linux-kernel - Re: [PATCH bpf v2] bpftool: Don't crash on missing jited insns or ksyms

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Message-ID: <20191210213148.kqd6xdvqjkh3zxst@ast-mbp.dhcp.thefacebook.com>
Date:   Tue, 10 Dec 2019 13:31:50 -0800
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Jakub Kicinski <jakub.kicinski@...ronome.com>
Cc:     Toke Høiland-Jørgensen <toke@...hat.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        lkml <linux-kernel@...r.kernel.org>, netdev@...r.kernel.org,
        bpf@...r.kernel.org, Martin Lau <kafai@...com>
Subject: Re: [PATCH bpf v2] bpftool: Don't crash on missing jited insns or
 ksyms

On Tue, Dec 10, 2019 at 01:24:28PM -0800, Jakub Kicinski wrote:
> On Tue, 10 Dec 2019 22:09:55 +0100, Toke Høiland-Jørgensen wrote:
> > Jakub Kicinski <jakub.kicinski@...ronome.com> writes:
> > > On Tue, 10 Dec 2019 19:14:12 +0100, Toke Høiland-Jørgensen wrote:  
> > >> When the kptr_restrict sysctl is set, the kernel can fail to return
> > >> jited_ksyms or jited_prog_insns, but still have positive values in
> > >> nr_jited_ksyms and jited_prog_len. This causes bpftool to crash when trying
> > >> to dump the program because it only checks the len fields not the actual
> > >> pointers to the instructions and ksyms.
> > >> 
> > >> Fix this by adding the missing checks.
> > >> 
> > >> Signed-off-by: Toke Høiland-Jørgensen <toke@...hat.com>  
> > >
> > > Fixes: 71bb428fe2c1 ("tools: bpf: add bpftool")
> > >
> > > and
> > >
> > > Fixes: f84192ee00b7 ("tools: bpftool: resolve calls without using imm field")
> > >
> > > ?  
> > 
> > Yeah, guess so? Although I must admit it's not quite clear to me whether
> > bpftool gets stable backports, or if it follows the "only moving
> > forward" credo of libbpf?
> 
> bpftool does not have a GH repo, and seeing strength of Alexei's
> arguments in the recent discussion - I don't think it will. So no
> reason for bpftool to be "special"

bpftool always was and will be a special user of libbpf.