From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Hao Luo <haoluo@google.com>
Cc: Alexei Starovoitov <ast@kernel.org>,
Andrii Nakryiko <andrii@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
Yonghong Song <yhs@fb.com>, KP Singh <kpsingh@kernel.org>,
bpf <bpf@vger.kernel.org>
Subject: Re: [PATCH bpf-next v2 8/9] bpf: Add MEM_RDONLY for helper args that are pointers to rdonly mem.
Date: Sat, 18 Dec 2021 13:48:52 -0800 [thread overview]
Message-ID: <CAADnVQLYrP0P5CZj1domV3n3oHJsDYRbbk+1tym223-Z=Tk54A@mail.gmail.com> (raw)
In-Reply-To: <20211217003152.48334-9-haoluo@google.com>
On Thu, Dec 16, 2021 at 4:32 PM Hao Luo <haoluo@google.com> wrote:
>
> Some helper functions may modify its arguments, for example,
> bpf_d_path, bpf_get_stack etc. Previously, their argument types
> were marked as ARG_PTR_TO_MEM, which is compatible with read-only
> mem types, such as PTR_TO_RDONLY_BUF. Therefore it's legitimate
> to modify a read-only memory by passing it into one of such helper
> functions.
I've added ", but technically incorrect" to the above sentence.
Otherwise it sounds like it was an ok thing to do.
I've considered adding a set of Fixes tag, but there would be too many
and it's a laborious task to look through all such helpers just
to beautify the commit log. This patch set isn't going to
be backported anyway due to complexity.
Please add a test to make sure that bpf_d_path on rdonly buf
is rejected.
Thank you very much for doing this work.
It's a great improvement to the verifier type handling.
There is a concern that generality of flags may cause
a regression, but no amount of code review will reveal that.
Please watch out for strange verifier issues.
next prev parent reply other threads:[~2021-12-18 21:49 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-17 0:31 [PATCH bpf-next v2 0/9] Introduce composable bpf types Hao Luo
2021-12-17 0:31 ` [PATCH bpf-next v2 1/9] bpf: Introduce composable reg, ret and arg types Hao Luo
2021-12-17 0:31 ` [PATCH bpf-next v2 2/9] bpf: Replace ARG_XXX_OR_NULL with ARG_XXX | PTR_MAYBE_NULL Hao Luo
2021-12-17 0:31 ` [PATCH bpf-next v2 3/9] bpf: Replace RET_XXX_OR_NULL with RET_XXX " Hao Luo
2021-12-17 0:31 ` [PATCH bpf-next v2 4/9] bpf: Replace PTR_TO_XXX_OR_NULL with PTR_TO_XXX " Hao Luo
2021-12-18 21:48 ` Alexei Starovoitov
2021-12-17 0:31 ` [PATCH bpf-next v2 5/9] bpf: Introduce MEM_RDONLY flag Hao Luo
2021-12-17 0:31 ` [PATCH bpf-next v2 6/9] bpf: Convert PTR_TO_MEM_OR_NULL to composable types Hao Luo
2021-12-17 0:31 ` [PATCH bpf-next v2 7/9] bpf: Make per_cpu_ptr return rdonly PTR_TO_MEM Hao Luo
2021-12-18 21:48 ` Alexei Starovoitov
2021-12-17 0:31 ` [PATCH bpf-next v2 8/9] bpf: Add MEM_RDONLY for helper args that are pointers to rdonly mem Hao Luo
2021-12-18 21:48 ` Alexei Starovoitov [this message]
2021-12-20 20:14 ` Hao Luo
2021-12-17 0:31 ` [PATCH bpf-next v2 9/9] bpf/selftests: Test PTR_TO_RDONLY_MEM Hao Luo
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