From 089b19a9204fc090793d389a265f54124eacb05d Mon Sep 17 00:00:00 2001 From: Stanislav Fomichev Date: Mon, 22 Apr 2019 08:55:44 -0700 Subject: flow_dissector: switch kernel context to struct bpf_flow_dissector struct bpf_flow_dissector has a small subset of sk_buff fields that flow dissector BPF program is allowed to access and an optional pointer to real skb. Real skb is used only in bpf_skb_load_bytes helper to read non-linear data. The real motivation for this is to be able to call flow dissector from eth_get_headlen context where we don't have an skb and need to dissect raw bytes. Signed-off-by: Stanislav Fomichev Signed-off-by: Daniel Borkmann --- include/linux/skbuff.h | 4 ++ include/net/flow_dissector.h | 7 +++ include/net/sch_generic.h | 11 ++--- net/bpf/test_run.c | 4 -- net/core/filter.c | 105 +++++++++++++++++++++++++++++++++---------- net/core/flow_dissector.c | 45 +++++++++---------- 6 files changed, 117 insertions(+), 59 deletions(-) diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index 6f42942a443b..2b7b8228c5c3 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -1275,6 +1275,10 @@ static inline int skb_flow_dissector_bpf_prog_detach(const union bpf_attr *attr) } #endif +struct bpf_flow_dissector; +bool bpf_flow_dissect(struct bpf_prog *prog, struct bpf_flow_dissector *ctx, + __be16 proto, int nhoff, int hlen); + struct bpf_flow_keys; bool __skb_flow_bpf_dissect(struct bpf_prog *prog, const struct sk_buff *skb, diff --git a/include/net/flow_dissector.h b/include/net/flow_dissector.h index 2b26979efb48..7c5a8d9a8d2a 100644 --- a/include/net/flow_dissector.h +++ b/include/net/flow_dissector.h @@ -305,4 +305,11 @@ static inline void *skb_flow_dissector_target(struct flow_dissector *flow_dissec return ((char *)target_container) + flow_dissector->offset[key_id]; } +struct bpf_flow_dissector { + struct bpf_flow_keys *flow_keys; + const struct sk_buff *skb; + void *data; + void *data_end; +}; + #endif diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h index e8f85cd2afce..21f434f3ac9e 100644 --- a/include/net/sch_generic.h +++ b/include/net/sch_generic.h @@ -364,13 +364,10 @@ struct tcf_proto { }; struct qdisc_skb_cb { - union { - struct { - unsigned int pkt_len; - u16 slave_dev_queue_mapping; - u16 tc_classid; - }; - struct bpf_flow_keys *flow_keys; + struct { + unsigned int pkt_len; + u16 slave_dev_queue_mapping; + u16 tc_classid; }; #define QDISC_CB_PRIV_LEN 20 unsigned char data[QDISC_CB_PRIV_LEN]; diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c index 2221573dacdb..006ad865f7fb 100644 --- a/net/bpf/test_run.c +++ b/net/bpf/test_run.c @@ -382,7 +382,6 @@ int bpf_prog_test_run_flow_dissector(struct bpf_prog *prog, u32 repeat = kattr->test.repeat; struct bpf_flow_keys flow_keys; u64 time_start, time_spent = 0; - struct bpf_skb_data_end *cb; u32 retval, duration; struct sk_buff *skb; struct sock *sk; @@ -423,9 +422,6 @@ int bpf_prog_test_run_flow_dissector(struct bpf_prog *prog, current->nsproxy->net_ns->loopback_dev); skb_reset_network_header(skb); - cb = (struct bpf_skb_data_end *)skb->cb; - cb->qdisc_cb.flow_keys = &flow_keys; - if (!repeat) repeat = 1; diff --git a/net/core/filter.c b/net/core/filter.c index fa8fb0548217..edb3a7c22f6c 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -1730,6 +1730,40 @@ static const struct bpf_func_proto bpf_skb_load_bytes_proto = { .arg4_type = ARG_CONST_SIZE, }; +BPF_CALL_4(bpf_flow_dissector_load_bytes, + const struct bpf_flow_dissector *, ctx, u32, offset, + void *, to, u32, len) +{ + void *ptr; + + if (unlikely(offset > 0xffff)) + goto err_clear; + + if (unlikely(!ctx->skb)) + goto err_clear; + + ptr = skb_header_pointer(ctx->skb, offset, len, to); + if (unlikely(!ptr)) + goto err_clear; + if (ptr != to) + memcpy(to, ptr, len); + + return 0; +err_clear: + memset(to, 0, len); + return -EFAULT; +} + +static const struct bpf_func_proto bpf_flow_dissector_load_bytes_proto = { + .func = bpf_flow_dissector_load_bytes, + .gpl_only = false, + .ret_type = RET_INTEGER, + .arg1_type = ARG_PTR_TO_CTX, + .arg2_type = ARG_ANYTHING, + .arg3_type = ARG_PTR_TO_UNINIT_MEM, + .arg4_type = ARG_CONST_SIZE, +}; + BPF_CALL_5(bpf_skb_load_bytes_relative, const struct sk_buff *, skb, u32, offset, void *, to, u32, len, u32, start_header) { @@ -6121,7 +6155,7 @@ flow_dissector_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) { switch (func_id) { case BPF_FUNC_skb_load_bytes: - return &bpf_skb_load_bytes_proto; + return &bpf_flow_dissector_load_bytes_proto; default: return bpf_base_func_proto(func_id); } @@ -6248,9 +6282,7 @@ static bool bpf_skb_is_valid_access(int off, int size, enum bpf_access_type type return false; break; case bpf_ctx_range_ptr(struct __sk_buff, flow_keys): - if (size != sizeof(__u64)) - return false; - break; + return false; case bpf_ctx_range(struct __sk_buff, tstamp): if (size != sizeof(__u64)) return false; @@ -6285,7 +6317,6 @@ static bool sk_filter_is_valid_access(int off, int size, case bpf_ctx_range(struct __sk_buff, data): case bpf_ctx_range(struct __sk_buff, data_meta): case bpf_ctx_range(struct __sk_buff, data_end): - case bpf_ctx_range_ptr(struct __sk_buff, flow_keys): case bpf_ctx_range_till(struct __sk_buff, family, local_port): case bpf_ctx_range(struct __sk_buff, tstamp): case bpf_ctx_range(struct __sk_buff, wire_len): @@ -6312,7 +6343,6 @@ static bool cg_skb_is_valid_access(int off, int size, switch (off) { case bpf_ctx_range(struct __sk_buff, tc_classid): case bpf_ctx_range(struct __sk_buff, data_meta): - case bpf_ctx_range_ptr(struct __sk_buff, flow_keys): case bpf_ctx_range(struct __sk_buff, wire_len): return false; case bpf_ctx_range(struct __sk_buff, data): @@ -6358,7 +6388,6 @@ static bool lwt_is_valid_access(int off, int size, case bpf_ctx_range(struct __sk_buff, tc_classid): case bpf_ctx_range_till(struct __sk_buff, family, local_port): case bpf_ctx_range(struct __sk_buff, data_meta): - case bpf_ctx_range_ptr(struct __sk_buff, flow_keys): case bpf_ctx_range(struct __sk_buff, tstamp): case bpf_ctx_range(struct __sk_buff, wire_len): return false; @@ -6601,7 +6630,6 @@ static bool tc_cls_act_is_valid_access(int off, int size, case bpf_ctx_range(struct __sk_buff, data_end): info->reg_type = PTR_TO_PACKET_END; break; - case bpf_ctx_range_ptr(struct __sk_buff, flow_keys): case bpf_ctx_range_till(struct __sk_buff, family, local_port): return false; } @@ -6803,7 +6831,6 @@ static bool sk_skb_is_valid_access(int off, int size, switch (off) { case bpf_ctx_range(struct __sk_buff, tc_classid): case bpf_ctx_range(struct __sk_buff, data_meta): - case bpf_ctx_range_ptr(struct __sk_buff, flow_keys): case bpf_ctx_range(struct __sk_buff, tstamp): case bpf_ctx_range(struct __sk_buff, wire_len): return false; @@ -6877,24 +6904,65 @@ static bool flow_dissector_is_valid_access(int off, int size, const struct bpf_prog *prog, struct bpf_insn_access_aux *info) { + const int size_default = sizeof(__u32); + + if (off < 0 || off >= sizeof(struct __sk_buff)) + return false; + if (type == BPF_WRITE) return false; switch (off) { case bpf_ctx_range(struct __sk_buff, data): + if (size != size_default) + return false; info->reg_type = PTR_TO_PACKET; - break; + return true; case bpf_ctx_range(struct __sk_buff, data_end): + if (size != size_default) + return false; info->reg_type = PTR_TO_PACKET_END; - break; + return true; case bpf_ctx_range_ptr(struct __sk_buff, flow_keys): + if (size != sizeof(__u64)) + return false; info->reg_type = PTR_TO_FLOW_KEYS; - break; + return true; default: return false; } +} - return bpf_skb_is_valid_access(off, size, type, prog, info); +static u32 flow_dissector_convert_ctx_access(enum bpf_access_type type, + const struct bpf_insn *si, + struct bpf_insn *insn_buf, + struct bpf_prog *prog, + u32 *target_size) + +{ + struct bpf_insn *insn = insn_buf; + + switch (si->off) { + case offsetof(struct __sk_buff, data): + *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct bpf_flow_dissector, data), + si->dst_reg, si->src_reg, + offsetof(struct bpf_flow_dissector, data)); + break; + + case offsetof(struct __sk_buff, data_end): + *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct bpf_flow_dissector, data_end), + si->dst_reg, si->src_reg, + offsetof(struct bpf_flow_dissector, data_end)); + break; + + case offsetof(struct __sk_buff, flow_keys): + *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct bpf_flow_dissector, flow_keys), + si->dst_reg, si->src_reg, + offsetof(struct bpf_flow_dissector, flow_keys)); + break; + } + + return insn - insn_buf; } static u32 bpf_convert_ctx_access(enum bpf_access_type type, @@ -7201,15 +7269,6 @@ static u32 bpf_convert_ctx_access(enum bpf_access_type type, skc_num, 2, target_size)); break; - case offsetof(struct __sk_buff, flow_keys): - off = si->off; - off -= offsetof(struct __sk_buff, flow_keys); - off += offsetof(struct sk_buff, cb); - off += offsetof(struct qdisc_skb_cb, flow_keys); - *insn++ = BPF_LDX_MEM(BPF_SIZEOF(void *), si->dst_reg, - si->src_reg, off); - break; - case offsetof(struct __sk_buff, tstamp): BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, tstamp) != 8); @@ -8214,7 +8273,7 @@ const struct bpf_prog_ops sk_msg_prog_ops = { const struct bpf_verifier_ops flow_dissector_verifier_ops = { .get_func_proto = flow_dissector_func_proto, .is_valid_access = flow_dissector_is_valid_access, - .convert_ctx_access = bpf_convert_ctx_access, + .convert_ctx_access = flow_dissector_convert_ctx_access, }; const struct bpf_prog_ops flow_dissector_prog_ops = { diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c index 795449713ba4..ef6d9443cc75 100644 --- a/net/core/flow_dissector.c +++ b/net/core/flow_dissector.c @@ -688,39 +688,34 @@ bool __skb_flow_bpf_dissect(struct bpf_prog *prog, struct flow_dissector *flow_dissector, struct bpf_flow_keys *flow_keys) { - struct bpf_skb_data_end cb_saved; - struct bpf_skb_data_end *cb; - u32 result; - - /* Note that even though the const qualifier is discarded - * throughout the execution of the BPF program, all changes(the - * control block) are reverted after the BPF program returns. - * Therefore, __skb_flow_dissect does not alter the skb. - */ - - cb = (struct bpf_skb_data_end *)skb->cb; + struct bpf_flow_dissector ctx = { + .flow_keys = flow_keys, + .skb = skb, + .data = skb->data, + .data_end = skb->data + skb_headlen(skb), + }; + + return bpf_flow_dissect(prog, &ctx, skb->protocol, + skb_network_offset(skb), skb_headlen(skb)); +} - /* Save Control Block */ - memcpy(&cb_saved, cb, sizeof(cb_saved)); - memset(cb, 0, sizeof(*cb)); +bool bpf_flow_dissect(struct bpf_prog *prog, struct bpf_flow_dissector *ctx, + __be16 proto, int nhoff, int hlen) +{ + struct bpf_flow_keys *flow_keys = ctx->flow_keys; + u32 result; /* Pass parameters to the BPF program */ memset(flow_keys, 0, sizeof(*flow_keys)); - cb->qdisc_cb.flow_keys = flow_keys; - flow_keys->n_proto = skb->protocol; - flow_keys->nhoff = skb_network_offset(skb); + flow_keys->n_proto = proto; + flow_keys->nhoff = nhoff; flow_keys->thoff = flow_keys->nhoff; - bpf_compute_data_pointers((struct sk_buff *)skb); - result = BPF_PROG_RUN(prog, skb); - - /* Restore state */ - memcpy(cb, &cb_saved, sizeof(cb_saved)); + result = BPF_PROG_RUN(prog, ctx); - flow_keys->nhoff = clamp_t(u16, flow_keys->nhoff, - skb_network_offset(skb), skb->len); + flow_keys->nhoff = clamp_t(u16, flow_keys->nhoff, nhoff, hlen); flow_keys->thoff = clamp_t(u16, flow_keys->thoff, - flow_keys->nhoff, skb->len); + flow_keys->nhoff, hlen); return result == BPF_OK; } -- cgit v1.2.3-59-g8ed1b