[PATCH bpf-next v1 12/13] selftests/bpf: Add dynptr partial slot overwrite tests

Kumar Kartikeya Dwivedi
2022-10-18T14:00:26Z

Try creating a dynptr, then overwriting second slot with first slot of
another dynptr. Then, the first slot of first dynptr should also be
invalidated, but without our fix that does not happen. As a consequence,
the unfixed case allows passing first dynptr (as the kernel check only
checks for slot_type and then first_slot == true).

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
tools/testing/selftests/bpf/verifier/dynptr.c | 58 +++++++++++++++++++
1 file changed, 58 insertions(+)

diff --git a/tools/testing/selftests/bpf/verifier/dynptr.c b/tools/testing/selftests/bpf/verifier/dynptr.c
index 1aa7241e8a9e..8c57bc9e409f 100644
--- a/tools/testing/selftests/bpf/verifier/dynptr.c
+++ b/tools/testing/selftests/bpf/verifier/dynptr.c
@@ -122,3 +122,61 @@
.result = REJECT,
.errstr = "dynptr has to be at the constant offset",
},
+{
+ "dynptr: partial dynptr slot invalidate",
+ .insns = {
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_LD_MAP_FD(BPF_REG_6, 0),
+ BPF_LD_MAP_FD(BPF_REG_7, 0),
+ BPF_MOV64_REG(BPF_REG_1, BPF_REG_7),
+ BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
+ BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),
+ BPF_ST_MEM(BPF_DW, BPF_REG_2, 0, 0),
+ BPF_MOV64_REG(BPF_REG_3, BPF_REG_2),
+ BPF_MOV64_IMM(BPF_REG_4, 0),
+ BPF_MOV64_REG(BPF_REG_8, BPF_REG_2),
+ BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_update_elem),
+ BPF_MOV64_REG(BPF_REG_1, BPF_REG_7),
+ BPF_MOV64_REG(BPF_REG_2, BPF_REG_8),
+ 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_7, BPF_REG_0),
+ BPF_MOV64_REG(BPF_REG_1, BPF_REG_6),
+ BPF_MOV64_IMM(BPF_REG_2, 8),
+ BPF_MOV64_IMM(BPF_REG_3, 0),
+ BPF_MOV64_REG(BPF_REG_4, BPF_REG_10),
+ BPF_ALU64_IMM(BPF_ADD, BPF_REG_4, -24),
+ BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_ringbuf_reserve_dynptr),
+ BPF_ST_MEM(BPF_DW, BPF_REG_10, -16, 0),
+ BPF_MOV64_REG(BPF_REG_1, BPF_REG_7),
+ BPF_MOV64_IMM(BPF_REG_2, 8),
+ BPF_MOV64_IMM(BPF_REG_3, 0),
+ BPF_MOV64_REG(BPF_REG_4, BPF_REG_10),
+ BPF_ALU64_IMM(BPF_ADD, BPF_REG_4, -16),
+ BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_dynptr_from_mem),
+ BPF_MOV64_REG(BPF_REG_1, BPF_REG_10),
+ BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -512),
+ BPF_MOV64_IMM(BPF_REG_2, 488),
+ BPF_MOV64_REG(BPF_REG_3, BPF_REG_10),
+ BPF_ALU64_IMM(BPF_ADD, BPF_REG_3, -24),
+ BPF_MOV64_IMM(BPF_REG_4, 0),
+ BPF_MOV64_IMM(BPF_REG_5, 0),
+ BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_dynptr_read),
+ BPF_MOV64_IMM(BPF_REG_8, 1),
+ BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 1),
+ BPF_MOV64_IMM(BPF_REG_8, 0),
+ BPF_MOV64_REG(BPF_REG_1, BPF_REG_10),
+ BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -24),
+ BPF_MOV64_IMM(BPF_REG_2, 0),
+ BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_ringbuf_discard_dynptr),
+ BPF_MOV64_REG(BPF_REG_0, BPF_REG_8),
+ BPF_EXIT_INSN(),
+ },
+ .fixup_map_ringbuf = { 1 },
+ .fixup_map_hash_8b = { 3 },
+ .result_unpriv = REJECT,
+ .errstr_unpriv = "unknown func bpf_ringbuf_reserve_dynptr#198",
+ .result = REJECT,
+ .errstr = "Expected an initialized dynptr as arg #3",
+},
--
2.38.0