From patchwork Wed Aug 23 02:07:02 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yafang Shao X-Patchwork-Id: 13361555 X-Patchwork-Delegate: bpf@iogearbox.net Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (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 390E715BC for ; Wed, 23 Aug 2023 02:07:10 +0000 (UTC) Received: from mail-oo1-xc35.google.com (mail-oo1-xc35.google.com [IPv6:2607:f8b0:4864:20::c35]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 88408E4A; Tue, 22 Aug 2023 19:07:08 -0700 (PDT) Received: by mail-oo1-xc35.google.com with SMTP id 006d021491bc7-570c51530e5so2077997eaf.3; Tue, 22 Aug 2023 19:07:08 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20221208; t=1692756428; x=1693361228; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=mU5FNyFto872iS/tgMcoUPNuBwmFiNSaWS6P6+DDA0A=; b=bqPT7KEGvEt18ZuX9+5swBL7588zuwbuMEViBE41KMRQ6MdDCO0QThdph7lElc9zNZ 3Ymtv4PjGYjWE42q4cLbs4SCuRKlxUN4kle+V0k2jEh/yxkck+re40e7ob0uDCON8Smw oWUObyw22V2bAFc+Yc9RCKpq63fbmfkQk6mLaN57sAO64ZPsvhLHWzS9ucZuwtPC5efi SQ8E0qzMfrAVEskFvIFUJIPByQNbAL5L/XxXWM+fwcuGrtWB14jUYTPyRn4Z6AWVM2WI +CeFdaGw87X+O4l3CU9yaQ3qzr7PCPEDqBEZVklu+WpGHlHAajedKjClKH3fz4sIi3Xd pUdQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1692756428; x=1693361228; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=mU5FNyFto872iS/tgMcoUPNuBwmFiNSaWS6P6+DDA0A=; b=RVOEL2VppRh4TcQXOk+pHyzcYj/R5iS9Wi+4r+PrR6RDl7BJTzIV3f0mlaas6LUPN/ yVaNDk4BHyjdMfzXPdrI9KLerFl4Qw17+l5C//zc5b7f/0CdGkR+oz1/0RAXJwOLLJi0 ZxJWxr1n2o5ceVYxjBccQ6iyduVYDLjB++6p0BBUaPDENZLSVCQ+ArY6P2MhV77XbFqE YbN2abK1Vi6rCGgMSLp1KX1ZNpMqvhhg2lXaoFuI3sUmb1FQ2Q5NcrOO9DdVlo/61hqb iWxsWtJ8ruLd8lO05lFnNCTExT2CamL4jeH42q7EZ5JwLMoqimEyQgnRIniUw7bu8+Xg /Ihg== X-Gm-Message-State: AOJu0YyOWGk2siv3AX8IUsY7Qkrc9TRz4M773iCgBipZCksS0Eg9zLo8 3tq6MWE2bBdEu/usG3t7tPMwtn7xOqYcNg+0 X-Google-Smtp-Source: AGHT+IEeK3Vu67X8WCCYwtmrQ+ZC4f647aPpKtj9+3HlQa7BuPidkBfHgPUcMNKxzbhjH7bgJmpn9A== X-Received: by 2002:a05:6358:2608:b0:134:c785:5932 with SMTP id l8-20020a056358260800b00134c7855932mr10335787rwc.32.1692756427789; Tue, 22 Aug 2023 19:07:07 -0700 (PDT) Received: from vultr.guest ([149.28.193.116]) by smtp.gmail.com with ESMTPSA id y15-20020aa7804f000000b0064f7c56d8b7sm8313627pfm.219.2023.08.22.19.07.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 22 Aug 2023 19:07:07 -0700 (PDT) From: Yafang Shao To: ast@kernel.org, daniel@iogearbox.net, john.fastabend@gmail.com, andrii@kernel.org, martin.lau@linux.dev, song@kernel.org, yonghong.song@linux.dev, kpsingh@kernel.org, sdf@google.com, haoluo@google.com, jolsa@kernel.org, eddyz87@gmail.com Cc: bpf@vger.kernel.org, Yafang Shao , Alexei Starovoitov , stable@vger.kernel.org Subject: [PATCH v2 bpf-next 1/2] bpf: Fix issue in verifying allow_ptr_leaks Date: Wed, 23 Aug 2023 02:07:02 +0000 Message-Id: <20230823020703.3790-2-laoar.shao@gmail.com> X-Mailer: git-send-email 2.39.3 In-Reply-To: <20230823020703.3790-1-laoar.shao@gmail.com> References: <20230823020703.3790-1-laoar.shao@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_FROM, RCVD_IN_DNSWL_BLOCKED,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net X-Patchwork-Delegate: bpf@iogearbox.net After we converted the capabilities of our networking-bpf program from cap_sys_admin to cap_net_admin+cap_bpf, our networking-bpf program failed to start. Because it failed the bpf verifier, and the error log is "R3 pointer comparison prohibited". A simple reproducer as follows, SEC("cls-ingress") int ingress(struct __sk_buff *skb) { struct iphdr *iph = (void *)(long)skb->data + sizeof(struct ethhdr); if ((long)(iph + 1) > (long)skb->data_end) return TC_ACT_STOLEN; return TC_ACT_OK; } Per discussion with Yonghong and Alexei [1], comparison of two packet pointers is not a pointer leak. This patch fixes it. Our local kernel is 6.1.y and we expect this fix to be backported to 6.1.y, so stable is CCed. [1]. https://lore.kernel.org/bpf/CAADnVQ+Nmspr7Si+pxWn8zkE7hX-7s93ugwC+94aXSy4uQ9vBg@mail.gmail.com/ Suggested-by: Yonghong Song Suggested-by: Alexei Starovoitov Signed-off-by: Yafang Shao Acked-by: Eduard Zingerman Cc: stable@vger.kernel.org --- kernel/bpf/verifier.c | 17 +++++++++-------- 1 file changed, 9 insertions(+), 8 deletions(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 4ccca1f..b6b60cd 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -14047,6 +14047,12 @@ static int check_cond_jmp_op(struct bpf_verifier_env *env, return -EINVAL; } + /* check src2 operand */ + err = check_reg_arg(env, insn->dst_reg, SRC_OP); + if (err) + return err; + + dst_reg = ®s[insn->dst_reg]; if (BPF_SRC(insn->code) == BPF_X) { if (insn->imm != 0) { verbose(env, "BPF_JMP/JMP32 uses reserved fields\n"); @@ -14058,12 +14064,13 @@ static int check_cond_jmp_op(struct bpf_verifier_env *env, if (err) return err; - if (is_pointer_value(env, insn->src_reg)) { + src_reg = ®s[insn->src_reg]; + if (!(reg_is_pkt_pointer_any(dst_reg) && reg_is_pkt_pointer_any(src_reg)) && + is_pointer_value(env, insn->src_reg)) { verbose(env, "R%d pointer comparison prohibited\n", insn->src_reg); return -EACCES; } - src_reg = ®s[insn->src_reg]; } else { if (insn->src_reg != BPF_REG_0) { verbose(env, "BPF_JMP/JMP32 uses reserved fields\n"); @@ -14071,12 +14078,6 @@ static int check_cond_jmp_op(struct bpf_verifier_env *env, } } - /* check src2 operand */ - err = check_reg_arg(env, insn->dst_reg, SRC_OP); - if (err) - return err; - - dst_reg = ®s[insn->dst_reg]; is_jmp32 = BPF_CLASS(insn->code) == BPF_JMP32; if (BPF_SRC(insn->code) == BPF_K) {