To:     Zenghui Yu <zenghuiyu96@gmail.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Andy Lutomirski <luto@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>,
        "the arch/x86 maintainers" <x86@kernel.org>
Cc:     Steven Rostedt <rostedt@goodmis.org>,
        linux-trace-devel@vger.kernel.org,
        kasan-dev <kasan-dev@googlegroups.com>,
        "open list:KERNEL BUILD + fi..." <linux-kbuild@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
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Sender: linux-kernel-owner@vger.kernel.org
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On Sat, Jan 19, 2019 at 5:37 PM Dmitry Vyukov <dvyukov@google.com> wrote:
>
> On Fri, Jan 18, 2019 at 6:45 PM Zenghui Yu <zenghuiyu96@gmail.com> wrote:
> >
> > Hi, All!
> >
> > I compiled the latest kernel and installed it on my old laptop (Hardware name:
> > Hewlett-Packard HP ProBook 440 G2/2247, BIOS M74 Ver. 01.02 06/17/2014).  But
> > when I tried to enable function tracer via debugfs, the system went _hung_!
> > Compared with the last kernel compiling process, the only change I have made
> > is that I enabled KASAN configuration this time.
> >
> > Reproducing this issue is simple as below:
> >
> >         0. `uname -a` shows:
> >                 Linux ubuntuu 5.0.0-rc2+ #9 SMP Fri Jan 18 03:04:01 CST 2019
> >                 x86_64 x86_64 x86_64 GNU/Linux
> >
> >         1. `make menuconfig` to enable KASAN configuration:
> >                 Kernel hacking ---> Memory Debugging --->
> >                 KASAN: runtime memory debugger
> >
> >            compile, install, reboot, then `dmesg | grep kasan` shows:
> >                 [    0.342882] kasan: KernelAddressSanitizer initialized
> >
> >         2. enable function tracer
> >                 `echo function > /sys/kernel/debug/tracing/current_tracer`
> >            (then my poor laptop was locked and didn't respond to me ...)
> >
> > What's more, enabling function graph tracer will suffer from the same problem.
> > I have no idea about what wrong thing had happened inside kernel --
> > about ftrace,
> > or about KASAN?  So I report it to you and waiting for your solution!
> >
> > I have provided my *.config* file as attachment for those who're interested in
> > this issue.  But sorry for that I can't provide any useful call trace
> > because the
> > system went down so quickly.
> >
> > P.S. I'm a newcomer for KASAN. If any mis-configuration or
> > mis-understand, please
> > fix me up and let me know :).
>
> Hi Zenghui,
>
> I've tried to reproduce this, but kernel crashes during boot with this
> config for me.
> I am commit 2339e91d0e6609e17943a0ab3c3c8c4044760c05, the config is
> basically yours but updated for newer compiler and with builtin
> modules:
> https://gist.githubusercontent.com/dvyukov/9af234617749aa4eada67ba8c2e4f46c/raw/d0e09ddf255962313a82bb552c3fc0d832fa6844/gistfile1.txt

I've commented out the warning locally for now and can reproduce the
hang. You need this commit, it fixes the hang:
https://groups.google.com/forum/#!topic/kasan-dev/g8A8PLKCyoE

> TITLE: WARNING in note_page
> MAINTAINERS: [dave.hansen@linux.intel.com luto@kernel.org
> peterz@infradead.org tglx@linutronix.de mingo@redhat.com bp@alien8.de
> hpa@zytor.com x86@kernel.org linux-kernel@vger.kernel.org]
>
> ------------[ cut here ]------------
> x86/mm: Found insecure W+X mapping at address native_usergs_sysret64+0x0/0x10
> WARNING: CPU: 3 PID: 1 at arch/x86/mm/dump_pagetables.c:263 note_wx
> arch/x86/mm/dump_pagetables.c:262 [inline]
> WARNING: CPU: 3 PID: 1 at arch/x86/mm/dump_pagetables.c:263
> note_page+0x800/0xaf0 arch/x86/mm/dump_pagetables.c:302
> Kernel panic - not syncing: panic_on_warn set ...
> CPU: 3 PID: 1 Comm: swapper/0 Not tainted 5.0.0-rc2+ #16
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
> Call Trace:
>  __dump_stack lib/dump_stack.c:77 [inline]
>  dump_stack+0x7b/0xb5 lib/dump_stack.c:113
>  panic+0x18e/0x351 kernel/panic.c:214
>  __warn+0x13c/0x140 kernel/panic.c:571
>  report_bug+0xd7/0x140 lib/bug.c:186
>  fixup_bug.part.11+0x2d/0x60 arch/x86/kernel/traps.c:178
>  fixup_bug arch/x86/include/asm/paravirt.h:776 [inline]
>  do_error_trap+0xb6/0xc0 arch/x86/kernel/traps.c:271
>  do_invalid_op+0x3b/0x50 arch/x86/kernel/traps.c:290
>  invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:973
> RIP: 0010:note_wx arch/x86/mm/dump_pagetables.c:262 [inline]
> RIP: 0010:note_page+0x800/0xaf0 arch/x86/mm/dump_pagetables.c:302
> Code: 4d 32 00 4c 89 7b 28 48 c7 43 30 00 00 00 00 e9 46 fc ff ff 4c
> 89 ee 48 c7 c7 a0 35 c5 ae c6 05 02 81 1e 02 01 e8 50 93 01 00 <0f> 0b
> 48 8b 7d 90 e8 75 4c 32 00 48 8b 43 20 48 89 45 c8 e9 72 f9
> RSP: 0000:ffff88805d5c7d18 EFLAGS: 00010286
> RAX: 0000000000000000 RBX: ffff88805d5c7e58 RCX: ffffffffae7f11db
> RDX: 0000000000000001 RSI: 0000000000000004 RDI: 0000000000000246
> RBP: ffff88805d5c7da0 R08: ffffed100bab8f5c R09: ffffed100bab8f5c
> R10: 0000000000000002 R11: ffffed100bab8f5c R12: 0000000000000000
> R13: ffffffffae800000 R14: 0000000000000004 R15: 0000000000000000
>  walk_pmd_level arch/x86/mm/dump_pagetables.c:428 [inline]
>  walk_pud_level arch/x86/mm/dump_pagetables.c:459 [inline]
>  walk_p4d_level arch/x86/mm/dump_pagetables.c:484 [inline]
>  ptdump_walk_pgd_level_core+0x566/0x6e0 arch/x86/mm/dump_pagetables.c:552
>  ptdump_walk_user_pgd_level_checkwx+0x4e/0x50 arch/x86/mm/dump_pagetables.c:600
>  pti_finalize+0x27/0xaf arch/x86/mm/pti.c:682
>  kernel_init+0x3e/0x130 init/main.c:1066
>  ret_from_fork+0x35/0x40 arch/x86/entry/entry_64.S:352
> Kernel Offset: 0x2c800000 from 0xffffffff81000000 (relocation range:
> 0xffffffff80000000-0xffffffffbfffffff)
> Rebooting in 86400 seconds..