selftests/bpf: Test for null-pointer-deref bugfix in resolve_prog_type()

This test verifies that resolve_prog_type() works as expected when
`attach_prog_fd` is not passed in.

`prog->aux->dst_prog` in resolve_prog_type() is assigned by
`attach_prog_fd`, and would be NULL if `attach_prog_fd` is not provided.

Loading EXT prog with bpf_dynptr_from_skb() kfunc call in this way will
lead to null-pointer-deref.

Verify that the null-pointer-deref bug in resolve_prog_type() is fixed.

Signed-off-by: Tengda Wu <wutengda@huaweicloud.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20240711145819.254178-3-wutengda@huaweicloud.com

diff --git a/tools/testing/selftests/bpf/verifier/calls.c b/tools/testing/selftests/bpf/verifier/calls.c
index d76ef20188592e32971a97b4607c101a288c462f..d0cdd156cd55582a2b47ef7fa395c7bc86bc8f78 100644 (file)
--- a/tools/testing/selftests/bpf/verifier/calls.c
+++ b/tools/testing/selftests/bpf/verifier/calls.c
@@ -275,6 +275,19 @@
        .result_unpriv = REJECT,
        .result = ACCEPT,
 },
+{
+       "calls: invalid kfunc call: must provide (attach_prog_fd, btf_id) pair when freplace",
+       .insns = {
+       BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, BPF_PSEUDO_KFUNC_CALL, 0, 0),
+       BPF_EXIT_INSN(),
+       },
+       .prog_type = BPF_PROG_TYPE_EXT,
+       .result = REJECT,
+       .errstr = "Tracing programs must provide btf_id",
+       .fixup_kfunc_btf_id = {
+               { "bpf_dynptr_from_skb", 0 },
+       },
+},
 {
        "calls: basic sanity",
        .insns = {