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[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: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1787708035583835139 X-GMAIL-MSGID: 1787708035583835139 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: 186861 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a05:7300:2411:b0:101:2151:f287 with SMTP id m17csp769140dyi; Wed, 10 Jan 2024 04:55:29 -0800 (PST) X-Google-Smtp-Source: AGHT+IGMaiVmPhv00WQxEVjEFhPP3lGHSo+uQ7zT7rRUUaipuZYCsZhRkkhZPFqZRz9O1tYVmmN9 X-Received: by 2002:a17:902:c40f:b0:1d5:738d:8814 with SMTP id k15-20020a170902c40f00b001d5738d8814mr813023plk.96.1704891329107; Wed, 10 Jan 2024 04:55:29 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1704891329; cv=none; d=google.com; s=arc-20160816; b=lw/rHGrpG3RMSIIm5iCqk/pXxVr+DogIk+UefretBh3n2OKUdX88x9QVVCz91aBz4N 1qmIWeBv60TlVKgNVpcbnRdiY0LErgNHkJqNjkzh8K2cWWu1doLEt5ZoR8V1HtscSt7Q YzEtZ/fUItTm58d2H66UBIJG4g5lXNIyByTDLqmY8ufzo+WbAaVHcncQsKSKLKtjL1uw ddZN8l+C/GuzG3kz+dxZY7dIjNNevFmc+EpF8uakA/pEdzXir4yb74DBzAZZrvkjwfIl 4X0LxRHWLJh4OUdH/FlLoXKkeSf1Jo9Tpdn6bvC1xGs6KDOhxgEeN5DkxK+WeShs+dKq yIwg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=content-transfer-encoding:mime-version:list-unsubscribe :list-subscribe:list-id:precedence:references:in-reply-to:message-id :date:subject:cc:to:from:dkim-signature; bh=CqABKYiwKfM7K5loAH80ReCJ84H8NZ8M9wGBWfUZRzg=; fh=eFM4fk5WkBs8LhrDsavNRVRWdJWcU4uYIa0kB39/ar4=; b=WSrzT1KjGxGiSkUlTC2/HubSEoRVKOc9x3yGJAkmwUaLlv2O6OWzZ6ucsNqT0hpIWU N9GllJBGdciiUxYviWoBvKJQlD72H6Adx/slppD6jv2VKMnzHPF7nFJfZ/Q0xZRDXLcc H6lJXk7FtSGW4HcKZsv88iICFBL3lBAhQxY78Ha26eVdbDUwgk1K1gtDwAuhn5sxCBEM WuYgTG9jhofHlRNWmlyRG4mWoEfPZEl4EeMdsRatU1oEzwXLGXXsIWSntGNcsKzdEhig 3wAXhLlNUU16S/bprG+B7v6cCCeXImIEj2lxO6AkXkFmAGm0AmXycmHvlvjREAfgtsmU dWNA== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@gmail.com header.s=20230601 header.b=cRL6Ncmq; spf=pass (google.com: domain of linux-kernel+bounces-22194-ouuuleilei=gmail.com@vger.kernel.org designates 2604:1380:40f1:3f00::1 as permitted sender) smtp.mailfrom="linux-kernel+bounces-22194-ouuuleilei=gmail.com@vger.kernel.org"; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com Received: from sy.mirrors.kernel.org (sy.mirrors.kernel.org. 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[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: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1787708130682158809 X-GMAIL-MSGID: 1787708130682158809 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";