There is a constant need to add more fields into the bpf_tcp_sock
for the bpf programs running at tc, sock_ops...etc.
A current workaround could be to use bpf_probe_read_kernel(). However,
other than making another helper call for reading each field and missing
CO-RE, it is also not as intuitive to use as directly reading
"tp->lsndtime" for example. While already having perfmon cap to do
bpf_probe_read_kernel(), it will be much easier if the bpf prog can
directly read from the tcp_sock.
This patch tries to do that by using the existing casting-helpers
bpf_skc_to_*() whose func_proto returns a btf_id. For example, the
func_proto of bpf_skc_to_tcp_sock returns the btf_id of the
kernel "struct tcp_sock".
These helpers are also added to is_ptr_cast_function().
It ensures the returning reg (BPF_REF_0) will also carries the ref_obj_id.
That will keep the ref-tracking works properly.
The bpf_skc_to_* helpers are made available to most of the bpf prog
types in filter.c. They are limited by perfmon cap.
This patch adds a ARG_PTR_TO_BTF_ID_SOCK_COMMON. The helper accepting
this arg can accept a btf-id-ptr (PTR_TO_BTF_ID + &btf_sock_ids[BTF_SOCK_TYPE_SOCK_COMMON])
or a legacy-ctx-convert-skc-ptr (PTR_TO_SOCK_COMMON). The bpf_skc_to_*()
helpers are changed to take ARG_PTR_TO_BTF_ID_SOCK_COMMON such that
they will accept pointer obtained from skb->sk.
PTR_TO_*_OR_NULL is not accepted as an ARG_PTR_TO_BTF_ID_SOCK_COMMON
at verification time. All PTR_TO_*_OR_NULL reg has to do a NULL check
first before passing into the helper or else the bpf prog will be
rejected by the verifier.
[ ARG_PTR_TO_SOCK_COMMON_OR_NULL was attempted earlier. The _OR_NULL was
needed because the PTR_TO_BTF_ID could be NULL but note that a could be NULL
PTR_TO_BTF_ID is not a scalar NULL to the verifier. "_OR_NULL" implicitly
gives an expectation that the helper can take a scalar NULL which does
not make sense in most (except one) helpers. Passing scalar NULL
should be rejected at the verification time.
Thus, this patch uses ARG_PTR_TO_BTF_ID_SOCK_COMMON to specify that the
helper can take both the btf-id ptr or the legacy PTR_TO_SOCK_COMMON but
not scalar NULL. It requires the func_proto to explicitly specify the
arg_btf_id such that there is a very clear expectation that the helper
can handle a NULL PTR_TO_BTF_ID. ]
[ ARG_PTR_TO_BTF_ID_SOCK_COMMON will be used to replace
ARG_PTR_TO_SOCK* of other existing helpers later such that
those existing helpers can take the PTR_TO_BTF_ID returned by
the bpf_skc_to_*() helpers.
The only special case is bpf_sk_lookup_assign() which can accept a
scalar NULL ptr. It has to be handled specially in another follow
up patch (e.g. by renaming ARG_PTR_TO_SOCKET_OR_NULL to
ARG_PTR_TO_BTF_ID_SOCK_COMMON_OR_NULL). ]
[ When converting the older helpers that take ARG_PTR_TO_SOCK* in
the later patch, if the kernel does not support BTF,
ARG_PTR_TO_BTF_ID_SOCK_COMMON will behave like ARG_PTR_TO_SOCK_COMMON
because no reg->type could have PTR_TO_BTF_ID in this case.
It is not a concern for the newer-btf-only helper like the bpf_skc_to_*()
here though because these helpers must require BTF vmlinux to begin
with. ]
Signed-off-by: Martin KaFai Lau <kafai@xxxxxx>
---
include/linux/bpf.h | 1 +
kernel/bpf/verifier.c | 28 ++++++++++++++++---
net/core/filter.c | 64 +++++++++++++++++++++++++++++++++----------
3 files changed, 74 insertions(+), 19 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index fc5c901c7542..d0937f1d2980 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -292,6 +292,7 @@ enum bpf_arg_type {
ARG_PTR_TO_ALLOC_MEM, /* pointer to dynamically allocated memory */
ARG_PTR_TO_ALLOC_MEM_OR_NULL, /* pointer to dynamically allocated memory or NULL */
ARG_CONST_ALLOC_SIZE_OR_ZERO, /* number of allocated bytes requested */
+ ARG_PTR_TO_BTF_ID_SOCK_COMMON, /* pointer to in-kernel sock_common or bpf-mirrored bpf_sock */
__BPF_ARG_TYPE_MAX,
};
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 3ce61c412ea0..2468533bc4a1 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -486,7 +486,12 @@ static bool is_acquire_function(enum bpf_func_id func_id,
static bool is_ptr_cast_function(enum bpf_func_id func_id)
{
return func_id == BPF_FUNC_tcp_sock ||
- func_id == BPF_FUNC_sk_fullsock;
+ func_id == BPF_FUNC_sk_fullsock ||
+ func_id == BPF_FUNC_skc_to_tcp_sock ||
+ func_id == BPF_FUNC_skc_to_tcp6_sock ||
+ func_id == BPF_FUNC_skc_to_udp6_sock ||
+ func_id == BPF_FUNC_skc_to_tcp_timewait_sock ||
+ func_id == BPF_FUNC_skc_to_tcp_request_sock;
}
/* string representation of 'enum bpf_reg_type' */
@@ -3973,6 +3978,16 @@ static const struct bpf_reg_types sock_types = {
},
};
+static const struct bpf_reg_types btf_id_sock_common_types = {
+ .types = {
+ PTR_TO_SOCK_COMMON,
+ PTR_TO_SOCKET,
+ PTR_TO_TCP_SOCK,
+ PTR_TO_XDP_SOCK,
+ PTR_TO_BTF_ID,
+ },
+};
+
static const struct bpf_reg_types mem_types = {
.types = {
PTR_TO_STACK,
@@ -4014,6 +4029,7 @@ static const struct bpf_reg_types *compatible_reg_types[] = {
[ARG_PTR_TO_CTX] = &context_types,
[ARG_PTR_TO_CTX_OR_NULL] = &context_types,
[ARG_PTR_TO_SOCK_COMMON] = &sock_types,
+ [ARG_PTR_TO_BTF_ID_SOCK_COMMON] = &btf_id_sock_common_types,
[ARG_PTR_TO_SOCKET] = &fullsock_types,
[ARG_PTR_TO_SOCKET_OR_NULL] = &fullsock_types,
[ARG_PTR_TO_BTF_ID] = &btf_ptr_types,
@@ -4579,9 +4595,13 @@ static bool check_btf_id_ok(const struct bpf_func_proto *fn)
{
int i;
- for (i = 0; i < ARRAY_SIZE(fn->arg_type); i++)
- if (fn->arg_type[i] == ARG_PTR_TO_BTF_ID && !fn->arg_btf_id[i])
- return false;
+ for (i = 0; i < ARRAY_SIZE(fn->arg_type); i++) {
+ if (fn->arg_type[i] == ARG_PTR_TO_BTF_ID ||
+ fn->arg_type[i] == ARG_PTR_TO_BTF_ID_SOCK_COMMON) {
+ if (!fn->arg_btf_id[i])
+ return false;
+ }
+ }
return true;
}
diff --git a/net/core/filter.c b/net/core/filter.c
index 6014e5f40c58..54b338de4bb8 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -77,6 +77,9 @@
#include <net/transp_v6.h>
#include <linux/btf_ids.h>
+static const struct bpf_func_proto *
+bpf_sk_base_func_proto(enum bpf_func_id func_id);
+
int copy_bpf_fprog_from_user(struct sock_fprog *dst, sockptr_t src, int len)
{
if (in_compat_syscall()) {
@@ -6619,7 +6622,7 @@ sock_addr_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
return NULL;
}
default:
- return bpf_base_func_proto(func_id);
+ return bpf_sk_base_func_proto(func_id);
}
}
@@ -6638,7 +6641,7 @@ sk_filter_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
case BPF_FUNC_perf_event_output:
return &bpf_skb_event_output_proto;
default:
- return bpf_base_func_proto(func_id);
+ return bpf_sk_base_func_proto(func_id);
}
}
@@ -6799,7 +6802,7 @@ tc_cls_act_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
return &bpf_sk_assign_proto;
#endif
default:
- return bpf_base_func_proto(func_id);
+ return bpf_sk_base_func_proto(func_id);
}
}
@@ -6840,7 +6843,7 @@ xdp_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
return &bpf_tcp_gen_syncookie_proto;
#endif
default:
- return bpf_base_func_proto(func_id);
+ return bpf_sk_base_func_proto(func_id);
}
}
@@ -6882,7 +6885,7 @@ sock_ops_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
return &bpf_tcp_sock_proto;
#endif /* CONFIG_INET */
default:
- return bpf_base_func_proto(func_id);
+ return bpf_sk_base_func_proto(func_id);
}
}
@@ -6928,7 +6931,7 @@ sk_msg_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
return &bpf_get_cgroup_classid_curr_proto;
#endif
default:
- return bpf_base_func_proto(func_id);
+ return bpf_sk_base_func_proto(func_id);
}
}
@@ -6970,7 +6973,7 @@ sk_skb_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
return &bpf_skc_lookup_tcp_proto;
#endif
default:
- return bpf_base_func_proto(func_id);
+ return bpf_sk_base_func_proto(func_id);
}
}
@@ -6981,7 +6984,7 @@ flow_dissector_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
case BPF_FUNC_skb_load_bytes:
return &bpf_flow_dissector_load_bytes_proto;
default:
- return bpf_base_func_proto(func_id);
+ return bpf_sk_base_func_proto(func_id);
}
}
@@ -7008,7 +7011,7 @@ lwt_out_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
case BPF_FUNC_skb_under_cgroup:
return &bpf_skb_under_cgroup_proto;
default:
- return bpf_base_func_proto(func_id);
+ return bpf_sk_base_func_proto(func_id);
}
}
@@ -9745,7 +9748,7 @@ sk_lookup_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
case BPF_FUNC_sk_release:
return &bpf_sk_release_proto;
default:
- return bpf_base_func_proto(func_id);
+ return bpf_sk_base_func_proto(func_id);
}
}
@@ -9912,7 +9915,7 @@ const struct bpf_func_proto bpf_skc_to_tcp6_sock_proto = {
.func = bpf_skc_to_tcp6_sock,
.gpl_only = false,
.ret_type = RET_PTR_TO_BTF_ID_OR_NULL,
- .arg1_type = ARG_PTR_TO_BTF_ID,
+ .arg1_type = ARG_PTR_TO_BTF_ID_SOCK_COMMON,
.arg1_btf_id = &btf_sock_ids[BTF_SOCK_TYPE_SOCK_COMMON],
.ret_btf_id = &btf_sock_ids[BTF_SOCK_TYPE_TCP6],
};
@@ -9929,7 +9932,7 @@ const struct bpf_func_proto bpf_skc_to_tcp_sock_proto = {
.func = bpf_skc_to_tcp_sock,
.gpl_only = false,
.ret_type = RET_PTR_TO_BTF_ID_OR_NULL,
- .arg1_type = ARG_PTR_TO_BTF_ID,
+ .arg1_type = ARG_PTR_TO_BTF_ID_SOCK_COMMON,
.arg1_btf_id = &btf_sock_ids[BTF_SOCK_TYPE_SOCK_COMMON],
.ret_btf_id = &btf_sock_ids[BTF_SOCK_TYPE_TCP],
};
@@ -9953,7 +9956,7 @@ const struct bpf_func_proto bpf_skc_to_tcp_timewait_sock_proto = {
.func = bpf_skc_to_tcp_timewait_sock,
.gpl_only = false,
.ret_type = RET_PTR_TO_BTF_ID_OR_NULL,
- .arg1_type = ARG_PTR_TO_BTF_ID,
+ .arg1_type = ARG_PTR_TO_BTF_ID_SOCK_COMMON,
.arg1_btf_id = &btf_sock_ids[BTF_SOCK_TYPE_SOCK_COMMON],
.ret_btf_id = &btf_sock_ids[BTF_SOCK_TYPE_TCP_TW],
};
@@ -9977,7 +9980,7 @@ const struct bpf_func_proto bpf_skc_to_tcp_request_sock_proto = {
.func = bpf_skc_to_tcp_request_sock,
.gpl_only = false,
.ret_type = RET_PTR_TO_BTF_ID_OR_NULL,
- .arg1_type = ARG_PTR_TO_BTF_ID,
+ .arg1_type = ARG_PTR_TO_BTF_ID_SOCK_COMMON,
.arg1_btf_id = &btf_sock_ids[BTF_SOCK_TYPE_SOCK_COMMON],
.ret_btf_id = &btf_sock_ids[BTF_SOCK_TYPE_TCP_REQ],
};
@@ -9999,7 +10002,38 @@ const struct bpf_func_proto bpf_skc_to_udp6_sock_proto = {
.func = bpf_skc_to_udp6_sock,
.gpl_only = false,
.ret_type = RET_PTR_TO_BTF_ID_OR_NULL,
- .arg1_type = ARG_PTR_TO_BTF_ID,
+ .arg1_type = ARG_PTR_TO_BTF_ID_SOCK_COMMON,
.arg1_btf_id = &btf_sock_ids[BTF_SOCK_TYPE_SOCK_COMMON],
.ret_btf_id = &btf_sock_ids[BTF_SOCK_TYPE_UDP6],
};
+
+static const struct bpf_func_proto *
+bpf_sk_base_func_proto(enum bpf_func_id func_id)
+{
+ const struct bpf_func_proto *func;
+
+ switch (func_id) {
+ case BPF_FUNC_skc_to_tcp6_sock:
+ func = &bpf_skc_to_tcp6_sock_proto;
+ break;
+ case BPF_FUNC_skc_to_tcp_sock:
+ func = &bpf_skc_to_tcp_sock_proto;
+ break;
+ case BPF_FUNC_skc_to_tcp_timewait_sock:
+ func = &bpf_skc_to_tcp_timewait_sock_proto;
+ break;
+ case BPF_FUNC_skc_to_tcp_request_sock:
+ func = &bpf_skc_to_tcp_request_sock_proto;
+ break;
+ case BPF_FUNC_skc_to_udp6_sock:
+ func = &bpf_skc_to_udp6_sock_proto;
+ break;
+ default:
+ return bpf_base_func_proto(func_id);
+ }
+
+ if (!perfmon_capable())
+ return NULL;
+
+ return func;
+}
--
2.24.1
