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authorStanislav Fomichev <sdf@google.com>2019-04-22 08:55:44 -0700
committerDaniel Borkmann <daniel@iogearbox.net>2019-04-23 18:36:33 +0200
commit089b19a9204fc090793d389a265f54124eacb05d (patch)
tree66e9a7497cc7c7444866bda214ea14bd6b66f1ae /net/core
parent7e6e185c74dd8a8dc539300c079adc6bc27045d6 (diff)
downloadlinux-089b19a9204fc090793d389a265f54124eacb05d.tar.bz2
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 <sdf@google.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Diffstat (limited to 'net/core')
-rw-r--r--net/core/filter.c105
-rw-r--r--net/core/flow_dissector.c45
2 files changed, 102 insertions, 48 deletions
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;
}