netdev - Re: [PATCHv2] tools bpftool: Fix json dump crash on powerpc

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Message-ID: <5168f635-a23c-eac3-479d-747e55adfc4c@iogearbox.net>
Date:   Sat, 6 Jul 2019 00:00:44 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Quentin Monnet <quentin.monnet@...ronome.com>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Jiri Olsa <jolsa@...hat.com>
Cc:     Jiri Olsa <jolsa@...nel.org>, Alexei Starovoitov <ast@...nel.org>,
        Michael Petlan <mpetlan@...hat.com>, netdev@...r.kernel.org,
        bpf@...r.kernel.org, Martin KaFai Lau <kafai@...com>
Subject: Re: [PATCHv2] tools bpftool: Fix json dump crash on powerpc

On 07/05/2019 07:26 PM, Quentin Monnet wrote:
> 2019-07-05 10:24 UTC-0700 ~ Jakub Kicinski <jakub.kicinski@...ronome.com>
>> On Fri, 5 Jul 2019 14:10:31 +0200, Jiri Olsa wrote:
>>> Michael reported crash with by bpf program in json mode on powerpc:
>>>
>>>   # bpftool prog -p dump jited id 14
>>>   [{
>>>         "name": "0xd00000000a9aa760",
>>>         "insns": [{
>>>                 "pc": "0x0",
>>>                 "operation": "nop",
>>>                 "operands": [null
>>>                 ]
>>>             },{
>>>                 "pc": "0x4",
>>>                 "operation": "nop",
>>>                 "operands": [null
>>>                 ]
>>>             },{
>>>                 "pc": "0x8",
>>>                 "operation": "mflr",
>>>   Segmentation fault (core dumped)
>>>
>>> The code is assuming char pointers in format, which is not always
>>> true at least for powerpc. Fixing this by dumping the whole string
>>> into buffer based on its format.
>>>
>>> Please note that libopcodes code does not check return values from
>>> fprintf callback, but as per Jakub suggestion returning -1 on allocation
>>> failure so we do the best effort to propagate the error. 
>>>
>>> Reported-by: Michael Petlan <mpetlan@...hat.com>
>>> Signed-off-by: Jiri Olsa <jolsa@...nel.org>
>>
>> Thanks, let me repost all the tags (Quentin, please shout if you're
>> not ok with this :)):
> 
> I confirm it's all good for me, thanks :)
> 
>> Fixes: 107f041212c1 ("tools: bpftool: add JSON output for `bpftool prog dump jited *` command")
>> Reviewed-by: Quentin Monnet <quentin.monnet@...ronome.com>
>> Reviewed-by: Jakub Kicinski <jakub.kicinski@...ronome.com>

Given merge window coming up, I've applied this to bpf-next, thanks everyone!

P.s.: Jiri, please repost full/proper patch next time instead of inline reply.