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

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Date:   Fri, 5 Jul 2019 10:24:52 -0700
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Jiri Olsa <jolsa@...nel.org>, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Michael Petlan <mpetlan@...hat.com>, netdev@...r.kernel.org,
        bpf@...r.kernel.org, Martin KaFai Lau <kafai@...com>,
        Quentin Monnet <quentin.monnet@...ronome.com>
Subject: Re: [PATCHv2] tools bpftool: Fix json dump crash on powerpc

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 :)):

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>