Commit 39f77533 authored by Emil Tsalapatis's avatar Emil Tsalapatis Committed by Alexei Starovoitov
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bpf: Allow calls to arena functions while holding spinlocks 



The bpf_arena_*_pages() kfuncs can be called from sleepable contexts,
but the verifier still prevents BPF programs from calling them while
holding a spinlock. Amend the verifier to allow for BPF programs
calling arena page management functions while holding a lock.

Signed-off-by: default avatarEmil Tsalapatis <emil@etsalapatis.com>
Link: https://lore.kernel.org/r/20260106-arena-under-lock-v2-2-378e9eab3066@etsalapatis.com


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent b25b48c7

kernel/bpf/verifier.c

+10 −1
Original line number Diff line number Diff line
@@ -12373,6 +12373,7 @@ enum special_kfunc_type { 
	KF_bpf_task_work_schedule_resume_impl,

	KF_bpf_arena_alloc_pages,

	KF_bpf_arena_free_pages,

	KF_bpf_arena_reserve_pages,

};









BTF_ID_LIST(special_kfunc_list)








@@ -12449,6 +12450,7 @@ BTF_ID(func, bpf_task_work_schedule_signal_impl)







BTF_ID(func, bpf_task_work_schedule_resume_impl)









BTF_ID(func, bpf_arena_alloc_pages)









BTF_ID(func, bpf_arena_free_pages)









BTF_ID(func, bpf_arena_reserve_pages)

















static bool is_task_work_add_kfunc(u32 func_id)









{








@@ -12884,10 +12886,17 @@ 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 kfunc_spin_allowed(u32 btf_id)









{









	return is_bpf_graph_api_kfunc(btf_id) || is_bpf_iter_num_api_kfunc(btf_id) ||









	       is_bpf_res_spin_lock_kfunc(btf_id);









	       is_bpf_res_spin_lock_kfunc(btf_id) || is_bpf_arena_kfunc(btf_id);









}

















static bool is_sync_callback_calling_kfunc(u32 btf_id)