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
45ce4b4f9009 ("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

diff --git a/tools/testing/selftests/bpf/verifier/calls.c b/tools/testing/selftests/bpf/verifier/calls.c
index 829be2b9e08e1440729e51f02da66f20ab8755be..0a8ea60c2a80ced6a15c1aac04c9e1fa3f6da3f5 100644 (file)
--- a/tools/testing/selftests/bpf/verifier/calls.c
+++ b/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 = {