bpf: handle ldimm64 properly in check_cfg()

ldimm64 instructions are 16-byte long, and so have to be handled
appropriately in check_cfg(), just like the rest of BPF verifier does.

This has implications in three places:
  - when determining next instruction for non-jump instructions;
  - when determining next instruction for callback address ldimm64
    instructions (in visit_func_call_insn());
  - when checking for unreachable instructions, where second half of
    ldimm64 is expected to be unreachable;

We take this also as an opportunity to report jump into the middle of
ldimm64. And adjust few test_verifier tests accordingly.

Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Reported-by: Hao Sun <sunhao.th@gmail.com>
Fixes: 475fb78fbf48 ("bpf: verifier (add branch/goto checks)")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20231110002638.4168352-2-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 6 insertions, 2 deletions

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index b4825d3cdb29..35bff17396c0 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -909,10 +909,14 @@ bpf_ctx_record_field_size(struct bpf_insn_access_aux *aux, u32 size)
 	aux->ctx_field_size = size;
 }
 
+static bool bpf_is_ldimm64(const struct bpf_insn *insn)
+{
+	return insn->code == (BPF_LD | BPF_IMM | BPF_DW);
+}
+
 static inline bool bpf_pseudo_func(const struct bpf_insn *insn)
 {
-	return insn->code == (BPF_LD | BPF_IMM | BPF_DW) &&
-	       insn->src_reg == BPF_PSEUDO_FUNC;
+	return bpf_is_ldimm64(insn) && insn->src_reg == BPF_PSEUDO_FUNC;
 }
 
 struct bpf_prog_ops {