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| author | Jean-Philippe Brucker <jean-philippe@linaro.org> | 2020-12-08 19:01:52 +0100 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2020-12-10 13:11:30 -0800 |
| commit | 511a76bcb0ce242a19153658b25437906cc6070e (patch) | |
| tree | 68a8f3490dea0d331566cf6db307ca05d8b0b41a | |
| parent | b02709587ea3d699a608568ee8157d8db4fd8cae (diff) | |
| download | linux-511a76bcb0ce242a19153658b25437906cc6070e.tar.gz | |
selftests/bpf: Add test for signed 32-bit bound check bug
After a 32-bit load followed by a branch, the verifier would reduce the maximum bound of the register to 0x7fffffff, allowing a user to bypass bound checks. Ensure such a program is rejected. In the second test, the 64-bit compare should not sufficient to determine whether the signed 32-bit lower bound is 0, so the verifier should reject the second branch. Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org> Acked-by: John Fastabend <john.fastabend@gmail.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
| -rw-r--r-- | tools/testing/selftests/bpf/verifier/bounds.c | 41 |
1 files changed, 41 insertions, 0 deletions
diff --git a/tools/testing/selftests/bpf/verifier/bounds.c b/tools/testing/selftests/bpf/verifier/bounds.c index dac40de3f868..57ed67b86074 100644 --- a/tools/testing/selftests/bpf/verifier/bounds.c +++ b/tools/testing/selftests/bpf/verifier/bounds.c @@ -703,3 +703,44 @@ .fixup_map_hash_8b = { 3 }, .result = ACCEPT, }, +{ + "bounds checks after 32-bit truncation. test 1", + .insns = { + 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_JEQ, BPF_REG_0, 0, 4), + BPF_LDX_MEM(BPF_W, BPF_REG_1, BPF_REG_0, 0), + /* This used to reduce the max bound to 0x7fffffff */ + BPF_JMP_IMM(BPF_JEQ, BPF_REG_1, 0, 1), + BPF_JMP_IMM(BPF_JGT, BPF_REG_1, 0x7fffffff, 1), + BPF_MOV64_IMM(BPF_REG_0, 0), + BPF_EXIT_INSN(), + }, + .fixup_map_hash_8b = { 3 }, + .errstr_unpriv = "R0 leaks addr", + .result_unpriv = REJECT, + .result = ACCEPT, +}, +{ + "bounds checks after 32-bit truncation. test 2", + .insns = { + 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_JEQ, BPF_REG_0, 0, 4), + BPF_LDX_MEM(BPF_W, BPF_REG_1, BPF_REG_0, 0), + BPF_JMP_IMM(BPF_JSLT, BPF_REG_1, 1, 1), + BPF_JMP32_IMM(BPF_JSLT, BPF_REG_1, 0, 1), + BPF_MOV64_IMM(BPF_REG_0, 0), + BPF_EXIT_INSN(), + }, + .fixup_map_hash_8b = { 3 }, + .errstr_unpriv = "R0 leaks addr", + .result_unpriv = REJECT, + .result = ACCEPT, +}, |