netdev - Re: [PATCH net-next 1/2] bpf: save extended inner map info for percpu array maps as well

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Message-ID: <CAADnVQLg4zcS99=bCLgczZWCTbUwRXyyoTFC+_LU08rQ1_EbZQ@mail.gmail.com>
Date: Wed, 15 May 2024 09:55:37 -0700
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Andrii Nakryiko <andrii@...nel.org>
Cc: Network Development <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>, 
	Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
	Martin KaFai Lau <martin.lau@...nel.org>, Linus Torvalds <torvalds@...ux-foundation.org>, 
	Jakub Kicinski <kuba@...nel.org>
Subject: Re: [PATCH net-next 1/2] bpf: save extended inner map info for percpu
 array maps as well

On Tue, May 14, 2024 at 11:24 PM Andrii Nakryiko <andrii@...nel.org> wrote:
>
> ARRAY_OF_MAPS and HASH_OF_MAPS map types have special logic to save
> a few extra fields required for correct operations of ARRAY maps, when
> they are used as inner maps. PERCPU_ARRAY maps have similar
> requirements as they now support generating inline element lookup
> logic. So make sure that both classes of maps are handled correctly.
>
> Reported-by: Jakub Kicinski <kuba@...nel.org>
> Fixes: db69718b8efa ("bpf: inline bpf_map_lookup_elem() for PERCPU_ARRAY maps")
> Signed-off-by: Andrii Nakryiko <andrii@...nel.org>
> ---
>  kernel/bpf/map_in_map.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/bpf/map_in_map.c b/kernel/bpf/map_in_map.c
> index 8ef269e66ba5..b4f18c85d7bc 100644
> --- a/kernel/bpf/map_in_map.c
> +++ b/kernel/bpf/map_in_map.c
> @@ -32,7 +32,7 @@ struct bpf_map *bpf_map_meta_alloc(int inner_map_ufd)
>
>         inner_map_meta_size = sizeof(*inner_map_meta);
>         /* In some cases verifier needs to access beyond just base map. */
> -       if (inner_map->ops == &array_map_ops)
> +       if (inner_map->ops == &array_map_ops || inner_map->ops == &percpu_array_map_ops)
>                 inner_map_meta_size = sizeof(struct bpf_array);

Applied the fix to stop the bleeding,
but we need to fix this fragility long term.