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

[Blaise Boscaccy <bboscaccy@linux.microsoft.com>]

Alexei Starovoitov <alexei.starovoitov@gmail.com> writes:

> On Tue, Feb 25, 2025 at 11:06 PM Song Liu <song@kernel.org> wrote:
>>
>> On Tue, Feb 25, 2025 at 4:31 PM Blaise Boscaccy
>> <bboscaccy@linux.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"?
>
> +1
> Just passing the bool should do.
> Passing uattr is a footgun. Last thing we need is to open up TOCTOU concerns.

Sounds good to me, I'll rework it to use a bool instead.

-blaise