From patchwork Wed Jan 10 12:53:16 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Hao Sun X-Patchwork-Id: 13516107 X-Patchwork-Delegate: bpf@iogearbox.net Received: from mail-wr1-f48.google.com (mail-wr1-f48.google.com [209.85.221.48]) (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 15B0547A55; Wed, 10 Jan 2024 12:53:33 +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="QRCt8dBu" Received: by mail-wr1-f48.google.com with SMTP id ffacd0b85a97d-3376f71fcbbso2434324f8f.1; Wed, 10 Jan 2024 04:53:33 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1704891212; x=1705496012; 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=Uoyz0fX05VFZUA0YqL9VDmTIjZubn+1o1Tubn/qOGIQ=; b=QRCt8dBuUo61U80x+UbI9iYm4wNqiKpKo/ZCFSlWEKoYZ3vVakTuJsl4TI238dfTLV Jl+VNIWdAdgYJP1D2srrJPsZ0B0jTB2rePpPzmjX2d856iopsGt0xe+LHlw0T7RCJTWs MLELwvE/mYGu4g9qtrwlBvuOsbjJ1/K0ThBbkZdNcSc6BGf1sXdKT5KAeUWD4Y+EGH0/ PWzQMPzVpaZOew6qsW5V3nn/hcPlFSN/4L+sSefSXFn6u22MdKIw62BwWKqRBhYDrvBs ohAt/f71gVGRQP7+LYdLMUc8LZZUH9lIh0CZs7lC/3QcuVQEuU+Rl4BiVxlMDVC/3O/z 8PYA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1704891212; x=1705496012; 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=Uoyz0fX05VFZUA0YqL9VDmTIjZubn+1o1Tubn/qOGIQ=; b=cywA7dD0ucZkBZywTH9QVp7quEVksLWdHjNJaTP7G1slr1IVzMUpD8kocS7U3cTTmg zxEWwHdFfb/OiHgvv79ECE1uXZnpkbekBuGCaKGYzNDRa5KXnWU62x09gFmt1UIpphZU /A0ODZDsYuFtu5aa/GfEQ+Wu6KOBtP2HmtQAAgSOg2qRMtHMiurfqWCcGfbZqGUgzmTS FvNCcgrbxm3ihlWxei62b325bodlVOh93/tBjEuDqa8a61fA4aN/VyVFbIShTk0JXbs/ E5NWO7o5mvpaAivcdmbc5oom5kImDik5fTG9qjU+l0AVGdU2D4xJaDxkPeZVd8NkgwTE 5Rfw== X-Gm-Message-State: AOJu0YzoDx+Mib1jEI1CnPROOj9O+D7Dj0VmhtpmHnUQd/xvdtzJS1Wq +zZnyf8uVMQpWFDzqTDBiKPT1MGRmg== X-Google-Smtp-Source: AGHT+IGIAb7J0lg1izF1tG7pKhpkLK3OW1M2akqGAPGYCtE+kNQFKuA/o+fJ7slq0pY6valFev7ekw== X-Received: by 2002:a5d:5449:0:b0:336:905a:bf87 with SMTP id w9-20020a5d5449000000b00336905abf87mr357212wrv.69.1704891211635; Wed, 10 Jan 2024 04:53:31 -0800 (PST) Received: from localhost.localdomain (46-253-188-135.dynamic.monzoon.net. [46.253.188.135]) by smtp.gmail.com with ESMTPSA id k10-20020a5d524a000000b00336898daceasm4833238wrc.96.2024.01.10.04.53.30 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Wed, 10 Jan 2024 04:53:31 -0800 (PST) From: Hao Sun To: bpf@vger.kernel.org Cc: ppenkov@google.com, willemb@google.com, ast@kernel.org, linux-kernel@vger.kernel.org, Hao Sun Subject: [PATCH v2 1/2] bpf: Reject variable offset alu on PTR_TO_FLOW_KEYS Date: Wed, 10 Jan 2024 13:53:16 +0100 Message-ID: <20240110125317.13742-1-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 --- kernel/bpf/verifier.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index adbf330d364b..65f598694d55 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -12826,6 +12826,10 @@ 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 Wed Jan 10 12:53:17 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Hao Sun X-Patchwork-Id: 13516108 X-Patchwork-Delegate: bpf@iogearbox.net Received: from mail-wr1-f41.google.com (mail-wr1-f41.google.com [209.85.221.41]) (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 137DC4879C; Wed, 10 Jan 2024 12:53:44 +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="cRL6Ncmq" Received: by mail-wr1-f41.google.com with SMTP id ffacd0b85a97d-3367601a301so3783827f8f.2; Wed, 10 Jan 2024 04:53:44 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1704891223; x=1705496023; 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=CqABKYiwKfM7K5loAH80ReCJ84H8NZ8M9wGBWfUZRzg=; b=cRL6NcmqpLBo1TI++VA0idxwRZTzYO4j+NGmUEy/wEiM50wmSHeMZACmRGq8ohI6jl F+f0jXIDFj8SB+ZBU2HdQHWVyyS7BLcR/3kU2c8JZd50n6KwaII96f3+TfbtX7JwN2HT sL+70i0e2delGzgA+Nm1JJGNFAJbmjzy78pWfIg4YsFWyapbPVH1GdCzAmtgl8+KPPEg NH2IAbSPND6KDkNYjbuuCuxeZy6Ynxn72iqheBnuTZao+NmyPau4bgH/1IBDLTTpj2hK p3le1iZvmw6yWQYR9IvAtNwptkFEoxty3PSKc70vTQF7ivVhok1Eh3PDjQAd8prNb6Tj kgdw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1704891223; x=1705496023; 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=CqABKYiwKfM7K5loAH80ReCJ84H8NZ8M9wGBWfUZRzg=; b=ODcDz6l90DT9sUIWM+CWIfv5s60oqrU1sS0DSKg8q35bNYci5n9JnwfmS5JiPWOMjZ YX4Wga9Wo0TJZkZft3N8sdv6jRoxfDB24oVb5Qz1+ecqBMESj8kaP1VOCcckiAeRem6Z ekL9ZNioo05MlPSiUe1B0O4jUr8uYUxrO68IpnTSVERdfZ8u/3u5z362wUJeMe/knVyu FibDBCe9H4u7yx4cIS6g0KnnDSGYgoVGZGqMkGJYunEIPcBN3r3f0kJ1dj7Xpe5Oz4x0 LqriRSin1llLZ58VvPL6pjGGl5qSHf4pvjAitBZox/K1eGMmt4Z7Ozjm3Z4YXFAd1rD+ Xq+Q== X-Gm-Message-State: AOJu0YxqKswQ0PTsPB3HhsAhr7vzNk51zLzLes9WtSnlp08QfglSup/r u9I4D3bK+Llc+XNASlSa+6attHLaeA== X-Google-Smtp-Source: AGHT+IHZ/cnVzir4rkEaeBH6BGccxR53Y+on+jYdJPd05gA69rsuGWRAVTUjLKRumKnYpWwT3nGpOw== X-Received: by 2002:a05:600c:46c7:b0:40e:52d7:a951 with SMTP id q7-20020a05600c46c700b0040e52d7a951mr370143wmo.244.1704891222627; Wed, 10 Jan 2024 04:53:42 -0800 (PST) Received: from localhost.localdomain (46-253-188-135.dynamic.monzoon.net. [46.253.188.135]) by smtp.gmail.com with ESMTPSA id k10-20020a5d524a000000b00336898daceasm4833238wrc.96.2024.01.10.04.53.41 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Wed, 10 Jan 2024 04:53:42 -0800 (PST) From: Hao Sun To: bpf@vger.kernel.org Cc: ppenkov@google.com, willemb@google.com, ast@kernel.org, linux-kernel@vger.kernel.org, Hao Sun Subject: [PATCH v2 2/2] selftests/bpf: Add tests for alu on PTR_TO_FLOW_KEYS Date: Wed, 10 Jan 2024 13:53:17 +0100 Message-ID: <20240110125317.13742-2-sunhao.th@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240110125317.13742-1-sunhao.th@gmail.com> References: <20240110125317.13742-1-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 two cases for PTR_TO_FLOW_KEYS alu. One for rejecting alu with variable offset, another for fixed offset. Signed-off-by: Hao Sun --- .../bpf/progs/verifier_value_illegal_alu.c | 37 +++++++++++++++++++ 1 file changed, 37 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..49089361c98a 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 +146,41 @@ 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); +} + +SEC("flow_dissector") +__description("flow_keys valid alu op with fixed offset") +__success +__naked void flow_keys_legal_fixed_offset_alu(void) +{ + asm volatile(" \ + r6 = r1; \ + r7 = *(u64*)(r6 + %[flow_keys_off]); \ + 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";