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Message-ID: <4a49a98a-d958-8e48-10eb-24bb220e24ed@molgen.mpg.de>
Date:   Mon, 28 Mar 2022 08:51:15 +0200
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Subject: Re: BUG: Bad page state in process systemd-udevd (was: [PATCH v9
 bpf-next 1/9] x86/Kconfig: select HAVE_ARCH_HUGE_VMALLOC with
 HAVE_ARCH_HUGE_VMAP)
Content-Language: en-US
To:     Song Liu <songliubraving@fb.com>,
        Rick P Edgecombe <rick.p.edgecombe@intel.com>
Cc:     Song Liu <song@kernel.org>, Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Andrii Nakryiko <andrii@kernel.org>, Kernel-team@fb.com,
        Peter Zijlstra <peterz@infradead.org>, x86@kernel.org,
        iii@linux.ibm.com, bpf@vger.kernel.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        regressions@lists.linux.dev
References: <20220204185742.271030-1-song@kernel.org>
 <20220204185742.271030-2-song@kernel.org>
 <14444103-d51b-0fb3-ee63-c3f182f0b546@molgen.mpg.de>
 <7edcd673-decf-7b4e-1f6e-f2e0e26f757a@molgen.mpg.de>
 <7F597B8E-72B3-402B-BD46-4C7F13A5D7BD@fb.com>
From:   Paul Menzel <pmenzel@molgen.mpg.de>
In-Reply-To: <7F597B8E-72B3-402B-BD46-4C7F13A5D7BD@fb.com>
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Dear Song,


Am 28.03.22 um 08:37 schrieb Song Liu:
> Thanks Paul for highlighting the issue.

Thank you for getting back to me so quickly.

> + Rick, who highlighted some potential issues with this. (also attached
> the stack trace).

I already had added him, but forgot to document it in the message. Sorry 
for that.

>> On Mar 27, 2022, at 3:36 AM, Paul Menzel <pmenzel@molgen.mpg.de> wrote:

>> Am 26.03.22 um 19:46 schrieb Paul Menzel:
>>> #regzbot introduced: fac54e2bfb5be2b0bbf115fe80d45f59fd773048
>>> #regzbot title: BUG: Bad page state in process systemd-udevd
>>
>>> Am 04.02.22 um 19:57 schrieb Song Liu:
>>>> From: Song Liu <songliubraving@fb.com>
>>>>
>>>> This enables module_alloc() to allocate huge page for 2MB+ requests.
>>>> To check the difference of this change, we need enable config
>>>> CONFIG_PTDUMP_DEBUGFS, and call module_alloc(2MB). Before the change,
>>>> /sys/kernel/debug/page_tables/kernel shows pte for this map. With the
>>>> change, /sys/kernel/debug/page_tables/ show pmd for thie map.
>>>>
>>>> Signed-off-by: Song Liu <songliubraving@fb.com>
>>>> ---
>>>>    arch/x86/Kconfig | 1 +
>>>>    1 file changed, 1 insertion(+)
>>>>
>>>> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
>>>> index 6fddb63271d9..e0e0d00cf103 100644
>>>> --- a/arch/x86/Kconfig
>>>> +++ b/arch/x86/Kconfig
>>>> @@ -159,6 +159,7 @@ config X86
>>>>        select HAVE_ALIGNED_STRUCT_PAGE        if SLUB
>>>>        select HAVE_ARCH_AUDITSYSCALL
>>>>        select HAVE_ARCH_HUGE_VMAP        if X86_64 || X86_PAE
>>>> +    select HAVE_ARCH_HUGE_VMALLOC        if HAVE_ARCH_HUGE_VMAP
>>>>        select HAVE_ARCH_JUMP_LABEL
>>>>        select HAVE_ARCH_JUMP_LABEL_RELATIVE
>>>>        select HAVE_ARCH_KASAN            if X86_64
>>> Testing Linus’ current master branch, Linux logs critical messages like below:
>>>      BUG: Bad page state in process systemd-udevd  pfn:102e03
>>> I bisected to your commit fac54e2bfb5 (x86/Kconfig: select
>>> HAVE_ARCH_HUGE_VMALLOC with HAVE_ARCH_HUGE_VMAP).
>> 
>> Sorry, I forget to mention, that this is a 32-bit (i686) userspace,
>> but a 64-bit Linux kernel, so it might be the same issue as
>> mentioned in commit eed1fcee556f (x86: Disable
>> HAVE_ARCH_HUGE_VMALLOC on 32-bit x86), but didn’t fix the issue for
>> 64-bit Linux kernel and 32-bit userspace.
> 
> I will look more into this tomorrow. To clarify, what is the 32-bit
> user space that triggers this? Is it systemd-udevd? Is the systemd
> also i686?

Yes, everything – also systemd – is i686. You can build a 32-bit VM 
image with grml-debootstrap [1]:

     sudo DEBOOTSTRAP=mmdebstrap ~/src/grml-debootstrap/grml-debootstrap 
--vm --vmfile --vmsize 3G --target /dev/shm/debian-32.img -r sid --arch 
i686 --filesystem ext4

Then run that with QEMU, but pass the 64-bit Linux kernel to QEMU 
directly with the switches `-kernel` and `-append`, or install the amd64 
Linux kernel into the Debian VM image or the package created with `make 
bindeb-pkg` with `dpkg -i …`.


Kind regards,

Paul


[1]: https://github.com/grml/grml-debootstrap/