From nobody Sat Oct 11 00:25:21 2025 Received: from mx-rz-1.rrze.uni-erlangen.de (mx-rz-1.rrze.uni-erlangen.de [131.188.11.20]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E7AC91BD9CE; Wed, 11 Jun 2025 21:23:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=131.188.11.20 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749677039; cv=none; b=bulC0PajIt2khmUIQghsRSLVKqwkKS3fdZQKeKGs4Zg7ZWkBWYd/ej67pLHg8W8yyui0f+UVMzzzbxfSI9FyhX7JiFfnzGL0823U3MTj5SScqF7HF4WYXltBrTFkOFiv+weTDQhnnn8ZfgDaDqe0ZHq0RmBMfikUQCkeijfNU5k= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749677039; c=relaxed/simple; bh=t1zJH4Rmm4htAzj/dQwNCS9TEe1c1gCbgRoNZ2a76h4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=pmjGXMk3QCKFgFTT68iAmRpIwKmw34sleU895c+CEsdg15rSKJJqlR+aB62ooiKlYt6qxQISHckIahuxK1gE55QH1o3NNUs9PUUuxiLBRZ9aJMVJtqnnEzk/047LEXygW8m46lQTewkpHDYyQocm1SSt3rmJW/RFsLiKtzgfQak= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=fau.de; spf=pass smtp.mailfrom=fau.de; dkim=pass (2048-bit key) header.d=fau.de header.i=@fau.de header.b=GB7QRGZ5; arc=none smtp.client-ip=131.188.11.20 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=fau.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=fau.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=fau.de header.i=@fau.de header.b="GB7QRGZ5" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fau.de; s=fau-2021; t=1749676562; bh=S2j0xHEZeQOTVtx7TJX88U0NbtEMbxvs08E3DcOiM3k=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From:To:CC: Subject; b=GB7QRGZ5lNQDix0fSkRgtNjMUUycMz/UHj26osAKdXgqXZKpzhvC7+v9XyS8QmlYC azUB/LpaFU0XoJC/mJ0vbZ/D59tDhDxJBssj5jaqn1fbH695ZHK/xkgYdQIE7kK+sS N5j8WALlbhpLQrq98pYbzkDR7mjZlqOt+NDyWZyph3hi749A9BIreU1ETu6Pg/Pma7 QZXaBnZdUvryQAzJbNaE60AG/8ryVYMTcyp52o6CfoGab8AYoxvbeVrnlVBXMvDLHI OyijBtu3r24T5wMOIZBqjwlbpMaG3cg0dUtM4NFqKqTy0xGay1OeXO7hnwnR+7souS uQpsPOkO1Iuxg== Received: from mx-rz-smart.rrze.uni-erlangen.de (mx-rz-smart.rrze.uni-erlangen.de [IPv6:2001:638:a000:1025::1e]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-rz-1.rrze.uni-erlangen.de (Postfix) with ESMTPS id 4bHdkB0q3Sz8sk1; Wed, 11 Jun 2025 23:16:02 +0200 (CEST) X-Virus-Scanned: amavisd-new at boeck1.rrze.uni-erlangen.de (RRZE) X-RRZE-Flag: Not-Spam X-RRZE-Submit-IP: 2001:9e8:3626:500:39da:8819:39bd:1255 Received: from luis-tp.fritz.box (unknown [IPv6:2001:9e8:3626:500:39da:8819:39bd:1255]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: U2FsdGVkX19Vu+9xQHHGMkmfqtW7CJMHQ2bOqLm6aCk=) by smtp-auth.uni-erlangen.de (Postfix) with ESMTPSA id 4bHdk70Msdz8spC; Wed, 11 Jun 2025 23:15:58 +0200 (CEST) From: Luis Gerhorst To: Alexei Starovoitov , Daniel Borkmann , John Fastabend , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Song Liu , Yonghong Song , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , bpf@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Luis Gerhorst Subject: [PATCH bpf-next] bpf: Remove redundant free_verifier_state()/pop_stack() Date: Wed, 11 Jun 2025 23:14:31 +0200 Message-ID: <20250611211431.275731-1-luis.gerhorst@fau.de> X-Mailer: git-send-email 2.49.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" This patch removes duplicated code. Eduard points out [1]: Same cleanup cycles are done in push_stack() and push_async_cb(), both functions are only reachable from do_check_common() via do_check() -> do_check_insn(). Hence, I think that cur state should not be freed in push_*() functions and pop_stack() loop there is not needed. This would also fix the 'symptom' for [2], but the issue also has a simpler fix which was sent separately. This fix also makes sure the push_*() callers always return an error for which error_recoverable_with_nospec(err) is false. This is required because otherwise we try to recover and access the stale `state`. [1] https://lore.kernel.org/all/b6931bd0dd72327c55287862f821ca6c4c3eb69a.ca= mel@gmail.com/ [2] https://lore.kernel.org/all/68497853.050a0220.33aa0e.036a.GAE@google.co= m/ Reported-by: Eduard Zingerman Link: https://lore.kernel.org/all/b6931bd0dd72327c55287862f821ca6c4c3eb69a.= camel@gmail.com/ Signed-off-by: Luis Gerhorst Acked-by: Eduard Zingerman --- kernel/bpf/verifier.c | 26 +++++++++++--------------- 1 file changed, 11 insertions(+), 15 deletions(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index d3bff0385a55..fa147c207c4b 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -2066,10 +2066,10 @@ static struct bpf_verifier_state *push_stack(struct= bpf_verifier_env *env, } return &elem->st; err: - free_verifier_state(env->cur_state, true); - env->cur_state =3D NULL; - /* pop all elements and return */ - while (!pop_stack(env, NULL, NULL, false)); + /* free_verifier_state() and pop_stack() loop will be done in + * do_check_common(). Caller must return an error for which + * error_recoverable_with_nospec(err) is false. + */ return NULL; } =20 @@ -2838,10 +2838,10 @@ static struct bpf_verifier_state *push_async_cb(str= uct bpf_verifier_env *env, elem->st.frame[0] =3D frame; return &elem->st; err: - free_verifier_state(env->cur_state, true); - env->cur_state =3D NULL; - /* pop all elements and return */ - while (!pop_stack(env, NULL, NULL, false)); + /* free_verifier_state() and pop_stack() loop will be done in + * do_check_common(). Caller must return an error for which + * error_recoverable_with_nospec(err) is false. + */ return NULL; } =20 @@ -22904,13 +22904,9 @@ static int do_check_common(struct bpf_verifier_env= *env, int subprog) =20 ret =3D do_check(env); out: - /* check for NULL is necessary, since cur_state can be freed inside - * do_check() under memory pressure. - */ - if (env->cur_state) { - free_verifier_state(env->cur_state, true); - env->cur_state =3D NULL; - } + WARN_ON_ONCE(!env->cur_state); + free_verifier_state(env->cur_state, true); + env->cur_state =3D NULL; while (!pop_stack(env, NULL, NULL, false)); if (!ret && pop_log) bpf_vlog_reset(&env->log, 0); base-commit: 1d251153a480fc7467d00a8c5dabc55cc6166c43 --=20 2.49.0