selftests/bpf: Add test for reg2btf_ids out of bounds access

This test tries to pass a PTR_TO_BTF_ID_OR_NULL to the release function, which would trigger a out of bounds access without the fix in commit 45ce4b4 ("bpf: Fix crash due to out of bounds access into reg2btf_ids.") but after the fix, it should only index using base_type(reg->type), which should be less than __BPF_REG_TYPE_MAX, and also not permit any type flags to be set for the reg->type. Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220220023138.2224652-1-memxor@gmail.com

Author: kkdwvd

tools/testing/selftests/bpf/verifier/calls.c

@@ -96,6 +96,25 @@
 { "bpf_kfunc_call_test_mem_len_fail1", 2 },
 },
 },
+{
+"calls: trigger reg2btf_ids[reg->type] for reg->type > __BPF_REG_TYPE_MAX",
+.insns = {
+BPF_MOV64_REG(BPF_REG_1, BPF_REG_10),
+BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -8),
+BPF_ST_MEM(BPF_DW, BPF_REG_1, 0, 0),
+BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, BPF_PSEUDO_KFUNC_CALL, 0, 0),
+BPF_MOV64_REG(BPF_REG_1, BPF_REG_0),
+BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, BPF_PSEUDO_KFUNC_CALL, 0, 0),
+BPF_EXIT_INSN(),
+},
+.prog_type = BPF_PROG_TYPE_SCHED_CLS,
+.result = REJECT,
+.errstr = "arg#0 pointer type STRUCT prog_test_ref_kfunc must point",
+.fixup_kfunc_btf_id = {
+{ "bpf_kfunc_call_test_acquire", 3 },
+{ "bpf_kfunc_call_test_release", 5 },
+},
+},
 {
 "calls: basic sanity",
 .insns = {