Merge branch 'fix-unique-field-logic-in-btf'

Kumar Kartikeya Dwivedi says:

====================
Fix unique field logic in BTF

Fix constraint of certain fields that have to be unique when nested
structs are present, BPF_REFCOUNT which should be marked as unique.
See commit logs for details. While at it, fix improper offset check.

Changelog:
----------
v1 -> v2
v1: https://lore.kernel.org/bpf/20260719142401.2420111-1-memxor@gmail.com

 * Add fix for BPF_REFCOUNT not being unique. (Sashiko)
 * Roll improper offset warning check into series. (Sashiko)
====================

Link: https://patch.msgid.link/20260719153634.2908692-1-memxor@gmail.com
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>

2 files changed, 64 insertions, 14 deletions

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index cbb1e49b9bcb..4eeeaeb69790 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -3669,7 +3669,7 @@ static int btf_get_field_type(const struct btf *btf, const struct btf_type *var_
 		{ BPF_LIST_NODE, "bpf_list_node", false },
 		{ BPF_RB_ROOT, "bpf_rb_root", false },
 		{ BPF_RB_NODE, "bpf_rb_node", false },
-		{ BPF_REFCOUNT, "bpf_refcount", false },
+		{ BPF_REFCOUNT, "bpf_refcount", true },
 	};
 	int type = 0, i;
 	const char *name = __btf_name_by_offset(btf, var_type->name_off);
@@ -3751,7 +3751,7 @@ static int btf_repeat_fields(struct btf_field_info *info, int info_cnt,
 static int btf_find_struct_field(const struct btf *btf,
 				 const struct btf_type *t, u32 field_mask,
 				 struct btf_field_info *info, int info_cnt,
-				 u32 level);
+				 u32 level, u32 *seen_mask);
 
 /* Find special fields in the struct type of a field.
  *
@@ -3762,7 +3762,7 @@ static int btf_find_struct_field(const struct btf *btf,
 static int btf_find_nested_struct(const struct btf *btf, const struct btf_type *t,
 				  u32 off, u32 nelems,
 				  u32 field_mask, struct btf_field_info *info,
-				  int info_cnt, u32 level)
+				  int info_cnt, u32 level, u32 *seen_mask)
 {
 	int ret, err, i;
 
@@ -3770,7 +3770,7 @@ static int btf_find_nested_struct(const struct btf *btf, const struct btf_type *
 	if (level >= MAX_RESOLVE_DEPTH)
 		return -E2BIG;
 
-	ret = btf_find_struct_field(btf, t, field_mask, info, info_cnt, level);
+	ret = btf_find_struct_field(btf, t, field_mask, info, info_cnt, level, seen_mask);
 
 	if (ret <= 0)
 		return ret;
@@ -3827,7 +3827,7 @@ static int btf_find_field_one(const struct btf *btf,
 		if (expected_size && expected_size != sz * nelems)
 			return 0;
 		ret = btf_find_nested_struct(btf, var_type, off, nelems, field_mask,
-					     &info[0], info_cnt, level);
+					     &info[0], info_cnt, level, seen_mask);
 		return ret;
 	}
 
@@ -3892,11 +3892,11 @@ static int btf_find_field_one(const struct btf *btf,
 static int btf_find_struct_field(const struct btf *btf,
 				 const struct btf_type *t, u32 field_mask,
 				 struct btf_field_info *info, int info_cnt,
-				 u32 level)
+				 u32 level, u32 *seen_mask)
 {
 	int ret, idx = 0;
 	const struct btf_member *member;
-	u32 i, off, seen_mask = 0;
+	u32 i, off;
 
 	for_each_member(i, t, member) {
 		const struct btf_type *member_type = btf_type_by_id(btf,
@@ -3910,7 +3910,7 @@ static int btf_find_struct_field(const struct btf *btf,
 
 		ret = btf_find_field_one(btf, t, member_type, i,
 					 off, 0,
-					 field_mask, &seen_mask,
+					 field_mask, seen_mask,
 					 &info[idx], info_cnt - idx, level);
 		if (ret < 0)
 			return ret;
@@ -3921,11 +3921,11 @@ static int btf_find_struct_field(const struct btf *btf,
 
 static int btf_find_datasec_var(const struct btf *btf, const struct btf_type *t,
 				u32 field_mask, struct btf_field_info *info,
-				int info_cnt, u32 level)
+				int info_cnt, u32 level, u32 *seen_mask)
 {
 	int ret, idx = 0;
 	const struct btf_var_secinfo *vsi;
-	u32 i, off, seen_mask = 0;
+	u32 i, off;
 
 	for_each_vsi(i, t, vsi) {
 		const struct btf_type *var = btf_type_by_id(btf, vsi->type);
@@ -3933,7 +3933,7 @@ static int btf_find_datasec_var(const struct btf *btf, const struct btf_type *t,
 
 		off = vsi->offset;
 		ret = btf_find_field_one(btf, var, var_type, -1, off, vsi->size,
-					 field_mask, &seen_mask,
+					 field_mask, seen_mask,
 					 &info[idx], info_cnt - idx,
 					 level);
 		if (ret < 0)
@@ -3947,10 +3947,12 @@ static int btf_find_field(const struct btf *btf, const struct btf_type *t,
 			  u32 field_mask, struct btf_field_info *info,
 			  int info_cnt)
 {
+	u32 seen_mask = 0;
+
 	if (__btf_type_is_struct(t))
-		return btf_find_struct_field(btf, t, field_mask, info, info_cnt, 0);
+		return btf_find_struct_field(btf, t, field_mask, info, info_cnt, 0, &seen_mask);
 	else if (btf_type_is_datasec(t))
-		return btf_find_datasec_var(btf, t, field_mask, info, info_cnt, 0);
+		return btf_find_datasec_var(btf, t, field_mask, info, info_cnt, 0, &seen_mask);
 	return -EINVAL;
 }
 
@@ -4168,7 +4170,7 @@ struct btf_record *btf_parse_fields(const struct btf *btf, const struct btf_type
 			rec->spin_lock_off = rec->fields[i].offset;
 			break;
 		case BPF_RES_SPIN_LOCK:
-			WARN_ON_ONCE(rec->spin_lock_off >= 0);
+			WARN_ON_ONCE(rec->res_spin_lock_off >= 0);
 			/* Cache offset for faster lookup at runtime */
 			rec->res_spin_lock_off = rec->fields[i].offset;
 			break;
diff --git a/tools/testing/selftests/bpf/prog_tests/btf.c b/tools/testing/selftests/bpf/prog_tests/btf.c
index 66855cbd6b73..67b9015cbd98 100644
--- a/tools/testing/selftests/bpf/prog_tests/btf.c
+++ b/tools/testing/selftests/bpf/prog_tests/btf.c
@@ -4250,6 +4250,54 @@ static struct btf_raw_test raw_tests[] = {
 	.max_entries = 1,
 },
 
+/*
+ * struct inner {
+ *     struct bpf_spin_lock lock;
+ * };
+ *
+ * struct value {
+ *     struct bpf_spin_lock lock;
+ *     struct inner nested;
+ * };
+ */
+{
+	.descr = "struct test duplicate nested unique fields",
+	.raw_types = {
+		BTF_TYPE_INT_ENC(NAME_TBD, BTF_INT_SIGNED, 0, 32, 4),	/* [1] */
+		BTF_STRUCT_ENC(NAME_TBD, 1, 4),				/* [2] */
+		BTF_MEMBER_ENC(NAME_TBD, 1, 0),
+		BTF_STRUCT_ENC(NAME_TBD, 1, 4),				/* [3] */
+		BTF_MEMBER_ENC(NAME_TBD, 2, 0),
+		BTF_STRUCT_ENC(NAME_TBD, 2, 8),				/* [4] */
+		BTF_MEMBER_ENC(NAME_TBD, 2, 0),
+		BTF_MEMBER_ENC(NAME_TBD, 3, 32),
+		BTF_END_RAW,
+	},
+	BTF_STR_SEC("\0int\0bpf_spin_lock\0val\0inner\0lock\0value\0lock\0nested"),
+	.btf_load_err = true,
+},
+
+/*
+ * struct value {
+ *     struct bpf_refcount a;
+ *     struct bpf_refcount b;
+ * };
+ */
+{
+	.descr = "struct test duplicate bpf_refcount fields",
+	.raw_types = {
+		BTF_TYPE_INT_ENC(NAME_TBD, BTF_INT_SIGNED, 0, 32, 4),	/* [1] */
+		BTF_STRUCT_ENC(NAME_TBD, 1, 4),				/* [2] */
+		BTF_MEMBER_ENC(NAME_TBD, 1, 0),
+		BTF_STRUCT_ENC(NAME_TBD, 2, 8),				/* [3] */
+		BTF_MEMBER_ENC(NAME_TBD, 2, 0),
+		BTF_MEMBER_ENC(NAME_TBD, 2, 32),
+		BTF_END_RAW,
+	},
+	BTF_STR_SEC("\0int\0bpf_refcount\0refs\0value\0a\0b"),
+	.btf_load_err = true,
+},
+
 {
 	.descr = "struct test repeated fields count overflow",
 	.raw_types = {