Re: [PATCH bpf v2 1/2] bpf: link: refuse non-O_RDWR flags in BPF_OBJ_GET

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On Wed, Mar 31, 2021 at 7:04 AM Lorenz Bauer <lmb@xxxxxxxxxxxxxx> wrote:
>
> On Fri, 26 Mar 2021 at 16:05, Lorenz Bauer <lmb@xxxxxxxxxxxxxx> wrote:
> >
> > Invoking BPF_OBJ_GET on a pinned bpf_link checks the path access
> > permissions based on file_flags, but the returned fd ignores flags.
> > This means that any user can acquire a "read-write" fd for a pinned
> > link with mode 0664 by invoking BPF_OBJ_GET with BPF_F_RDONLY in
> > file_flags. The fd can be used to invoke BPF_LINK_DETACH, etc.
> >
> > Fix this by refusing non-O_RDWR flags in BPF_OBJ_GET. This works
> > because OBJ_GET by default returns a read write mapping and libbpf
> > doesn't expose a way to override this behaviour for programs
> > and links.
>
> Hi Alexei and Daniel,
>
> I think these two patches might have fallen through the cracks, could
> you take a look? I'm not sure what the etiquette is around bumping a
> set, so please let me know if you'd prefer me to send the patches with
> acks included or something like that.

It is still in patchworks. I didn't have time to think it through.
Sorry for delay.



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