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

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Message-ID: <20190709175333.GE9579@krava>
Date:   Tue, 9 Jul 2019 19:53:33 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Daniel Borkmann <daniel@...earbox.net>
Cc:     Quentin Monnet <quentin.monnet@...ronome.com>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        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 Sat, Jul 06, 2019 at 12:00:44AM +0200, Daniel Borkmann wrote:
> 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.

will do, thanks
jirka