From patchwork Mon Jan 15 08:20:27 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Hao Sun X-Patchwork-Id: 13519377 X-Patchwork-Delegate: bpf@iogearbox.net Received: from mail-wm1-f42.google.com (mail-wm1-f42.google.com [209.85.128.42]) (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 BF9B0F9EC; Mon, 15 Jan 2024 08:20:35 +0000 (UTC) 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="NkbhZcyg" Received: by mail-wm1-f42.google.com with SMTP id 5b1f17b1804b1-40e779f0253so5992855e9.1; Mon, 15 Jan 2024 00:20:35 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1705306833; x=1705911633; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=dmqRToETWwbrShoMFrJKx33TAguFGIp6Y4ctqqBPrjI=; b=NkbhZcygPGgmSUftnsrGt/m5ugCC/3hCh4Ha4fgyLOjWr/lorryLFz0BdRZkpI5DIj O3QCsMpZ65CfuUoEDslNv6VCAh4Y2HPJx8kaFHMuS3j71HkK3TMLvBLCD91ROd2FDqLn AjmGH8cZp6/id0GfLTzdlUV3jr86os0jLhZ/LwM1Upg3Z/8weGBaP/92QA5fGYpMvhAa /J6UyVs8AvTzMvffBWY6ZkQGkuOs9zKJD2MPEkfcrL6qGlm8lNB9S3T3Z40p66h71wtY Rl+hV8MGL5BXlNaEpDVLX4wbW6hjDD9kSFHQKrYjZLliwZMZBhbnbo3rBQEGjMlSLocX K2lQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1705306833; x=1705911633; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=dmqRToETWwbrShoMFrJKx33TAguFGIp6Y4ctqqBPrjI=; b=M8pd5DYB55tdWe4tfGWH/pIQtZVVv1sen7h+4Tp+TeCgZXOXLF/benrYW4ryxGlljg Fguor0q14taYk2vhZ5tw0+JOqayZ5sCQrlSUN57b86cthaHjrFjKDVfyFBlDz14V1YIK xZWJ7TdsTLonLtSUeICeA/jNfCximiUx1ZKJe2sJXajruaOZPEPtmsXaMmScgiFsrqEZ YALiQYnP779K35R1lgf6k3CyB2p4UTptXgbBk6d3+iomOEl13c2pAXvkyPYt8F5b78fx E+iwje9OPIQuO8IgeCimtBcR3a3dq5pDheQxz3w8VRwIDG3VehYNl1eJfTyS7MIXrcUi cWtQ== X-Gm-Message-State: AOJu0YzYk+QMaZ4K3G4tidxKiZ6HeqBKzo61hfbx8Q5s3PHYW1n5Sgvd t51+rXYHdcIFwinhI74nOClj3e4PMg== X-Google-Smtp-Source: AGHT+IGQTbsiEJggxWBpQTtpDVbHo5BO+tu+EPDgUlEzLPZiWhQOD9r3sEeg6gS0HOWniFPeUqNtMg== X-Received: by 2002:a05:600c:524c:b0:40e:397e:16e7 with SMTP id fc12-20020a05600c524c00b0040e397e16e7mr2800231wmb.3.1705306833154; Mon, 15 Jan 2024 00:20:33 -0800 (PST) Received: from staff-net-cx-3510.intern.ethz.ch (2001-67c-10ec-5784-8000--16b.net6.ethz.ch. [2001:67c:10ec:5784:8000::16b]) by smtp.gmail.com with ESMTPSA id u17-20020a05600c19d100b0040e47dc2e8fsm14981194wmq.6.2024.01.15.00.20.32 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Mon, 15 Jan 2024 00:20:32 -0800 (PST) From: Hao Sun To: bpf@vger.kernel.org Cc: willemb@google.com, ast@kernel.org, andrii@kernel.org, daniel@iogearbox.net, eddyz87@gmail.com, yonghong.song@linux.dev, linux-kernel@vger.kernel.org, Hao Sun Subject: [PATCH v4 1/2] bpf: Reject variable offset alu on PTR_TO_FLOW_KEYS Date: Mon, 15 Jan 2024 09:20:27 +0100 Message-ID: <20240115082028.9992-1-sunhao.th@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: bpf@iogearbox.net For PTR_TO_FLOW_KEYS, check_flow_keys_access() only uses fixed off for validation. However, variable offset ptr alu is not prohibited for this ptr kind. So the variable offset is not checked. The following prog is accepted: func#0 @0 0: R1=ctx() R10=fp0 0: (bf) r6 = r1 ; R1=ctx() R6_w=ctx() 1: (79) r7 = *(u64 *)(r6 +144) ; R6_w=ctx() R7_w=flow_keys() 2: (b7) r8 = 1024 ; R8_w=1024 3: (37) r8 /= 1 ; R8_w=scalar() 4: (57) r8 &= 1024 ; R8_w=scalar(smin=smin32=0, smax=umax=smax32=umax32=1024,var_off=(0x0; 0x400)) 5: (0f) r7 += r8 mark_precise: frame0: last_idx 5 first_idx 0 subseq_idx -1 mark_precise: frame0: regs=r8 stack= before 4: (57) r8 &= 1024 mark_precise: frame0: regs=r8 stack= before 3: (37) r8 /= 1 mark_precise: frame0: regs=r8 stack= before 2: (b7) r8 = 1024 6: R7_w=flow_keys(smin=smin32=0,smax=umax=smax32=umax32=1024,var_off =(0x0; 0x400)) R8_w=scalar(smin=smin32=0,smax=umax=smax32=umax32=1024, var_off=(0x0; 0x400)) 6: (79) r0 = *(u64 *)(r7 +0) ; R0_w=scalar() 7: (95) exit This prog loads flow_keys to r7, and adds the variable offset r8 to r7, and finally causes out-of-bounds access: BUG: unable to handle page fault for address: ffffc90014c80038 ... Call Trace: bpf_dispatcher_nop_func include/linux/bpf.h:1231 [inline] __bpf_prog_run include/linux/filter.h:651 [inline] bpf_prog_run include/linux/filter.h:658 [inline] bpf_prog_run_pin_on_cpu include/linux/filter.h:675 [inline] bpf_flow_dissect+0x15f/0x350 net/core/flow_dissector.c:991 bpf_prog_test_run_flow_dissector+0x39d/0x620 net/bpf/test_run.c:1359 bpf_prog_test_run kernel/bpf/syscall.c:4107 [inline] __sys_bpf+0xf8f/0x4560 kernel/bpf/syscall.c:5475 __do_sys_bpf kernel/bpf/syscall.c:5561 [inline] __se_sys_bpf kernel/bpf/syscall.c:5559 [inline] __x64_sys_bpf+0x73/0xb0 kernel/bpf/syscall.c:5559 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0x3f/0x110 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x63/0x6b Fix this by rejecting ptr alu with variable offset on flow_keys. Applying the patch makes the program rejected with "R7 pointer arithmetic on flow_keys prohibited" Fixes: d58e468b1112 ("flow_dissector: implements flow dissector BPF hook") Signed-off-by: Hao Sun Acked-by: Yonghong Song --- Changelogs: v3 -> v4: drop the success test in the second patch. v2 -> v3: format the second patch with proper number of tabs. v1 -> v2: add two test cases for the first patch. kernel/bpf/verifier.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 9507800026cf..bd1da0d3ebce 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -12862,6 +12862,10 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env, } switch (base_type(ptr_reg->type)) { + case PTR_TO_FLOW_KEYS: + if (known) + break; + fallthrough; case CONST_PTR_TO_MAP: /* smin_val represents the known value */ if (known && smin_val == 0 && opcode == BPF_ADD) From patchwork Mon Jan 15 08:20:28 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Hao Sun X-Patchwork-Id: 13519378 X-Patchwork-Delegate: bpf@iogearbox.net Received: from mail-wm1-f53.google.com (mail-wm1-f53.google.com [209.85.128.53]) (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 446806FAE; Mon, 15 Jan 2024 08:20:39 +0000 (UTC) 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="Yxcb6PBK" Received: by mail-wm1-f53.google.com with SMTP id 5b1f17b1804b1-40e7065b7bdso14061785e9.3; Mon, 15 Jan 2024 00:20:39 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1705306837; x=1705911637; darn=vger.kernel.org; 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=xPEUBbd6YyFY5XpshsB4nRVGBOt6Lh2x1n9bnlaCTB0=; b=Yxcb6PBKNeG8ktKUZfVHXVwiiy9NViRd6c3CtIXUkZRWzU5dSRD7fZXNrM3T6/CsdD CCGcTi8p26xgRxfKSyA//NePTg1qN2Ug8zsx0C14EnnbvliDuk4fGFS3TCTDAUh4JAdB qmBxHRKnEq0fU9GgmVx6sI/aMPyEughudux9CvxJjmo3zV636aH7QVuYelRncu6oFlH2 SLje4/YoHJJXwU87tAvSqCxXbULCxXdRfiuVD/bN1XRNsp+UU94EItGqXRtQjaJn9ZEY tGP9io52loXi75nE0UWuUW6XYZI5OhK9JSo0sGnvIrK3jEmQ9fctox6wlvvxTUxAcvNY EZhw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1705306837; x=1705911637; 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=xPEUBbd6YyFY5XpshsB4nRVGBOt6Lh2x1n9bnlaCTB0=; b=VQ8nuG+KoZH50J4Zvwl0o/6RuXgrruHR+n/hyOWv952iEeFw9XRnj67fRA9C3IO4qN kgONxWt/cUO8b7zFpiWUn2evbY2KhUlrUdIV9SCUgVqEdjbLwjp0/asW3mdL1vQnALzb hrlMYSoY4dLSvn8WI5HxleEYI/35qLOkpHgtqrHcwmqhNMHxruMm3/bK+R5JRhH0JJYC myL48UEpW6gepeZrLNaO7pBKVc+2EWTiuqhCEZO9pOt2YTso07zss21c6y69l1zhF4lt viwZ+DKjHKX+pX2EBm6QBRdDCajUphUjZN32eQg0282ioDcv2wGsVBtKVMnXgslqqJ9a 2MGQ== X-Gm-Message-State: AOJu0Ywt22ZcVh76/T6mF0CtCCM7W5CgbgPrmnAw0nqvTqbGPr250bLQ BZlxQbZzCtSlbttQ3Y8oFsXP9szSkQ== X-Google-Smtp-Source: AGHT+IHtupY3BThxNfDZY5xZCItDpyEGHgdJeJnGq9MuDhEU1VfnfnmD47+LQJ4Q89BTUm6IH2UrhQ== X-Received: by 2002:a05:600c:4292:b0:40d:3b0a:6edb with SMTP id v18-20020a05600c429200b0040d3b0a6edbmr1856776wmc.183.1705306837028; Mon, 15 Jan 2024 00:20:37 -0800 (PST) Received: from staff-net-cx-3510.intern.ethz.ch (2001-67c-10ec-5784-8000--16b.net6.ethz.ch. [2001:67c:10ec:5784:8000::16b]) by smtp.gmail.com with ESMTPSA id u17-20020a05600c19d100b0040e47dc2e8fsm14981194wmq.6.2024.01.15.00.20.36 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Mon, 15 Jan 2024 00:20:36 -0800 (PST) From: Hao Sun To: bpf@vger.kernel.org Cc: willemb@google.com, ast@kernel.org, andrii@kernel.org, daniel@iogearbox.net, eddyz87@gmail.com, yonghong.song@linux.dev, linux-kernel@vger.kernel.org, Hao Sun Subject: [PATCH v4 2/2] selftests/bpf: Add test for alu on PTR_TO_FLOW_KEYS Date: Mon, 15 Jan 2024 09:20:28 +0100 Message-ID: <20240115082028.9992-2-sunhao.th@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240115082028.9992-1-sunhao.th@gmail.com> References: <20240115082028.9992-1-sunhao.th@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: bpf@iogearbox.net Add a test case for PTR_TO_FLOW_KEYS alu. Testing if alu with variable offset on flow_keys is rejected. Signed-off-by: Hao Sun Acked-by: Yonghong Song --- .../bpf/progs/verifier_value_illegal_alu.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) diff --git a/tools/testing/selftests/bpf/progs/verifier_value_illegal_alu.c b/tools/testing/selftests/bpf/progs/verifier_value_illegal_alu.c index 71814a753216..a9ab37d3b9e2 100644 --- a/tools/testing/selftests/bpf/progs/verifier_value_illegal_alu.c +++ b/tools/testing/selftests/bpf/progs/verifier_value_illegal_alu.c @@ -146,4 +146,23 @@ l0_%=: exit; \ : __clobber_all); } +SEC("flow_dissector") +__description("flow_keys illegal alu op with variable offset") +__failure __msg("R7 pointer arithmetic on flow_keys prohibited") +__naked void flow_keys_illegal_variable_offset_alu(void) +{ + asm volatile(" \ + r6 = r1; \ + r7 = *(u64*)(r6 + %[flow_keys_off]); \ + r8 = 8; \ + r8 /= 1; \ + r8 &= 8; \ + r7 += r8; \ + r0 = *(u64*)(r7 + 0); \ + exit; \ +" : + : __imm_const(flow_keys_off, offsetof(struct __sk_buff, flow_keys)) + : __clobber_all); +} + char _license[] SEC("license") = "GPL";