On 12/12/22 7:04 PM, Hao Sun wrote:
Verify that nullness information is not porpagated in the branches
of register to register JEQ and JNE operations if one of them is
PTR_TO_BTF_ID.
Thanks for the fix and test.
Signed-off-by: Hao Sun <sunhao.th@xxxxxxxxx>
Acked-by: Yonghong Song <yhs@xxxxxx>
---
.../bpf/verifier/jeq_infer_not_null.c | 22 +++++++++++++++++++
1 file changed, 22 insertions(+)
diff --git a/tools/testing/selftests/bpf/verifier/jeq_infer_not_null.c b/tools/testing/selftests/bpf/verifier/jeq_infer_not_null.c
index 67a1c07ead34..b2b215227d97 100644
--- a/tools/testing/selftests/bpf/verifier/jeq_infer_not_null.c
+++ b/tools/testing/selftests/bpf/verifier/jeq_infer_not_null.c
@@ -172,3 +172,25 @@
.prog_type = BPF_PROG_TYPE_XDP,
.result = ACCEPT,
},
+{
+ "jne/jeq infer not null, PTR_TO_MAP_OR_NULL unchanged with PTR_TO_BTF_ID reg",
+ .insns = {
+ 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_LD_MAP_FD(BPF_REG_1, 0),
+ /* r6 = bpf_map->inner_map_meta; */
+ BPF_LDX_MEM(BPF_DW, BPF_REG_6, BPF_REG_1, 8),
This bpf_map->inner_map_meta requires CO-RE. It works now but could be fragile
in different platform and in the future bpf_map changes. Take a look at the
map_ptr_kern.c which uses "__attribute__((preserve_access_index))" at the
"struct bpf_map".
Please translate this verifer test into a proper bpf prog in C code such that it
can use the CO-RE in libbpf. It should run under test_progs instead of
test_verifier. The bpf prog can include the "vmlinux.h" to get the
"__attribute__((preserve_access_index))" for free. Take a look at
https://lore.kernel.org/all/20221207201648.2990661-2-andrii@xxxxxxxxxx/ which
has example on how to check verifier message in test_progs.
+ /* r0 = map_lookup_elem(r1, r2); */
+ BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem),
+ /* if (r0 == r6) read *r0; */
+ BPF_JMP_REG(BPF_JEQ, BPF_REG_6, BPF_REG_0, 1),
+ BPF_EXIT_INSN(),
+ BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ },
+ .fixup_map_hash_8b = { 3 },
+ .prog_type = BPF_PROG_TYPE_XDP,
+ .result = REJECT,
+ .errstr = "R0 invalid mem access 'map_value_or_null'",
+},
