linux-kernel - Re: BUG: unable to handle kernel paging request in bpf_probe_read_compat

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Date: Thu, 21 Dec 2023 09:15:31 +0800
From: Hou Tao <houtao@...weicloud.com>
To: Yonghong Song <yonghong.song@...ux.dev>,
 xingwei lee <xrivendell7@...il.com>
Cc: ast@...nel.org, jolsa@...nel.org, daniel@...earbox.net,
 john.fastabend@...il.com, kpsingh@...nel.org, sdf@...gle.com,
 haoluo@...gle.com, rostedt@...dmis.org, mhiramat@...nel.org,
 mathieu.desnoyers@...icios.com, bpf@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
 song@...nel.org
Subject: Re: BUG: unable to handle kernel paging request in
 bpf_probe_read_compat_str

Hi,

On 12/21/2023 1:50 AM, Yonghong Song wrote:
>
> On 12/20/23 1:19 AM, Hou Tao wrote:
>> Hi,
>>
>> On 12/14/2023 11:40 AM, xingwei lee wrote:
>>> Hello I found a bug in net/bpf in the lastest upstream linux and
>>> comfired in the lastest net tree and lastest net bpf titled BUG:
>>> unable to handle kernel paging request in bpf_probe_read_compat_str
>>>
>>> If you fix this issue, please add the following tag to the commit:
>>> Reported-by: xingwei Lee <xrivendell7@...il.com>
>>>
>>> kernel: net 9702817384aa4a3700643d0b26e71deac0172cfd / bpf
>>> 2f2fee2bf74a7e31d06fc6cb7ba2bd4dd7753c99
>>> Kernel config:
>>> https://syzkaller.appspot.com/text?tag=KernelConfig&x=b50bd31249191be8
>>>
>>> in the lastest bpf tree, the crash like:
>>>
>>> TITLE: BUG: unable to handle kernel paging request in
>>> bpf_probe_read_compat_str
>>> CORRUPTED: false ()
>>> MAINTAINERS (TO): [akpm@...ux-foundation.org linux-mm@...ck.org]
>>> MAINTAINERS (CC): [linux-kernel@...r.kernel.org]
>>>
>>> BUG: unable to handle page fault for address: ff0
>> Thanks for the report and reproducer. The output is incomplete. It
>> should be: "BUG: unable to handle page fault for address:
>> ffffffffff600000". The address is a vsyscall address, so
>> handle_page_fault() considers that the fault address is in userspace
>> instead of kernel space, and there will be no fix-up for the exception
>> and oops happened. Will post a fix and a selftest for it.
>
> There is a proposed fix here:
>
> https://lore.kernel.org/bpf/87r0jwquhv.ffs@tglx/
>
> Not sure the fix in the above link is merged to some upstream branch
> or not.

It seems it has not been merged. will ping Thomas later.