bpf: Mark existing lock-safe kfuncs with KF_SPINLOCK_SAFE

The verifier currently keeps a hard-coded list of kfuncs that may be
called while holding a bpf_spin_lock. With KF_SPINLOCK_SAFE available,
retaining this list creates two sources of truth and requires verifier
changes whenever another lock-safe kfunc is added.

Mark every kfunc currently accepted by kfunc_spin_allowed() with
KF_SPINLOCK_SAFE. This covers the graph, numeric iterator, resource
spin lock, arena, and stream kfuncs.

Remove the obsolete category checks and make kfunc_spin_allowed() rely
solely on the kfunc registration metadata. This preserves the behavior
of existing kfuncs while using the same mechanism for built-in and
module kfuncs.

Signed-off-by: Kaitao Cheng <chengkaitao@kylinos.cn>
Acked-by: Leon Hwang <leon.hwang@linux.dev>
Link: https://lore.kernel.org/bpf/20260805153340.34776-3-kaitao.cheng@linux.dev
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>

4 files changed, 36 insertions, 66 deletions

diff --git a/kernel/bpf/arena.c b/kernel/bpf/arena.c
index 555ee2531ef9..7b6847200b43 100644
--- a/kernel/bpf/arena.c
+++ b/kernel/bpf/arena.c
@@ -1118,9 +1118,9 @@ __bpf_kfunc int bpf_arena_reserve_pages(void *p__map, void *ptr__ign, u32 page_c
 __bpf_kfunc_end_defs();
 
 BTF_KFUNCS_START(arena_kfuncs)
-BTF_ID_FLAGS(func, bpf_arena_alloc_pages, KF_ARENA_RET | KF_ARENA_ARG2)
-BTF_ID_FLAGS(func, bpf_arena_free_pages, KF_ARENA_ARG2)
-BTF_ID_FLAGS(func, bpf_arena_reserve_pages, KF_ARENA_ARG2)
+BTF_ID_FLAGS(func, bpf_arena_alloc_pages, KF_ARENA_RET | KF_ARENA_ARG2 | KF_SPINLOCK_SAFE)
+BTF_ID_FLAGS(func, bpf_arena_free_pages, KF_ARENA_ARG2 | KF_SPINLOCK_SAFE)
+BTF_ID_FLAGS(func, bpf_arena_reserve_pages, KF_ARENA_ARG2 | KF_SPINLOCK_SAFE)
 BTF_KFUNCS_END(arena_kfuncs)
 
 static const struct btf_kfunc_id_set common_kfunc_set = {
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 4709a5ad0474..6388b6b23e49 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -4812,30 +4812,32 @@ BTF_ID_FLAGS(func, bpf_obj_drop, KF_RELEASE | KF_IMPLICIT_ARGS)
 BTF_ID_FLAGS(func, bpf_obj_drop_impl, KF_RELEASE)
 BTF_ID_FLAGS(func, bpf_percpu_obj_drop, KF_RELEASE | KF_IMPLICIT_ARGS)
 BTF_ID_FLAGS(func, bpf_percpu_obj_drop_impl, KF_RELEASE)
-BTF_ID_FLAGS(func, bpf_refcount_acquire, KF_ACQUIRE | KF_RET_NULL | KF_RCU | KF_IMPLICIT_ARGS)
-BTF_ID_FLAGS(func, bpf_refcount_acquire_impl, KF_ACQUIRE | KF_RET_NULL | KF_RCU)
-BTF_ID_FLAGS(func, bpf_list_push_front, KF_IMPLICIT_ARGS)
-BTF_ID_FLAGS(func, bpf_list_push_front_impl)
-BTF_ID_FLAGS(func, bpf_list_push_back, KF_IMPLICIT_ARGS)
-BTF_ID_FLAGS(func, bpf_list_push_back_impl)
-BTF_ID_FLAGS(func, bpf_list_add, KF_IMPLICIT_ARGS)
-BTF_ID_FLAGS(func, bpf_list_pop_front, KF_ACQUIRE | KF_RET_NULL)
-BTF_ID_FLAGS(func, bpf_list_pop_back, KF_ACQUIRE | KF_RET_NULL)
-BTF_ID_FLAGS(func, bpf_list_del, KF_ACQUIRE | KF_RET_NULL)
-BTF_ID_FLAGS(func, bpf_list_front, KF_RET_NULL)
-BTF_ID_FLAGS(func, bpf_list_back, KF_RET_NULL)
-BTF_ID_FLAGS(func, bpf_list_is_first)
-BTF_ID_FLAGS(func, bpf_list_is_last)
-BTF_ID_FLAGS(func, bpf_list_empty)
+BTF_ID_FLAGS(func, bpf_refcount_acquire,
+	     KF_ACQUIRE | KF_RET_NULL | KF_RCU | KF_IMPLICIT_ARGS | KF_SPINLOCK_SAFE)
+BTF_ID_FLAGS(func, bpf_refcount_acquire_impl,
+	     KF_ACQUIRE | KF_RET_NULL | KF_RCU | KF_SPINLOCK_SAFE)
+BTF_ID_FLAGS(func, bpf_list_push_front, KF_IMPLICIT_ARGS | KF_SPINLOCK_SAFE)
+BTF_ID_FLAGS(func, bpf_list_push_front_impl, KF_SPINLOCK_SAFE)
+BTF_ID_FLAGS(func, bpf_list_push_back, KF_IMPLICIT_ARGS | KF_SPINLOCK_SAFE)
+BTF_ID_FLAGS(func, bpf_list_push_back_impl, KF_SPINLOCK_SAFE)
+BTF_ID_FLAGS(func, bpf_list_add, KF_IMPLICIT_ARGS | KF_SPINLOCK_SAFE)
+BTF_ID_FLAGS(func, bpf_list_pop_front, KF_ACQUIRE | KF_RET_NULL | KF_SPINLOCK_SAFE)
+BTF_ID_FLAGS(func, bpf_list_pop_back, KF_ACQUIRE | KF_RET_NULL | KF_SPINLOCK_SAFE)
+BTF_ID_FLAGS(func, bpf_list_del, KF_ACQUIRE | KF_RET_NULL | KF_SPINLOCK_SAFE)
+BTF_ID_FLAGS(func, bpf_list_front, KF_RET_NULL | KF_SPINLOCK_SAFE)
+BTF_ID_FLAGS(func, bpf_list_back, KF_RET_NULL | KF_SPINLOCK_SAFE)
+BTF_ID_FLAGS(func, bpf_list_is_first, KF_SPINLOCK_SAFE)
+BTF_ID_FLAGS(func, bpf_list_is_last, KF_SPINLOCK_SAFE)
+BTF_ID_FLAGS(func, bpf_list_empty, KF_SPINLOCK_SAFE)
 BTF_ID_FLAGS(func, bpf_task_acquire, KF_ACQUIRE | KF_RCU | KF_RET_NULL)
 BTF_ID_FLAGS(func, bpf_task_release, KF_RELEASE)
-BTF_ID_FLAGS(func, bpf_rbtree_remove, KF_ACQUIRE | KF_RET_NULL)
-BTF_ID_FLAGS(func, bpf_rbtree_add, KF_IMPLICIT_ARGS)
-BTF_ID_FLAGS(func, bpf_rbtree_add_impl)
-BTF_ID_FLAGS(func, bpf_rbtree_first, KF_RET_NULL)
-BTF_ID_FLAGS(func, bpf_rbtree_root, KF_RET_NULL)
-BTF_ID_FLAGS(func, bpf_rbtree_left, KF_RET_NULL)
-BTF_ID_FLAGS(func, bpf_rbtree_right, KF_RET_NULL)
+BTF_ID_FLAGS(func, bpf_rbtree_remove, KF_ACQUIRE | KF_RET_NULL | KF_SPINLOCK_SAFE)
+BTF_ID_FLAGS(func, bpf_rbtree_add, KF_IMPLICIT_ARGS | KF_SPINLOCK_SAFE)
+BTF_ID_FLAGS(func, bpf_rbtree_add_impl, KF_SPINLOCK_SAFE)
+BTF_ID_FLAGS(func, bpf_rbtree_first, KF_RET_NULL | KF_SPINLOCK_SAFE)
+BTF_ID_FLAGS(func, bpf_rbtree_root, KF_RET_NULL | KF_SPINLOCK_SAFE)
+BTF_ID_FLAGS(func, bpf_rbtree_left, KF_RET_NULL | KF_SPINLOCK_SAFE)
+BTF_ID_FLAGS(func, bpf_rbtree_right, KF_RET_NULL | KF_SPINLOCK_SAFE)
 
 #ifdef CONFIG_CGROUPS
 BTF_ID_FLAGS(func, bpf_cgroup_acquire, KF_ACQUIRE | KF_RCU | KF_RET_NULL)
@@ -4885,9 +4887,9 @@ BTF_ID_FLAGS(func, bpf_rcu_read_lock)
 BTF_ID_FLAGS(func, bpf_rcu_read_unlock)
 BTF_ID_FLAGS(func, bpf_dynptr_slice, KF_RET_NULL)
 BTF_ID_FLAGS(func, bpf_dynptr_slice_rdwr, KF_RET_NULL)
-BTF_ID_FLAGS(func, bpf_iter_num_new, KF_ITER_NEW)
-BTF_ID_FLAGS(func, bpf_iter_num_next, KF_ITER_NEXT | KF_RET_NULL)
-BTF_ID_FLAGS(func, bpf_iter_num_destroy, KF_ITER_DESTROY)
+BTF_ID_FLAGS(func, bpf_iter_num_new, KF_ITER_NEW | KF_SPINLOCK_SAFE)
+BTF_ID_FLAGS(func, bpf_iter_num_next, KF_ITER_NEXT | KF_RET_NULL | KF_SPINLOCK_SAFE)
+BTF_ID_FLAGS(func, bpf_iter_num_destroy, KF_ITER_DESTROY | KF_SPINLOCK_SAFE)
 BTF_ID_FLAGS(func, bpf_iter_task_vma_new, KF_ITER_NEW | KF_RCU)
 BTF_ID_FLAGS(func, bpf_iter_task_vma_next, KF_ITER_NEXT | KF_RET_NULL)
 BTF_ID_FLAGS(func, bpf_iter_task_vma_destroy, KF_ITER_DESTROY)
@@ -4962,8 +4964,8 @@ BTF_ID_FLAGS(func, bpf_strncasestr);
 #if defined(CONFIG_BPF_LSM) && defined(CONFIG_CGROUPS)
 BTF_ID_FLAGS(func, bpf_cgroup_read_xattr, KF_RCU)
 #endif
-BTF_ID_FLAGS(func, bpf_stream_vprintk, KF_IMPLICIT_ARGS)
-BTF_ID_FLAGS(func, bpf_stream_print_stack, KF_IMPLICIT_ARGS)
+BTF_ID_FLAGS(func, bpf_stream_vprintk, KF_IMPLICIT_ARGS | KF_SPINLOCK_SAFE)
+BTF_ID_FLAGS(func, bpf_stream_print_stack, KF_IMPLICIT_ARGS | KF_SPINLOCK_SAFE)
 BTF_ID_FLAGS(func, bpf_task_work_schedule_signal, KF_IMPLICIT_ARGS)
 BTF_ID_FLAGS(func, bpf_task_work_schedule_resume, KF_IMPLICIT_ARGS)
 BTF_ID_FLAGS(func, bpf_dynptr_from_file)
diff --git a/kernel/bpf/rqspinlock.c b/kernel/bpf/rqspinlock.c
index e4e338cdb437..e527cb425cf4 100644
--- a/kernel/bpf/rqspinlock.c
+++ b/kernel/bpf/rqspinlock.c
@@ -744,10 +744,10 @@ __bpf_kfunc void bpf_res_spin_unlock_irqrestore(struct bpf_res_spin_lock *lock,
 __bpf_kfunc_end_defs();
 
 BTF_KFUNCS_START(rqspinlock_kfunc_ids)
-BTF_ID_FLAGS(func, bpf_res_spin_lock, KF_RET_NULL)
-BTF_ID_FLAGS(func, bpf_res_spin_unlock)
-BTF_ID_FLAGS(func, bpf_res_spin_lock_irqsave, KF_RET_NULL)
-BTF_ID_FLAGS(func, bpf_res_spin_unlock_irqrestore)
+BTF_ID_FLAGS(func, bpf_res_spin_lock, KF_RET_NULL | KF_SPINLOCK_SAFE)
+BTF_ID_FLAGS(func, bpf_res_spin_unlock, KF_SPINLOCK_SAFE)
+BTF_ID_FLAGS(func, bpf_res_spin_lock_irqsave, KF_RET_NULL | KF_SPINLOCK_SAFE)
+BTF_ID_FLAGS(func, bpf_res_spin_unlock_irqrestore, KF_SPINLOCK_SAFE)
 BTF_KFUNCS_END(rqspinlock_kfunc_ids)
 
 static const struct btf_kfunc_id_set rqspinlock_kfunc_set = {
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 8daba32306be..d952bd95cbb7 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -11802,20 +11802,6 @@ static bool is_bpf_rbtree_api_kfunc(u32 btf_id)
 	       btf_id == special_kfunc_list[KF_bpf_rbtree_right];
 }
 
-static bool is_bpf_iter_num_api_kfunc(u32 btf_id)
-{
-	return btf_id == special_kfunc_list[KF_bpf_iter_num_new] ||
-	       btf_id == special_kfunc_list[KF_bpf_iter_num_next] ||
-	       btf_id == special_kfunc_list[KF_bpf_iter_num_destroy];
-}
-
-static bool is_bpf_graph_api_kfunc(u32 btf_id)
-{
-	return is_bpf_list_api_kfunc(btf_id) ||
-	       is_bpf_rbtree_api_kfunc(btf_id) ||
-	       is_bpf_refcount_acquire_kfunc(btf_id);
-}
-
 static bool is_bpf_res_spin_lock_kfunc(u32 btf_id)
 {
 	return btf_id == special_kfunc_list[KF_bpf_res_spin_lock] ||
@@ -11824,29 +11810,11 @@ static bool is_bpf_res_spin_lock_kfunc(u32 btf_id)
 	       btf_id == special_kfunc_list[KF_bpf_res_spin_unlock_irqrestore];
 }
 
-static bool is_bpf_arena_kfunc(u32 btf_id)
-{
-	return btf_id == special_kfunc_list[KF_bpf_arena_alloc_pages] ||
-	       btf_id == special_kfunc_list[KF_bpf_arena_free_pages] ||
-	       btf_id == special_kfunc_list[KF_bpf_arena_reserve_pages];
-}
-
-static bool is_bpf_stream_kfunc(u32 btf_id)
-{
-	return btf_id == special_kfunc_list[KF_bpf_stream_vprintk] ||
-	       btf_id == special_kfunc_list[KF_bpf_stream_print_stack];
-}
-
 static bool kfunc_spin_allowed(struct bpf_verifier_env *env, s32 func_id, s16 offset)
 {
 	struct bpf_kfunc_meta kfunc;
 	int err;
 
-	if (is_bpf_graph_api_kfunc(func_id) || is_bpf_iter_num_api_kfunc(func_id) ||
-	    is_bpf_res_spin_lock_kfunc(func_id) || is_bpf_arena_kfunc(func_id) ||
-	    is_bpf_stream_kfunc(func_id))
-		return true;
-
 	err = fetch_kfunc_meta(env, func_id, offset, &kfunc);
 	if (err || !kfunc.flags)
 		return false;