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From: Andrii Nakryiko <andrii.nakryiko@gmail.com>
To: "Toke Høiland-Jørgensen" <toke@redhat.com>
Cc: Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
	Yonghong Song <yhs@fb.com>, Andrii Nakryiko <andriin@fb.com>,
	John Fastabend <john.fastabend@gmail.com>,
	Jiri Olsa <jolsa@redhat.com>,
	Eelco Chaudron <echaudro@redhat.com>,
	KP Singh <kpsingh@chromium.org>,
	Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>
Subject: Re: [PATCH bpf-next v7 03/10] bpf: verifier: refactor check_attach_btf_id()
Date: Mon, 21 Sep 2020 16:05:53 -0700	[thread overview]
Message-ID: <CAEf4BzY4UR+KjZ3bY6ykyW5CPNwAzwgKVhYHGdgDuMT2nntmTg@mail.gmail.com> (raw)
In-Reply-To: <160051618622.58048.13304507277053169557.stgit@toke.dk>

On Sat, Sep 19, 2020 at 4:50 AM Toke Høiland-Jørgensen <toke@redhat.com> wrote:
>
> From: Toke Høiland-Jørgensen <toke@redhat.com>
>
> The check_attach_btf_id() function really does three things:
>
> 1. It performs a bunch of checks on the program to ensure that the
>    attachment is valid.
>
> 2. It stores a bunch of state about the attachment being requested in
>    the verifier environment and struct bpf_prog objects.
>
> 3. It allocates a trampoline for the attachment.
>
> This patch splits out (1.) and (3.) into separate functions in preparation
> for reusing them when the actual attachment is happening (in the
> raw_tracepoint_open syscall operation), which will allow tracing programs
> to have multiple (compatible) attachments.
>
> No functional change is intended with this patch.
>
> Acked-by: Andrii Nakryiko <andriin@fb.com>
> Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
> ---

Ok, so bad news: you broke another selftest (test_overhead). Please,
do run test_progs and make sure everything succeeds, every time before
you post a new version.

Good news, though, is that this refactoring actually fixed a pretty
nasty bug in check_attach_btf_id logic: whenever bpf_trampoline
already existed (e.g., due to successful fentry to function X), all
subsequent fentry/fexit/fmod_ret and all their sleepable variants
would skip a bunch of check. So please attach the following Fixes
tags:

Fixes: 6ba43b761c41 ("bpf: Attachment verification for BPF_MODIFY_RETURN")
Fixes: 1e6c62a88215 ("bpf: Introduce sleepable BPF programs")

As for selftests, feel free to just drop the fmod_ret program, it was
never supposed to be possible, I just never realized that.

>  include/linux/bpf.h          |    7 +
>  include/linux/bpf_verifier.h |    9 ++
>  kernel/bpf/trampoline.c      |   20 ++++
>  kernel/bpf/verifier.c        |  197 ++++++++++++++++++++++++------------------
>  4 files changed, 149 insertions(+), 84 deletions(-)
>

[...]

  reply	other threads:[~2020-09-21 23:06 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-19 11:49 [PATCH bpf-next v7 00/10] bpf: Support multi-attach for freplace programs Toke Høiland-Jørgensen
2020-09-19 11:49 ` [PATCH bpf-next v7 01/10] bpf: disallow attaching modify_return tracing functions to other BPF programs Toke Høiland-Jørgensen
2020-09-21 22:39   ` Andrii Nakryiko
2020-09-22  9:52     ` Toke Høiland-Jørgensen
2020-09-19 11:49 ` [PATCH bpf-next v7 02/10] bpf: change logging calls from verbose() to bpf_log() and use log pointer Toke Høiland-Jørgensen
2020-09-19 11:49 ` [PATCH bpf-next v7 03/10] bpf: verifier: refactor check_attach_btf_id() Toke Høiland-Jørgensen
2020-09-21 23:05   ` Andrii Nakryiko [this message]
2020-09-22 10:14     ` Toke Høiland-Jørgensen
2020-09-22 11:16     ` Toke Høiland-Jørgensen
2020-09-22 16:28       ` Andrii Nakryiko
2020-09-22 17:41         ` Toke Høiland-Jørgensen
2020-09-19 11:49 ` [PATCH bpf-next v7 04/10] bpf: move prog->aux->linked_prog and trampoline into bpf_link on attach Toke Høiland-Jørgensen
2020-09-21 23:05   ` Andrii Nakryiko
2020-09-22 10:17     ` Toke Høiland-Jørgensen
2020-09-22 16:45       ` Andrii Nakryiko
2020-09-22 17:48         ` Toke Høiland-Jørgensen
2020-09-19 11:49 ` [PATCH bpf-next v7 05/10] bpf: support attaching freplace programs to multiple attach points Toke Høiland-Jørgensen
2020-09-21 23:08   ` Andrii Nakryiko
2020-09-19 11:49 ` [PATCH bpf-next v7 06/10] bpf: Fix context type resolving for extension programs Toke Høiland-Jørgensen
2020-09-21 23:09   ` Andrii Nakryiko
2020-09-19 11:49 ` [PATCH bpf-next v7 07/10] libbpf: add support for freplace attachment in bpf_link_create Toke Høiland-Jørgensen
2020-09-21 23:18   ` Andrii Nakryiko
2020-09-19 11:49 ` [PATCH bpf-next v7 08/10] selftests: add test for multiple attachments of freplace program Toke Høiland-Jørgensen
2020-09-21 23:21   ` Andrii Nakryiko
2020-09-19 11:49 ` [PATCH bpf-next v7 09/10] selftests/bpf: Adding test for arg dereference in extension trace Toke Høiland-Jørgensen
2020-09-19 11:49 ` [PATCH bpf-next v7 10/10] selftests: Add selftest for disallowing modify_return attachment to freplace Toke Høiland-Jørgensen
2020-09-21 23:25   ` Andrii Nakryiko
2020-09-21 23:26 ` [PATCH bpf-next v7 00/10] bpf: Support multi-attach for freplace programs Andrii Nakryiko
2020-09-22  9:48   ` Toke Høiland-Jørgensen

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