bpf: check changes_pkt_data property for extension programs

When processing calls to global sub-programs, verifier decides whether
to invalidate all packet pointers in current state depending on the
changes_pkt_data property of the global sub-program.

Because of this, an extension program replacing a global sub-program
must be compatible with changes_pkt_data property of the sub-program
being replaced.

This commit:
- adds changes_pkt_data flag to struct bpf_prog_aux:
  - this flag is set in check_cfg() for main sub-program;
  - in jit_subprogs() for other sub-programs;
- modifies bpf_check_attach_btf_id() to check changes_pkt_data flag;
- moves call to check_attach_btf_id() after the call to check_cfg(),
  because it needs changes_pkt_data flag to be set:

    bpf_check:
      ...                             ...
    - check_attach_btf_id             resolve_pseudo_ldimm64
      resolve_pseudo_ldimm64   -->    bpf_prog_is_offloaded
      bpf_prog_is_offloaded           check_cfg
      check_cfg                     + check_attach_btf_id
      ...                             ...

The following fields are set by check_attach_btf_id():
- env->ops
- prog->aux->attach_btf_trace
- prog->aux->attach_func_name
- prog->aux->attach_func_proto
- prog->aux->dst_trampoline
- prog->aux->mod
- prog->aux->saved_dst_attach_type
- prog->aux->saved_dst_prog_type
- prog->expected_attach_type

Neither of these fields are used by resolve_pseudo_ldimm64() or
bpf_prog_offload_verifier_prep() (for netronome and netdevsim
drivers), so the reordering is safe.

Suggested-by: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20241210041100.1898468-6-eddyz87@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index eaee2a819f4c..fe392d074973 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1527,6 +1527,7 @@ struct bpf_prog_aux {
 	bool is_extended; /* true if extended by freplace program */
 	bool jits_use_priv_stack;
 	bool priv_stack_requested;
+	bool changes_pkt_data;
 	u64 prog_array_member_cnt; /* counts how many times as member of prog_array */
 	struct mutex ext_mutex; /* mutex for is_extended and prog_array_member_cnt */
 	struct bpf_arena *arena;