From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f43.google.com (mail-pj1-f43.google.com [209.85.216.43]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 22B65346FB0 for ; Fri, 19 Jun 2026 19:28:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.43 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781897334; cv=none; b=ULbV79wVcyv7Mi9kTSarTB0KRg7vQgB3u4zuTh08YDNlSoPZ7Ajpuf2/UKdHJATvRrh0s/gEtdVcq8Yd+4SQMebs/ZnqrTsV+zr16T1Jnbbq9+vDXJq4eXSKCfm9gyRbXJsqdO2Ac1r/fnDe3dxWthfFQCF7pt5g7rYAm5BrDTY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781897334; c=relaxed/simple; bh=FlqRMTgwnEYTgwBo0M4QMzzgXOiGkRJeDRkX7I5vYZo=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=oIKmWp/PASNfkwHbG3REvhDfBfY50OeZJg2moYCU8ElE0tP5qOxbsXaQuiryuUUKoQoAXyDCqru+ZUE2DpWbALQrH8fiQv7xh4iAs3SuiWI0aFFZYTtivhmJ0qFm6wV0V3N6bxGrp0d8Di30lJYHNj9UEYH89DnENtOyF+jr+MI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=IU5dTAWH; arc=none smtp.client-ip=209.85.216.43 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="IU5dTAWH" Received: by mail-pj1-f43.google.com with SMTP id 98e67ed59e1d1-36b95eb4bb4so1537609a91.3 for ; Fri, 19 Jun 2026 12:28:53 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1781897332; x=1782502132; darn=vger.kernel.org; h=mime-version:user-agent:content-transfer-encoding:references :in-reply-to:date:cc:to:from:subject:message-id:from:to:cc:subject :date:message-id:reply-to; bh=tdZietZ1vzrwOz+XYJNjMrGChV39Xfbmkh2IyU4ikh0=; b=IU5dTAWHKzT+NpMVAP6hRKK/sKAoftG0M/mm5M/H1j+X4sLT3vGFFGrzOgn+RM8rVV BtrxrsTm4X7szyrrTTDhfanHHQF7HUY2w4q+QJGnOlO3K0RmC+Ok/BNZcybnxzq12ono J7KZK2e7R7ka2iniVazPTLwv3zlwuwcKGSV5u0aMubReFj1vX81fIxrp8ccz7u/e4Yey KeCI9Uy6GFMJheUU6CmhePlFm2tT0QJwl++2V1jZHqO0oJOoGGEET3XaxpgxJXsnC+0S 9XbEjNXTK2z+9qegr4zQeWwgSAneIqbNLqPZ1jXHeN2unmYBcKB6jE/X1TZ0fvOjrh8A fHcg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1781897332; x=1782502132; h=mime-version:user-agent:content-transfer-encoding:references :in-reply-to:date:cc:to:from:subject:message-id:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=tdZietZ1vzrwOz+XYJNjMrGChV39Xfbmkh2IyU4ikh0=; b=D/g6g8WW1r/14PmHE7taBkVRE3T0AGMoaaIbzptd7zRa1alU77egGGpmJC6369vL4l 72De2ZR8xGsOlMhlwo331eqi3uamGIjEfSlQlYKxmP5fZxCDpBNrQHauYsZs5GEHY9TR YvhqLcEypL/a8zJcIHqE7oX/TOosZ1U/VUOsFi2XmHgMYCzyn8JTKXpRYdAQ8+bBdfoU rSbae8+oscfpLQoBLLyFZXUhjxEJ0qAQZSWzXu5r5Pat21OGYQ4LC4uUuI49Zo/h06r1 G64q7ig7PP36eMRFF5jLENNA3Z5mbgV9POvayrv3fJm8PeEc2EWnJWNnsFPAcK0Y6LzE mVsA== X-Forwarded-Encrypted: i=1; AFNElJ/kKTmTE2sICaZHdKXjujDFpYMf8doWfhsfDfIF9h7BmC2WpSKdybGjJw8OQHheHnRBN82f4UmCb6SREWM=@vger.kernel.org X-Gm-Message-State: AOJu0YxCFQELTytH76w8yWcBraEi0lZbC8pJo4qe+JJRQ1Z3VGQArCMH +B/s0zgI2qzyf5GIz3Xe+YBI9pw/odzNye5Pm6/bgX8jBSc3ye+mJ1LM X-Gm-Gg: AfdE7ckZ6f+HSCF/eX3GTR1oEW5RORou01fy4YXhzTTY8dDnUqKZallZRgBZ0BFHgzR JJNg0yQgENnLxjlYLbBsw0+q+wMR0cfo/tkg+uI7P4uG3Wu8/B/6QH+zsDtfHduCHQJSlq/UbB/ dBzkqaxsjbkm/Q0RZEpZOFdSwbsksMzL4rBd/LV6u0udAf0glud0aOFs2jLoLSWkQO7VB20ga7D KUUa+Kwl/PWH9MEFElc4r9jW42/KYJ2IpuEy4JXWfLuQL0Lhf1oQdJp2QM4MFUSDFU/Rc5/zryH CWkypLHb7E7utwVBeBBtybSoumqvDPAYFywOH1eF2YZ9QPkRq4qmFK98jg2vX4iqIjcpJqhnH3u yTdkMFdDFy4loge1/h7gkVVcb6tsTufKjiORXuuxWEU/aujXRmWyqN8y4wl1Z3UI3sOx5lih3rX 7lBFz6ARo87uBW87Iq1qGsfFPEnRQ9R2j9ghNDtlvqNg== X-Received: by 2002:a17:90b:4a90:b0:366:10f1:3d91 with SMTP id 98e67ed59e1d1-37d160bec36mr4958120a91.1.1781897332384; Fri, 19 Jun 2026 12:28:52 -0700 (PDT) Received: from [192.168.0.226] ([38.34.87.7]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-37d4f225870sm363308a91.8.2026.06.19.12.28.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 19 Jun 2026 12:28:51 -0700 (PDT) Message-ID: <5986dad827772fb0060f7c4adfb811ad93755a52.camel@gmail.com> Subject: Re: [PATCH bpf-next 1/2] bpf: Reject offset refcount acquire arguments From: Eduard Zingerman To: Yiyang Chen , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Kumar Kartikeya Dwivedi Cc: John Fastabend , Martin KaFai Lau , Song Liu , Yonghong Song , Jiri Olsa , Emil Tsalapatis , Shuah Khan , Viktor Malik , Leon Hwang , Dave Marchevsky , bpf@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Date: Fri, 19 Jun 2026 12:28:48 -0700 In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.60.1 (3.60.1-1.fc44) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Fri, 2026-06-19 at 07:59 +0000, Yiyang Chen wrote: > bpf_refcount_acquire() increments the refcount at the caller-supplied > pointer plus the refcount field offset, then returns the caller-supplied > pointer unchanged. >=20 > The verifier records the return value as a base pointer to the refcounted > object. >=20 > bpf_list_pop_front() and bpf_rbtree_remove() can return embedded graph-no= de > pointers as PTR_TO_BTF_ID | MEM_ALLOC with a fixed offset equal to the no= de > field offset. Passing such a pointer directly to bpf_refcount_acquire() > currently passes the refcounted-kptr type check. >=20 > That makes the runtime operation start from base + node_off while the > verifier models the returned pointer as the object base. >=20 > Require refcount-acquire arguments to have zero offset. Programs can stil= l > acquire a refcount from a graph-node-derived pointer after normalizing it > with container_of(). >=20 > Fixes: 7c50b1cb76aca ("bpf: Add bpf_refcount_acquire kfunc") > Signed-off-by: Yiyang Chen > --- Hi Yiyang, thank you for the bug report. > kernel/bpf/verifier.c | 5 +++++ > 1 file changed, 5 insertions(+) >=20 > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c > index 2abc79dbf..4510fe0b4 100644 > --- a/kernel/bpf/verifier.c > +++ b/kernel/bpf/verifier.c > @@ -12392,6 +12392,11 @@ static int check_kfunc_args(struct bpf_verifier_= env *env, struct bpf_kfunc_call_ > reg_arg_name(env, argno)); > return -EINVAL; > } > + if (reg->var_off.value !=3D 0) { I think this check should be handled by check_func_arg_reg_off() / __check_ptr_off_reg(), could you please reorganize the code such that it is handled there? > + verbose(env, "%s must have zero offset when passed to %s\n", > + reg_arg_name(env, argno), meta->func_name); > + return -EINVAL; > + } > if (!type_is_non_owning_ref(reg->type)) > meta->arg_owning_ref =3D true; > =20