linux-kernel - Re: [PATCH bpf-next] bpf: use type_may_be_null() helper for nullable-param check

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Message-ID: <2911a33d8c9f408cc8d5863c54ea0ad1eba5de38.camel@gmail.com>
Date: Thu, 05 Sep 2024 12:08:49 -0700
From: Eduard Zingerman <eddyz87@...il.com>
To: Shung-Hsi Yu <shung-hsi.yu@...e.com>, bpf@...r.kernel.org
Cc: Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann
 <daniel@...earbox.net>,  Andrii Nakryiko <andrii@...nel.org>, Martin KaFai
 Lau <martin.lau@...ux.dev>, Song Liu <song@...nel.org>,  Yonghong Song
 <yonghong.song@...ux.dev>, John Fastabend <john.fastabend@...il.com>, KP
 Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...ichev.me>, Hao Luo
 <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>, "David S. Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski
 <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, David Vernet
 <void@...ifault.com>, netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
  kernel test robot <lkp@...el.com>
Subject: Re: [PATCH bpf-next] bpf: use type_may_be_null() helper for
 nullable-param check

On Thu, 2024-09-05 at 13:52 +0800, Shung-Hsi Yu wrote:
> Commit 980ca8ceeae6 ("bpf: check bpf_dummy_struct_ops program params for
> test runs") does bitwise AND between reg_type and PTR_MAYBE_NULL, which
> is correct, but due to type difference the compiler complains:
> 
>   net/bpf/bpf_dummy_struct_ops.c:118:31: warning: bitwise operation between different enumeration types ('const enum bpf_reg_type' and 'enum bpf_type_flag') [-Wenum-enum-conversion]
>     118 |                 if (info && (info->reg_type & PTR_MAYBE_NULL))
>         |                              ~~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~~~
> 
> Workaround the warning by moving the type_may_be_null() helper from
> verifier.c into bpf_verifier.h, and reuse it here to check whether param
> is nullable.
> 
> Fixes: 980ca8ceeae6 ("bpf: check bpf_dummy_struct_ops program params for test runs")
> Reported-by: kernel test robot <lkp@...el.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202404241956.HEiRYwWq-lkp@intel.com/
> Signed-off-by: Shung-Hsi Yu <shung-hsi.yu@...e.com>
> ---

Thank you for this fix.
Replacing other uses of PTR_MAYBE_NULL suggested by Matt seems like a
good idea, but it does not preclude merge for this patch.

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

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