linux-kernel - [PATCH 5.10 10/99] bpf, selftests: Add test case trying to taint map value pointer

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Message-Id: <20211220143029.698365332@linuxfoundation.org>
Date:   Mon, 20 Dec 2021 15:33:43 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Daniel Borkmann <daniel@...earbox.net>,
        John Fastabend <john.fastabend@...il.com>,
        Alexei Starovoitov <ast@...nel.org>
Subject: [PATCH 5.10 10/99] bpf, selftests: Add test case trying to taint map value pointer

From: Daniel Borkmann <daniel@...earbox.net>

commit b1a7288dedc6caf9023f2676b4f5ed34cf0d4029 upstream.

Add a test case which tries to taint map value pointer arithmetic into a
unknown scalar with subsequent export through the map.

Before fix:

  # ./test_verifier 1186
  #1186/u map access: trying to leak tained dst reg FAIL
  Unexpected success to load!
  verification time 24 usec
  stack depth 8
  processed 15 insns (limit 1000000) max_states_per_insn 0 total_states 1 peak_states 1 mark_read 1
  #1186/p map access: trying to leak tained dst reg FAIL
  Unexpected success to load!
  verification time 8 usec
  stack depth 8
  processed 15 insns (limit 1000000) max_states_per_insn 0 total_states 1 peak_states 1 mark_read 1
  Summary: 0 PASSED, 0 SKIPPED, 2 FAILED

After fix:

  # ./test_verifier 1186
  #1186/u map access: trying to leak tained dst reg OK
  #1186/p map access: trying to leak tained dst reg OK
  Summary: 2 PASSED, 0 SKIPPED, 0 FAILED

Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
Reviewed-by: John Fastabend <john.fastabend@...il.com>
Acked-by: Alexei Starovoitov <ast@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 tools/testing/selftests/bpf/verifier/value_ptr_arith.c |   23 +++++++++++++++++
 1 file changed, 23 insertions(+)

--- a/tools/testing/selftests/bpf/verifier/value_ptr_arith.c
+++ b/tools/testing/selftests/bpf/verifier/value_ptr_arith.c
@@ -849,6 +849,29 @@
 	.errstr_unpriv = "R0 pointer -= pointer prohibited",
 },
 {
+	"map access: trying to leak tained dst reg",
+	.insns = {
+	BPF_MOV64_IMM(BPF_REG_0, 0),
+	BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0),
+	BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
+	BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),
+	BPF_LD_MAP_FD(BPF_REG_1, 0),
+	BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
+	BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 1),
+	BPF_EXIT_INSN(),
+	BPF_MOV64_REG(BPF_REG_2, BPF_REG_0),
+	BPF_MOV32_IMM(BPF_REG_1, 0xFFFFFFFF),
+	BPF_MOV32_REG(BPF_REG_1, BPF_REG_1),
+	BPF_ALU64_REG(BPF_SUB, BPF_REG_2, BPF_REG_1),
+	BPF_STX_MEM(BPF_DW, BPF_REG_0, BPF_REG_2, 0),
+	BPF_MOV64_IMM(BPF_REG_0, 0),
+	BPF_EXIT_INSN(),
+	},
+	.fixup_map_array_48b = { 4 },
+	.result = REJECT,
+	.errstr = "math between map_value pointer and 4294967295 is not allowed",
+},
+{
 	"32bit pkt_ptr -= scalar",
 	.insns = {
 	BPF_LDX_MEM(BPF_W, BPF_REG_8, BPF_REG_1,