linux-kernel - Re: [PATCH 1/1] security: Propagate universal pointer data in bpf hooks

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Message-ID: <CAPhsuW7=uALYiLfKfApvSG0V+RV+M20w5x3myTZVLNRyYnBFnQ@mail.gmail.com>
Date: Tue, 25 Feb 2025 23:06:29 -0800
From: Song Liu <song@...nel.org>
To: Blaise Boscaccy <bboscaccy@...ux.microsoft.com>
Cc: Paul Moore <paul@...l-moore.com>, James Morris <jmorris@...ei.org>, 
	"Serge E. Hallyn" <serge@...lyn.com>, Alexei Starovoitov <ast@...nel.org>, 
	Daniel Borkmann <daniel@...earbox.net>, John Fastabend <john.fastabend@...il.com>, 
	Andrii Nakryiko <andrii@...nel.org>, Martin KaFai Lau <martin.lau@...ux.dev>, 
	Eduard Zingerman <eddyz87@...il.com>, Yonghong Song <yonghong.song@...ux.dev>, 
	KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, 
	Jiri Olsa <jolsa@...nel.org>, Stephen Smalley <stephen.smalley.work@...il.com>, 
	Ondrej Mosnacek <omosnace@...hat.com>, linux-security-module@...r.kernel.org, 
	linux-kernel@...r.kernel.org, bpf@...r.kernel.org, selinux@...r.kernel.org
Subject: Re: [PATCH 1/1] security: Propagate universal pointer data in bpf hooks

On Tue, Feb 25, 2025 at 4:31 PM Blaise Boscaccy
<bboscaccy@...ux.microsoft.com> wrote:
>
> Certain bpf syscall subcommands are available for usage from both
> userspace and the kernel. LSM modules or eBPF gatekeeper programs may
> need to take a different course of action depending on whether or not
> a BPF syscall originated from the kernel or userspace.
>
> Additionally, some of the bpf_attr struct fields contain pointers to
> arbitrary memory. Currently the functionality to determine whether or
> not a pointer refers to kernel memory or userspace memory is exposed
> to the bpf verifier, but that information is missing from various LSM
> hooks.
>
> Here we augment the LSM hooks to provide this data, by simply passing
> the corresponding universal pointer in any hook that contains already
> contains a bpf_attr struct that corresponds to a subcommand that may
> be called from the kernel.

I think this information is useful for LSM hooks.

Question: Do we need a full bpfptr_t for these hooks, or just a boolean
"is_kernel or not"?

Thanks,
Song

> Signed-off-by: Blaise Boscaccy <bboscaccy@...ux.microsoft.com>