linux-kernel - Re: [PATCH] powerpc/kprobes: Fix null pointer reference in arch_prepare

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Message-Id: <1665565982.bae3snm0nx.naveen@linux.ibm.com>
Date:   Wed, 12 Oct 2022 15:22:51 +0530
From:   "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
To:     jniethe5@...il.com, Li Huafei <lihuafei1@...wei.com>,
        mpe@...erman.id.au
Cc:     christophe.leroy@...roup.eu, linux-kernel@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, mhiramat@...nel.org,
        npiggin@...il.com, peterz@...radead.org, rostedt@...dmis.org
Subject: Re: [PATCH] powerpc/kprobes: Fix null pointer reference in
 arch_prepare_kprobe()

Li Huafei wrote:
>>>
>>>   # echo 'p cmdline_proc_show' > kprobe_events
>>>   # echo 'p cmdline_proc_show+16' >> kprobe_events
>> 
>> I think we should extend multiple_kprobes selftest to also place
>> contiguous probes to catch such errors.
>> 
> Yes. But each architecture implementation is different and it looks a
> little difficult to decide which offsets need to be tested.

I don't think we need to be accurate here. A test to simply try putting 
a probe at every byte within the first 256 bytes of a kernel function 
should help catch many such issues. Some of those probes will be 
rejected, but we can ignore errors.


- Naveen