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From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Daniel Borkmann <daniel@iogearbox.net>
Cc: Alexei Starovoitov <ast@kernel.org>, bpf <bpf@vger.kernel.org>,
	Network Development <netdev@vger.kernel.org>,
	Yonghong Song <yhs@fb.com>, Martin KaFai Lau <kafai@fb.com>
Subject: Re: [PATCH bpf] bpf: Fix use after free in bpf_get_prog_name
Date: Tue, 22 Oct 2019 22:00:54 -0700	[thread overview]
Message-ID: <CAADnVQKYv1YAv_jwQLHQYKdEcJCioKG0AfWRnGmwO=jqL9+jdw@mail.gmail.com> (raw)
In-Reply-To: <875f2906a7c1a0691f2d567b4d8e4ea2739b1e88.1571779205.git.daniel@iogearbox.net>

On Tue, Oct 22, 2019 at 2:30 PM Daniel Borkmann <daniel@iogearbox.net> wrote:
>
> There is one more problematic case I noticed while recently fixing BPF kallsyms
> handling in cd7455f1013e ("bpf: Fix use after free in subprog's jited symbol
> removal") and that is bpf_get_prog_name().
>
> If BTF has been attached to the prog, then we may be able to fetch the function
> signature type id in kallsyms through prog->aux->func_info[prog->aux->func_idx].type_id.
> However, while the BTF object itself is torn down via RCU callback, the prog's
> aux->func_info is immediately freed via kvfree(prog->aux->func_info) once the
> prog's refcount either hit zero or when subprograms were already exposed via
> kallsyms and we hit the error path added in 5482e9a93c83 ("bpf: Fix memleak in
> aux->func_info and aux->btf").
>
> This violates RCU as well since kallsyms could be walked in parallel where we
> could access aux->func_info. Hence, defer kvfree() to after RCU grace period.
> Looking at ba64e7d85252 ("bpf: btf: support proper non-jit func info") there
> is no reason/dependency where we couldn't defer the kvfree(aux->func_info) into
> the RCU callback.
>
> Fixes: 5482e9a93c83 ("bpf: Fix memleak in aux->func_info and aux->btf")
> Fixes: ba64e7d85252 ("bpf: btf: support proper non-jit func info")
> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
> Cc: Yonghong Song <yhs@fb.com>
> Cc: Martin KaFai Lau <kafai@fb.com>

Applied. Thanks!

      reply	other threads:[~2019-10-23  5:01 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-22 21:30 [PATCH bpf] bpf: Fix use after free in bpf_get_prog_name Daniel Borkmann
2019-10-23  5:00 ` Alexei Starovoitov [this message]

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