From patchwork Thu Mar 13 17:41:46 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Luis Gerhorst X-Patchwork-Id: 873697 Received: from mx-rz-2.rrze.uni-erlangen.de (mx-rz-2.rrze.uni-erlangen.de [131.188.11.21]) (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 6987E1DC985; Thu, 13 Mar 2025 17:47:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=131.188.11.21 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741888052; cv=none; b=qyjtb14NWGQaBsThB2CLK2+1aqr2RH69L8CZh4CXJomOCMcY5BOwyeY1sskkhn2bMMObuBhxmUDRLvMf8XNcJZjmvXd6VMn/zjF9WughKlltQ+N8aNnAd4iq/Nb9HkF+WquRT6JvEvx89qgDFEJIf8CI7RozNpVWVevbwRBzTMM= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741888052; c=relaxed/simple; bh=3hd8lSEntiMzBU02Jl7UN2LoMudSHfYGNrN8n6SPVhM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=gpgBIM+kRXn100t/1GMS29Bn4TEzaGzP7eD+NHEoavihgKSXKwq97fIPXTDReVpVW5JT/aWX91mFrRpgob9tlxYsOwG4xz2CVlMEaL6RcQ4IJbDEY16O3cCJaSy5fodCD97EOewSI2Nzv9osxbXIb44SH2SHCkn7mp9XJP4rdB4= 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=OdzuV4hB; arc=none smtp.client-ip=131.188.11.21 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="OdzuV4hB" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fau.de; s=fau-2021; t=1741888048; bh=7PdRevp9VEBQ7cXe+7SQLSfTFULBTjgQdqLzMbVqv7w=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From:To:CC: Subject; b=OdzuV4hBjdperRm0XJOh2lk2Vh3TaWgTXirNqf6btIxTKqUuKQKbTti196BtDLE10 EnabT2TpBViOZFl85SCJ1WvXDOol1iuY6w03mEIp6YkmJqocIposjTAfU16QJXS1+G AJHYYnLfFHCrGKq28gmAUkKY6dJ5MGc4HhQBlS4p6gSFVljkCJues9EtLy1Y5uoNUG WttBODYXpemaNkvZGyqiZeQPst1vL5+NRYIcsvc3XeS20HpsCPs47y5pYHVn7FXpxZ OE55JosgXUbJcSYolp3bzaq13u+V4AhOrx5B6sW544da05jdcZlxTDqUIdXAiRD8LD k1RZLnKf1flFg== 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-2.rrze.uni-erlangen.de (Postfix) with ESMTPS id 4ZDFM40SxpzPjxV; Thu, 13 Mar 2025 18:47:28 +0100 (CET) X-Virus-Scanned: amavisd-new at boeck5.rrze.uni-erlangen.de (RRZE) X-RRZE-Flag: Not-Spam X-RRZE-Submit-IP: 2001:9e8:3614:2b00:7ee6:68e5:4447:ba92 Received: from luis-tp.fritz.box (unknown [IPv6:2001:9e8:3614:2b00:7ee6:68e5:4447:ba92]) (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: U2FsdGVkX18m9Vn9FOlTwMXhkaYiMwSCy8dUUwAZyWw=) by smtp-auth.uni-erlangen.de (Postfix) with ESMTPSA id 4ZDFM03tYpzPjvW; Thu, 13 Mar 2025 18:47:24 +0100 (CET) From: Luis Gerhorst To: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Puranjay Mohan , Xu Kuohai , Catalin Marinas , Will Deacon , Hari Bathini , Christophe Leroy , Naveen N Rao , Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , Mykola Lysenko , Shuah Khan , Luis Gerhorst , Henriette Herzog , Cupertino Miranda , Matan Shachnai , Dimitar Kanaliev , Shung-Hsi Yu , Daniel Xu , bpf@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-kselftest@vger.kernel.org, George Guo , WANG Xuerui , Tiezhu Yang Cc: Maximilian Ott , Milan Stephan Subject: [PATCH bpf-next 08/11] bpf: Allow nospec-protected var-offset stack access Date: Thu, 13 Mar 2025 18:41:46 +0100 Message-ID: <20250313174149.1113165-3-luis.gerhorst@fau.de> X-Mailer: git-send-email 2.48.1 In-Reply-To: <20250313174149.1113165-1-luis.gerhorst@fau.de> References: <20250313172127.1098195-1-luis.gerhorst@fau.de> <20250313174149.1113165-1-luis.gerhorst@fau.de> Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Insert a nospec before the access to prevent it from ever using an index that is subject to speculative scalar-confusion. Signed-off-by: Luis Gerhorst Acked-by: Henriette Herzog Cc: Maximilian Ott Cc: Milan Stephan --- kernel/bpf/verifier.c | 24 ++++++++++++------------ 1 file changed, 12 insertions(+), 12 deletions(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 8093a5bac4d1..683a76aceffa 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -7858,6 +7858,11 @@ static int check_atomic(struct bpf_verifier_env *env, struct bpf_insn *insn) } } +static struct bpf_insn_aux_data *cur_aux(const struct bpf_verifier_env *env) +{ + return &env->insn_aux_data[env->insn_idx]; +} + /* When register 'regno' is used to read the stack (either directly or through * a helper function) make sure that it's within stack boundary and, depending * on the access type and privileges, that all elements of the stack are @@ -7897,18 +7902,18 @@ static int check_stack_range_initialized( if (tnum_is_const(reg->var_off)) { min_off = max_off = reg->var_off.value + off; } else { - /* Variable offset is prohibited for unprivileged mode for + /* Variable offset requires a nospec for unprivileged mode for * simplicity since it requires corresponding support in * Spectre masking for stack ALU. * See also retrieve_ptr_limit(). */ if (!env->bypass_spec_v1) { - char tn_buf[48]; - - tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off); - verbose(env, "R%d variable offset stack access prohibited for !root, var_off=%s\n", - regno, tn_buf); - return -EACCES; + /* Allow the access, but prevent it from using a + * speculative offset using a nospec before the + * dereference op. + */ + cur_aux(env)->nospec = true; + WARN_ON_ONCE(cur_aux(env)->alu_state); } /* Only initialized buffer on stack is allowed to be accessed * with variable offset. With uninitialized buffer it's hard to @@ -11096,11 +11101,6 @@ static int check_get_func_ip(struct bpf_verifier_env *env) return -ENOTSUPP; } -static struct bpf_insn_aux_data *cur_aux(const struct bpf_verifier_env *env) -{ - return &env->insn_aux_data[env->insn_idx]; -} - static bool loop_flag_is_zero(struct bpf_verifier_env *env) { struct bpf_reg_state *regs = cur_regs(env);