netdev - [PATCH 1/5] bpf: use const pointer for struct_ops cfi

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Message-ID: <20251231173633.3981832-2-csander@purestorage.com>
Date: Wed, 31 Dec 2025 10:36:29 -0700
From: Caleb Sander Mateos <csander@...estorage.com>
To: Jiri Kosina <jikos@...nel.org>,
	Benjamin Tissoires <bentiss@...nel.org>,
	Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
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	Mahanta Jambigi <mjambigi@...ux.ibm.com>,
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	Maxime Coquelin <mcoquelin.stm32@...il.com>,
	Alexandre Torgue <alexandre.torgue@...s.st.com>
Cc: linux-input@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	bpf@...r.kernel.org,
	netdev@...r.kernel.org,
	sched-ext@...ts.linux.dev,
	linux-rdma@...r.kernel.org,
	linux-s390@...r.kernel.org,
	linux-kselftest@...r.kernel.org,
	linux-stm32@...md-mailman.stormreply.com,
	linux-arm-kernel@...ts.infradead.org,
	Caleb Sander Mateos <csander@...estorage.com>
Subject: [PATCH 1/5] bpf: use const pointer for struct_ops cfi_stubs

struct bpf_struct_ops's cfi_stubs field is used as a readonly pointer
but has type void *. Change its type to void const * to allow it to
point to readonly global memory. Change the void ** casts of cfi_stubs
to void * const * accordingly.

Signed-off-by: Caleb Sander Mateos <csander@...estorage.com>
---
 include/linux/bpf.h         | 2 +-
 kernel/bpf/bpf_struct_ops.c | 6 +++---
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 4e7d72dfbcd4..d74189ea1066 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1977,11 +1977,11 @@ struct bpf_struct_ops {
 			   void *kdata, const void *udata);
 	int (*reg)(void *kdata, struct bpf_link *link);
 	void (*unreg)(void *kdata, struct bpf_link *link);
 	int (*update)(void *kdata, void *old_kdata, struct bpf_link *link);
 	int (*validate)(void *kdata);
-	void *cfi_stubs;
+	void const *cfi_stubs;
 	struct module *owner;
 	const char *name;
 	struct btf_func_model func_models[BPF_STRUCT_OPS_MAX_NR_MEMBERS];
 };
 
diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c
index c43346cb3d76..42cfc3e0bc68 100644
--- a/kernel/bpf/bpf_struct_ops.c
+++ b/kernel/bpf/bpf_struct_ops.c
@@ -321,11 +321,11 @@ static bool is_module_member(const struct btf *btf, u32 id)
 	return !strcmp(btf_name_by_offset(btf, t->name_off), "module");
 }
 
 int bpf_struct_ops_supported(const struct bpf_struct_ops *st_ops, u32 moff)
 {
-	void *func_ptr = *(void **)(st_ops->cfi_stubs + moff);
+	void *func_ptr = *(void * const *)(st_ops->cfi_stubs + moff);
 
 	return func_ptr ? 0 : -ENOTSUPP;
 }
 
 int bpf_struct_ops_desc_init(struct bpf_struct_ops_desc *st_ops_desc,
@@ -444,11 +444,11 @@ int bpf_struct_ops_desc_init(struct bpf_struct_ops_desc *st_ops_desc,
 				mname, st_ops->name);
 			err = -EINVAL;
 			goto errout;
 		}
 
-		stub_func_addr = *(void **)(st_ops->cfi_stubs + moff);
+		stub_func_addr = *(void * const *)(st_ops->cfi_stubs + moff);
 		err = prepare_arg_info(btf, st_ops->name, mname,
 				       func_proto, stub_func_addr,
 				       arg_info + i);
 		if (err)
 			goto errout;
@@ -833,11 +833,11 @@ static long bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,
 		*pksym++ = ksym;
 
 		trampoline_start = image_off;
 		err = bpf_struct_ops_prepare_trampoline(tlinks, link,
 						&st_ops->func_models[i],
-						*(void **)(st_ops->cfi_stubs + moff),
+						*(void * const *)(st_ops->cfi_stubs + moff),
 						&image, &image_off,
 						st_map->image_pages_cnt < MAX_TRAMP_IMAGE_PAGES);
 		if (err)
 			goto reset_unlock;
 
-- 
2.45.2