Re: [PATCH bpf-next] libbpf: fix bpf_object__open_skeleton()'s mishandling of options

[Eduard Zingerman <eddyz87@gmail.com>]

On Tue, 2024-08-27 at 13:37 -0700, Andrii Nakryiko wrote:
> We do an ugly copying of options in bpf_object__open_skeleton() just to
> be able to set object name from skeleton's recorded name (while still
> allowing user to override it through opts->object_name).
> 
> This is not just ugly, but it also is broken due to memcpy() that
> doesn't take into account potential skel_opts' and user-provided opts'
> sizes differences due to backward and forward compatibility. This leads
> to copying over extra bytes and then failing to validate options
> properly. It could, technically, lead also to SIGSEGV, if we are unlucky.
> 
> So just get rid of that memory copy completely and instead pass
> default object name into bpf_object_open() directly, simplifying all
> this significantly. The rule now is that obj_name should be non-NULL for
> bpf_object_open() when called with in-memory buffer, so validate that
> explicitly as well.
> 
> We adopt bpf_object__open_mem() to this as well and generate default
> name (based on buffer memory address and size) outside of bpf_object_open().
> 
> Fixes: d66562fba1ce ("libbpf: Add BPF object skeleton support")
> Reported-by: Daniel Müller <deso@posteo.net>
> Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
> ---

Acked-by: Eduard Zingerman <eddyz87@gmail.com>

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