Merge branch 'fix-global-subprog-ptr_to_ctx-arg-handling'

Andrii Nakryiko says:

====================
Fix global subprog PTR_TO_CTX arg handling

Fix confusing and incorrect inference of PTR_TO_CTX argument type in BPF
global subprogs. For some program types (iters, tracepoint, any program type
that doesn't have fixed named "canonical" context type) when user uses (in
a correct and valid way) a pointer argument to user-defined anonymous struct
type, verifier will incorrectly assume that it has to be PTR_TO_CTX argument.
While it should be just a PTR_TO_MEM argument with allowed size calculated
from user-provided (even if anonymous) struct.

This did come up in practice and was very confusing to users, so let's prevent
this going forward. We had to do a slight refactoring of
btf_get_prog_ctx_type() to make it easy to support a special s390x KPROBE use
cases. See details in respective patches.

v1->v2:
  - special-case typedef bpf_user_pt_regs_t handling for KPROBE programs,
    fixing s390x after changes in patch #2.
====================

Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Alexei Starovoitov <[email protected]>

1 files changed, 8 insertions, 9 deletions

diff --git a/include/linux/btf.h b/include/linux/btf.h
index cb96f6263638..f9e56fd12a9f 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -531,10 +531,9 @@ s32 btf_find_dtor_kfunc(struct btf *btf, u32 btf_id);
 int register_btf_id_dtor_kfuncs(const struct btf_id_dtor_kfunc *dtors, u32 add_cnt,
 				struct module *owner);
 struct btf_struct_meta *btf_find_struct_meta(const struct btf *btf, u32 btf_id);
-const struct btf_type *
-btf_get_prog_ctx_type(struct bpf_verifier_log *log, const struct btf *btf,
-		      const struct btf_type *t, enum bpf_prog_type prog_type,
-		      int arg);
+bool btf_is_prog_ctx_type(struct bpf_verifier_log *log, const struct btf *btf,
+			   const struct btf_type *t, enum bpf_prog_type prog_type,
+			   int arg);
 int get_kern_ctx_btf_id(struct bpf_verifier_log *log, enum bpf_prog_type prog_type);
 bool btf_types_are_same(const struct btf *btf1, u32 id1,
 			const struct btf *btf2, u32 id2);
@@ -574,12 +573,12 @@ static inline struct btf_struct_meta *btf_find_struct_meta(const struct btf *btf
 {
 	return NULL;
 }
-static inline const struct btf_member *
-btf_get_prog_ctx_type(struct bpf_verifier_log *log, const struct btf *btf,
-		      const struct btf_type *t, enum bpf_prog_type prog_type,
-		      int arg)
+static inline bool
+btf_is_prog_ctx_type(struct bpf_verifier_log *log, const struct btf *btf,
+		     const struct btf_type *t, enum bpf_prog_type prog_type,
+		     int arg)
 {
-	return NULL;
+	return false;
 }
 static inline int get_kern_ctx_btf_id(struct bpf_verifier_log *log,
 				      enum bpf_prog_type prog_type) {