From: Kumar Kartikeya Dwivedi <memxor@gmail.com>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Yonghong Song <yhs@fb.com>, bpf <bpf@vger.kernel.org>,
Alexei Starovoitov <ast@kernel.org>,
Andrii Nakryiko <andrii@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
John Fastabend <john.fastabend@gmail.com>,
Kernel Team <kernel-team@fb.com>,
Martin KaFai Lau <martin.lau@kernel.org>
Subject: Re: [PATCH bpf-next v4 3/4] bpf: Add a kfunc for generic type cast
Date: Mon, 21 Nov 2022 02:19:30 +0530 [thread overview]
Message-ID: <20221120204930.uuinebxndf7vkdwy@apollo> (raw)
In-Reply-To: <CAADnVQ+92vwqUB=J-QJYtrW0Yqvx2HAJJBREkXPJtW0+gyS1mQ@mail.gmail.com>
On Mon, Nov 21, 2022 at 01:46:04AM IST, Alexei Starovoitov wrote:
> On Sun, Nov 20, 2022 at 11:57 AM Yonghong Song <yhs@fb.com> wrote:
> >
> > @@ -8938,6 +8941,24 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
> > regs[BPF_REG_0].type = PTR_TO_BTF_ID | PTR_TRUSTED;
> > regs[BPF_REG_0].btf = desc_btf;
> > regs[BPF_REG_0].btf_id = meta.ret_btf_id;
> > + } else if (meta.func_id == special_kfunc_list[KF_bpf_rdonly_cast]) {
> > + if (!capable(CAP_PERFMON)) {
> > + verbose(env,
> > + "kfunc bpf_rdonly_cast requires CAP_PERFMON capability\n");
> > + return -EACCES;
> > + }
>
> Just realized that bpf_cast_to_kern_ctx() has to be
> gated by cap_perfmon as well.
>
> Also the direct capable(CAP_PERFMON) is not quite correct.
> It should at least be perfmon_capable().
> But even better to use env->allow_ptr_leaks here.
Based on this, I wonder if this needs to be done for bpf_obj_new as well? It
doesn't zero initialize the memory it returns (except special fields, which is
required for correctness), so technically it allows leaking kernel addresses
with just CAP_BPF (apart from capabilities needed for the specific program types
it is available to).
Should that also have a env->allow_ptr_leaks check?
next prev parent reply other threads:[~2022-11-20 20:49 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-20 19:54 [PATCH bpf-next v4 0/4] bpf: Implement two type cast kfuncs Yonghong Song
2022-11-20 19:54 ` [PATCH bpf-next v4 1/4] bpf: Add support for kfunc set with common btf_ids Yonghong Song
2022-11-20 19:54 ` [PATCH bpf-next v4 2/4] bpf: Add a kfunc to type cast from bpf uapi ctx to kernel ctx Yonghong Song
2022-11-20 19:54 ` [PATCH bpf-next v4 3/4] bpf: Add a kfunc for generic type cast Yonghong Song
2022-11-20 20:16 ` Alexei Starovoitov
2022-11-20 20:49 ` Kumar Kartikeya Dwivedi [this message]
2022-11-20 22:34 ` Alexei Starovoitov
2022-11-20 23:32 ` Alexei Starovoitov
2022-11-20 23:47 ` Alexei Starovoitov
2022-11-20 19:54 ` [PATCH bpf-next v4 4/4] bpf: Add type cast unit tests Yonghong Song
2022-11-21 0:00 ` [PATCH bpf-next v4 0/4] bpf: Implement two type cast kfuncs patchwork-bot+netdevbpf
2022-11-21 2:10 ` John Fastabend
2022-11-21 17:29 ` Yonghong Song
2022-11-22 1:48 ` John Fastabend
2022-11-22 4:52 ` Alexei Starovoitov
2022-11-23 3:18 ` John Fastabend
2022-11-23 20:46 ` Alexei Starovoitov
2022-11-29 16:30 ` Alan Maguire
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