From: Daniel Borkmann <daniel@iogearbox.net>
To: Maciej Fijalkowski <maciej.fijalkowski@intel.com>, ast@kernel.org
Cc: bpf@vger.kernel.org, netdev@vger.kernel.org,
bjorn.topel@intel.com, magnus.karlsson@intel.com
Subject: Re: [PATCH v2 bpf-next 2/6] bpf: propagate poke descriptors to subprograms
Date: Wed, 22 Jul 2020 16:40:42 +0200 [thread overview]
Message-ID: <29a3dcfc-9d85-c113-19d2-e33f80ce5430@iogearbox.net> (raw)
In-Reply-To: <20200721115321.3099-3-maciej.fijalkowski@intel.com>
On 7/21/20 1:53 PM, Maciej Fijalkowski wrote:
> Previously, there was no need for poke descriptors being present in
> subprogram's bpf_prog_aux struct since tailcalls were simply not allowed
> in them. Each subprog is JITed independently so in order to enable
> JITing such subprograms, simply copy poke descriptors from main program
> to subprogram's poke tab.
>
> Add also subprog's aux struct to the BPF map poke_progs list by calling
> on it map_poke_track().
>
> Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
> ---
> kernel/bpf/verifier.c | 20 ++++++++++++++++++++
> 1 file changed, 20 insertions(+)
>
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index 3c1efc9d08fd..3428edf85220 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -9936,6 +9936,9 @@ static int jit_subprogs(struct bpf_verifier_env *env)
> goto out_undo_insn;
>
> for (i = 0; i < env->subprog_cnt; i++) {
> + struct bpf_map *map_ptr;
> + int j;
> +
> subprog_start = subprog_end;
> subprog_end = env->subprog_info[i + 1].start;
>
> @@ -9960,6 +9963,23 @@ static int jit_subprogs(struct bpf_verifier_env *env)
> func[i]->aux->btf = prog->aux->btf;
> func[i]->aux->func_info = prog->aux->func_info;
>
> + for (j = 0; j < prog->aux->size_poke_tab; j++) {
> + int ret;
> +
> + ret = bpf_jit_add_poke_descriptor(func[i],
> + &prog->aux->poke_tab[j]);
> + if (ret < 0) {
> + verbose(env, "adding tail call poke descriptor failed\n");
> + goto out_free;
> + }
> + map_ptr = func[i]->aux->poke_tab[j].tail_call.map;
> + ret = map_ptr->ops->map_poke_track(map_ptr, func[i]->aux);
> + if (ret < 0) {
> + verbose(env, "tracking tail call prog failed\n");
> + goto out_free;
> + }
Hmm, I don't think this is correct/complete. If some of these have been registered or
if later on the JIT'ing fails but the subprog is already exposed to the prog array then
it's /public/ at this point, so a later bpf_jit_free() in out_free will rip them mem
while doing live patching on prog updates leading to UAF.
> + }
> +
> /* Use bpf_prog_F_tag to indicate functions in stack traces.
> * Long term would need debug info to populate names
> */
>
next prev parent reply other threads:[~2020-07-22 14:40 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-21 11:53 [PATCH v2 bpf-next 0/6] bpf: tailcalls in BPF subprograms Maciej Fijalkowski
2020-07-21 11:53 ` [PATCH v2 bpf-next 1/6] bpf, x64: use %rcx instead of %rax for tail call retpolines Maciej Fijalkowski
2020-07-21 11:53 ` [PATCH v2 bpf-next 2/6] bpf: propagate poke descriptors to subprograms Maciej Fijalkowski
2020-07-22 14:40 ` Daniel Borkmann [this message]
2020-07-22 18:37 ` Maciej Fijalkowski
2020-07-22 20:14 ` Daniel Borkmann
2020-07-21 11:53 ` [PATCH v2 bpf-next 3/6] bpf: rename poke descriptor's 'ip' member to 'tailcall_target' Maciej Fijalkowski
2020-07-21 11:53 ` [PATCH v2 bpf-next 4/6] bpf, x64: rework pro/epilogue and tailcall handling in JIT Maciej Fijalkowski
2020-07-21 11:53 ` [PATCH v2 bpf-next 5/6] bpf: allow for tailcalls in BPF subprograms for x64 JIT Maciej Fijalkowski
2020-07-21 11:53 ` [PATCH v2 bpf-next 6/6] selftests: bpf: add dummy prog for bpf2bpf with tailcall Maciej Fijalkowski
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