From: Yonghong Song <yhs@meta.com>
To: Krister Johansen <kjlx@templeofstupid.com>, bpf@vger.kernel.org
Cc: Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Martin KaFai Lau <martin.lau@linux.dev>,
Song Liu <song@kernel.org>, Yonghong Song <yhs@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@kernel.org>,
Stanislav Fomichev <sdf@google.com>, Hao Luo <haoluo@google.com>,
Jiri Olsa <jolsa@kernel.org>, Mykola Lysenko <mykolal@fb.com>,
Shuah Khan <shuah@kernel.org>,
linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org
Subject: Re: [PATCH bpf v3 1/2] bpf: ensure main program has an extable
Date: Thu, 8 Jun 2023 20:33:55 -0700 [thread overview]
Message-ID: <b877e130-2a81-7233-3162-4f414b58549e@meta.com> (raw)
In-Reply-To: <d0c703a2d47d3368032c65fa70297cdcb5a16da7.1686268304.git.kjlx@templeofstupid.com>
On 6/8/23 5:10 PM, Krister Johansen wrote:
> When subprograms are in use, the main program is not jit'd after the
> subprograms because jit_subprogs sets a value for prog->bpf_func upon
> success. Subsequent calls to the JIT are bypassed when this value is
> non-NULL. This leads to a situation where the main program and its
> func[0] counterpart are both in the bpf kallsyms tree, but only func[0]
> has an extable. Extables are only created during JIT. Now there are
> two nearly identical program ksym entries in the tree, but only one has
> an extable. Depending upon how the entries are placed, there's a chance
> that a fault will call search_extable on the aux with the NULL entry.
>
> Since jit_subprogs already copies state from func[0] to the main
> program, include the extable pointer in this state duplication.
> Additionally, ensure that the copy of the main program in func[0] is not
> added to the bpf_prog_kallsyms table. Instead, let the main program get
> added later in bpf_prog_load(). This ensures there is only a single
> copy of the main program in the kallsyms table, and that its tag matches
> the tag observed by tooling like bpftool.
>
> Cc: stable@vger.kernel.org
> Fixes: 1c2a088a6626 ("bpf: x64: add JIT support for multi-function programs")
> Signed-off-by: Krister Johansen <kjlx@templeofstupid.com>
Acked-by: Yonghong Song <yhs@fb.com>
next prev parent reply other threads:[~2023-06-09 3:34 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-09 0:10 [PATCH bpf v3 0/2] bpf: fix NULL dereference during extable search Krister Johansen
2023-06-09 0:10 ` [PATCH bpf v3 1/2] bpf: ensure main program has an extable Krister Johansen
2023-06-09 3:33 ` Yonghong Song [this message]
2023-06-09 0:11 ` [PATCH bpf v3 2/2] selftests/bpf: add a test for subprogram extables Krister Johansen
2023-06-09 3:52 ` Yonghong Song
2023-06-09 21:34 ` Krister Johansen
2023-06-09 18:15 ` Alexei Starovoitov
2023-06-09 19:08 ` Krister Johansen
2023-06-12 13:46 ` Ilya Leoshkevich
2023-06-12 22:07 ` Alexei Starovoitov
2023-06-12 22:12 ` Krister Johansen
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