diff options
Diffstat (limited to 'include/linux/bpf_verifier.h')
| -rw-r--r-- | include/linux/bpf_verifier.h | 40 |
1 files changed, 40 insertions, 0 deletions
diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h index 69f7a3449eda..7d8228d1c898 100644 --- a/include/linux/bpf_verifier.h +++ b/include/linux/bpf_verifier.h @@ -66,6 +66,46 @@ struct bpf_reg_state { * same reference to the socket, to determine proper reference freeing. */ u32 id; + /* PTR_TO_SOCKET and PTR_TO_TCP_SOCK could be a ptr returned + * from a pointer-cast helper, bpf_sk_fullsock() and + * bpf_tcp_sock(). + * + * Consider the following where "sk" is a reference counted + * pointer returned from "sk = bpf_sk_lookup_tcp();": + * + * 1: sk = bpf_sk_lookup_tcp(); + * 2: if (!sk) { return 0; } + * 3: fullsock = bpf_sk_fullsock(sk); + * 4: if (!fullsock) { bpf_sk_release(sk); return 0; } + * 5: tp = bpf_tcp_sock(fullsock); + * 6: if (!tp) { bpf_sk_release(sk); return 0; } + * 7: bpf_sk_release(sk); + * 8: snd_cwnd = tp->snd_cwnd; // verifier will complain + * + * After bpf_sk_release(sk) at line 7, both "fullsock" ptr and + * "tp" ptr should be invalidated also. In order to do that, + * the reg holding "fullsock" and "sk" need to remember + * the original refcounted ptr id (i.e. sk_reg->id) in ref_obj_id + * such that the verifier can reset all regs which have + * ref_obj_id matching the sk_reg->id. + * + * sk_reg->ref_obj_id is set to sk_reg->id at line 1. + * sk_reg->id will stay as NULL-marking purpose only. + * After NULL-marking is done, sk_reg->id can be reset to 0. + * + * After "fullsock = bpf_sk_fullsock(sk);" at line 3, + * fullsock_reg->ref_obj_id is set to sk_reg->ref_obj_id. + * + * After "tp = bpf_tcp_sock(fullsock);" at line 5, + * tp_reg->ref_obj_id is set to fullsock_reg->ref_obj_id + * which is the same as sk_reg->ref_obj_id. + * + * From the verifier perspective, if sk, fullsock and tp + * are not NULL, they are the same ptr with different + * reg->type. In particular, bpf_sk_release(tp) is also + * allowed and has the same effect as bpf_sk_release(sk). + */ + u32 ref_obj_id; /* For scalar types (SCALAR_VALUE), this represents our knowledge of * the actual value. * For pointer types, this represents the variable part of the offset |