Commit da03e43a authored by Kumar Kartikeya Dwivedi's avatar Kumar Kartikeya Dwivedi Committed by Alexei Starovoitov
Browse files

bpf: Fix check_reg_type for PTR_TO_BTF_ID 

The current code does type matching for the case where reg->type is
PTR_TO_BTF_ID or has the PTR_TRUSTED flag. However, this only needs to
occur for non-MEM_ALLOC and non-MEM_PERCPU cases, but will include both
as per the current code.

The MEM_ALLOC case with or without PTR_TRUSTED needs to be handled
specially by the code for type_is_alloc case, while MEM_PERCPU case must
be ignored. Hence, to restore correct behavior and for clarity,
explicitly list out the handled PTR_TO_BTF_ID types which should be
handled for each case using a switch statement.

Helpers currently only take:
	PTR_TO_BTF_ID
	PTR_TO_BTF_ID | PTR_TRUSTED
	PTR_TO_BTF_ID | MEM_RCU
	PTR_TO_BTF_ID | MEM_ALLOC
	PTR_TO_BTF_ID | MEM_PERCPU
	PTR_TO_BTF_ID | MEM_PERCPU | PTR_TRUSTED

This fix was also described (for the MEM_ALLOC case) in [0].

  [0]: https://lore.kernel.org/bpf/20221121160657.h6z7xuvedybp5y7s@apollo



Signed-off-by: default avatarKumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20230221200646.2500777-6-memxor@gmail.com


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 521d3c0a

kernel/bpf/verifier.c

+20 −3
Original line number Diff line number Diff line
@@ -6527,7 +6527,14 @@ static int check_reg_type(struct bpf_verifier_env *env, u32 regno, 
	return -EACCES;









found:









	if (reg->type == PTR_TO_BTF_ID || reg->type & PTR_TRUSTED) {









	if (base_type(reg->type) != PTR_TO_BTF_ID)









		return 0;

















	switch ((int)reg->type) {









	case PTR_TO_BTF_ID:









	case PTR_TO_BTF_ID | PTR_TRUSTED:









	case PTR_TO_BTF_ID | MEM_RCU:









	{









		/* For bpf_sk_release, it needs to match against first member









		 * 'struct sock_common', hence make an exception for it. This









		 * allows bpf_sk_release to work for multiple socket types.








@@ -6563,13 +6570,23 @@ static int check_reg_type(struct bpf_verifier_env *env, u32 regno,







				return -EACCES;









			}









		}









	} else if (type_is_alloc(reg->type)) {









		break;









	}









	case PTR_TO_BTF_ID | MEM_ALLOC:









		if (meta->func_id != BPF_FUNC_spin_lock && meta->func_id != BPF_FUNC_spin_unlock) {









			verbose(env, "verifier internal error: unimplemented handling of MEM_ALLOC\n");









			return -EFAULT;









		}









		/* Handled by helper specific checks */









		break;









	case PTR_TO_BTF_ID | MEM_PERCPU:









	case PTR_TO_BTF_ID | MEM_PERCPU | PTR_TRUSTED:









		/* Handled by helper specific checks */









		break;









	default:









		verbose(env, "verifier internal error: invalid PTR_TO_BTF_ID register for type match\n");









		return -EFAULT;









	}

















	return 0;









}