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Date: Wed, 16 Jun 2021 16:34:46 -0400
From: Tanner Love <tannerlove.kernel@...il.com>
To: netdev@...r.kernel.org
Cc: davem@...emloft.net, Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Andrii Nakryiko <andrii@...nel.org>,
Eric Dumazet <edumazet@...gle.com>,
Willem de Bruijn <willemb@...gle.com>,
Petar Penkov <ppenkov@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
"Michael S . Tsirkin" <mst@...hat.com>,
Jason Wang <jasowang@...hat.com>,
Martin KaFai Lau <kafai@...com>,
Tanner Love <tannerlove@...gle.com>,
Stanislav Fomichev <sdf@...gle.com>
Subject: [PATCH net-next v7 1/3] net: flow_dissector: extend bpf flow dissector support with vnet hdr
From: Tanner Love <tannerlove@...gle.com>
Amend the bpf flow dissector program type to be able to process
virtio-net headers. Do this to enable bpf flow dissector programs to
perform virtio-net header validation. The next patch in this series
will add a flow dissection hook in virtio_net_hdr_to_skb and make use
of this extended functionality. That commit message has more
background on the use case.
Add a pointer to struct virtio_net_hdr as a new member in struct
bpf_flow_keys. When machine is big and vnet hdr is little endian, the
kernel converts the vnet hdr endianness before passing the vnet hdr
pointer to the bpf program; otherwise, the kernel just passes along
the pointer to the unaltered vnet header to the bpf program. This
handles the case of a v1+ header on a big endian machine.
Changes
v7:
- Remove vhdr_is_little_endian, instead copy vhdr fields only in
case where machine is big and vhdr is little endian
- Rename check_flow_keys_access bpf_flow_dissector_is_valid_access
- Move bpf_flow_dissector_is_valid_access() under CONFIG_NET
- Make bpf_flow_dissector_is_valid_access() populate info.btf and
info.reg_type in addition to info.btf_id
v6:
- Move bpf_flow_dissector_btf_ids, check_flow_keys_access() to
filter.c
- Verify (off % size == 0) in check_flow_keys_access()
- Check bpf_flow_dissector_btf_ids[0] is nonzero in
check_flow_keys_access()
v5:
- Use PTR_TO_BTF_ID_OR_NULL instead of defining new
PTR_TO_VNET_HDR_OR_NULL
- Make check_flow_keys_access() disallow writes to keys->vhdr
- Make check_flow_keys_access() check loading keys->vhdr is in
sizeof(__u64)
- Use BPF_REG_AX instead of BPF_REG_TMP as scratch reg
- Describe parameter vhdr_is_little_endian in __skb_flow_dissect
documentation
v4:
- Add virtio_net_hdr pointer to struct bpf_flow_keys
- Add vhdr_is_little_endian to struct bpf_flow_keys
v2:
- Describe parameter vhdr in __skb_flow_dissect documentation
Signed-off-by: Tanner Love <tannerlove@...gle.com>
Reviewed-by: Willem de Bruijn <willemb@...gle.com>
Reviewed-by: Petar Penkov <ppenkov@...gle.com>
Reviewed-by: Stanislav Fomichev <sdf@...gle.com>
---
drivers/net/bonding/bond_main.c | 2 +-
include/linux/bpf.h | 8 +++++
include/linux/skbuff.h | 35 +++++++++++++++++-----
include/uapi/linux/bpf.h | 1 +
kernel/bpf/verifier.c | 33 ++++++++++----------
net/bpf/test_run.c | 2 +-
net/core/filter.c | 53 +++++++++++++++++++++++++++++++++
net/core/flow_dissector.c | 36 +++++++++++++++++++---
tools/include/uapi/linux/bpf.h | 1 +
9 files changed, 143 insertions(+), 28 deletions(-)
diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index eb79a9f05914..36993636d56d 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -3554,7 +3554,7 @@ static bool bond_flow_dissect(struct bonding *bond, struct sk_buff *skb,
case BOND_XMIT_POLICY_ENCAP34:
memset(fk, 0, sizeof(*fk));
return __skb_flow_dissect(NULL, skb, &flow_keys_bonding,
- fk, NULL, 0, 0, 0, 0);
+ fk, NULL, 0, 0, 0, 0, NULL, false);
default:
break;
}
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 9dc44ba97584..e6980da0b469 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1998,6 +1998,8 @@ u32 bpf_sock_convert_ctx_access(enum bpf_access_type type,
struct bpf_insn *insn_buf,
struct bpf_prog *prog,
u32 *target_size);
+int bpf_flow_keys_is_valid_access(int off, int size, enum bpf_access_type t,
+ struct bpf_insn_access_aux *info);
#else
static inline bool bpf_sock_common_is_valid_access(int off, int size,
enum bpf_access_type type,
@@ -2019,6 +2021,12 @@ static inline u32 bpf_sock_convert_ctx_access(enum bpf_access_type type,
{
return 0;
}
+static inline int bpf_flow_keys_is_valid_access(int off, int size,
+ enum bpf_access_type t,
+ struct bpf_insn_access_aux *info)
+{
+ return -EINVAL;
+}
#endif
#ifdef CONFIG_INET
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index b2db9cd9a73f..4e390cd8f72a 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1314,21 +1314,27 @@ void skb_flow_dissector_init(struct flow_dissector *flow_dissector,
unsigned int key_count);
struct bpf_flow_dissector;
+struct virtio_net_hdr;
bool bpf_flow_dissect(struct bpf_prog *prog, struct bpf_flow_dissector *ctx,
- __be16 proto, int nhoff, int hlen, unsigned int flags);
+ __be16 proto, int nhoff, int hlen, unsigned int flags,
+ const struct virtio_net_hdr *vhdr,
+ bool vhdr_is_little_endian);
bool __skb_flow_dissect(const struct net *net,
const struct sk_buff *skb,
struct flow_dissector *flow_dissector,
void *target_container, const void *data,
- __be16 proto, int nhoff, int hlen, unsigned int flags);
+ __be16 proto, int nhoff, int hlen, unsigned int flags,
+ const struct virtio_net_hdr *vhdr,
+ bool vhdr_is_little_endian);
static inline bool skb_flow_dissect(const struct sk_buff *skb,
struct flow_dissector *flow_dissector,
void *target_container, unsigned int flags)
{
return __skb_flow_dissect(NULL, skb, flow_dissector,
- target_container, NULL, 0, 0, 0, flags);
+ target_container, NULL, 0, 0, 0, flags, NULL,
+ false);
}
static inline bool skb_flow_dissect_flow_keys(const struct sk_buff *skb,
@@ -1337,7 +1343,22 @@ static inline bool skb_flow_dissect_flow_keys(const struct sk_buff *skb,
{
memset(flow, 0, sizeof(*flow));
return __skb_flow_dissect(NULL, skb, &flow_keys_dissector,
- flow, NULL, 0, 0, 0, flags);
+ flow, NULL, 0, 0, 0, flags, NULL, false);
+}
+
+static inline bool
+__skb_flow_dissect_flow_keys_basic(const struct net *net,
+ const struct sk_buff *skb,
+ struct flow_keys_basic *flow,
+ const void *data, __be16 proto,
+ int nhoff, int hlen, unsigned int flags,
+ const struct virtio_net_hdr *vhdr,
+ bool vhdr_is_little_endian)
+{
+ memset(flow, 0, sizeof(*flow));
+ return __skb_flow_dissect(net, skb, &flow_keys_basic_dissector, flow,
+ data, proto, nhoff, hlen, flags, vhdr,
+ vhdr_is_little_endian);
}
static inline bool
@@ -1347,9 +1368,9 @@ skb_flow_dissect_flow_keys_basic(const struct net *net,
const void *data, __be16 proto,
int nhoff, int hlen, unsigned int flags)
{
- memset(flow, 0, sizeof(*flow));
- return __skb_flow_dissect(net, skb, &flow_keys_basic_dissector, flow,
- data, proto, nhoff, hlen, flags);
+ return __skb_flow_dissect_flow_keys_basic(net, skb, flow, data, proto,
+ nhoff, hlen, flags, NULL,
+ false);
}
void skb_flow_dissect_meta(const struct sk_buff *skb,
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 418b9b813d65..0524dec15c6d 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -6017,6 +6017,7 @@ struct bpf_flow_keys {
};
__u32 flags;
__be32 flow_label;
+ __bpf_md_ptr(const struct virtio_net_hdr *, vhdr);
};
struct bpf_func_info {
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 331b170d9fcc..d4876d5e8959 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -3372,18 +3372,6 @@ static int check_ctx_access(struct bpf_verifier_env *env, int insn_idx, int off,
return -EACCES;
}
-static int check_flow_keys_access(struct bpf_verifier_env *env, int off,
- int size)
-{
- if (size < 0 || off < 0 ||
- (u64)off + size > sizeof(struct bpf_flow_keys)) {
- verbose(env, "invalid access to flow keys off=%d size=%d\n",
- off, size);
- return -EACCES;
- }
- return 0;
-}
-
static int check_sock_access(struct bpf_verifier_env *env, int insn_idx,
u32 regno, int off, int size,
enum bpf_access_type t)
@@ -4210,6 +4198,8 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn
if (!err && t == BPF_READ && value_regno >= 0)
mark_reg_unknown(env, regs, value_regno);
} else if (reg->type == PTR_TO_FLOW_KEYS) {
+ struct bpf_insn_access_aux info = {};
+
if (t == BPF_WRITE && value_regno >= 0 &&
is_pointer_value(env, value_regno)) {
verbose(env, "R%d leaks addr into flow keys\n",
@@ -4217,9 +4207,22 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn
return -EACCES;
}
- err = check_flow_keys_access(env, off, size);
- if (!err && t == BPF_READ && value_regno >= 0)
- mark_reg_unknown(env, regs, value_regno);
+ err = bpf_flow_keys_is_valid_access(off, size, t, &info);
+ if (err) {
+ verbose(env,
+ "invalid access to flow keys off=%d size=%d\n",
+ off, size);
+ } else if (t == BPF_READ && value_regno >= 0) {
+ if (info.reg_type == PTR_TO_BTF_ID_OR_NULL) {
+ mark_reg_known_zero(env, regs, value_regno);
+ regs[value_regno].type = info.reg_type;
+ regs[value_regno].btf = info.btf;
+ regs[value_regno].btf_id = info.btf_id;
+ regs[value_regno].id = ++env->id_gen;
+ } else {
+ mark_reg_unknown(env, regs, value_regno);
+ }
+ }
} else if (type_is_sk_pointer(reg->type)) {
if (t == BPF_WRITE) {
verbose(env, "R%d cannot write into %s\n",
diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
index aa47af349ba8..a11c5ce99ccb 100644
--- a/net/bpf/test_run.c
+++ b/net/bpf/test_run.c
@@ -797,7 +797,7 @@ int bpf_prog_test_run_flow_dissector(struct bpf_prog *prog,
bpf_test_timer_enter(&t);
do {
retval = bpf_flow_dissect(prog, &ctx, eth->h_proto, ETH_HLEN,
- size, flags);
+ size, flags, NULL, false);
} while (bpf_test_timer_continue(&t, repeat, &ret, &duration));
bpf_test_timer_leave(&t);
diff --git a/net/core/filter.c b/net/core/filter.c
index 239de1306de9..c3964ef8f387 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -7880,6 +7880,33 @@ static bool sock_filter_is_valid_access(int off, int size,
prog->expected_attach_type);
}
+BTF_ID_LIST_SINGLE(bpf_flow_dissector_btf_ids, struct, virtio_net_hdr);
+
+int bpf_flow_keys_is_valid_access(int off, int size, enum bpf_access_type t,
+ struct bpf_insn_access_aux *info)
+{
+ if (off < 0 ||
+ (u64)off + size > offsetofend(struct bpf_flow_keys, vhdr))
+ return -EACCES;
+
+ switch (off) {
+ case bpf_ctx_range_ptr(struct bpf_flow_keys, vhdr):
+ if (t == BPF_WRITE || off % size != 0 || size != sizeof(__u64))
+ return -EACCES;
+
+ if (!bpf_flow_dissector_btf_ids[0])
+ return -EINVAL;
+
+ info->btf = bpf_get_btf_vmlinux();
+ info->reg_type = PTR_TO_BTF_ID_OR_NULL;
+ info->btf_id = bpf_flow_dissector_btf_ids[0];
+
+ break;
+ }
+
+ return 0;
+}
+
static int bpf_noop_prologue(struct bpf_insn *insn_buf, bool direct_write,
const struct bpf_prog *prog)
{
@@ -8358,6 +8385,8 @@ static bool flow_dissector_is_valid_access(int off, int size,
return false;
info->reg_type = PTR_TO_FLOW_KEYS;
return true;
+ case bpf_ctx_range(struct __sk_buff, len):
+ return size == size_default;
default:
return false;
}
@@ -8390,6 +8419,30 @@ static u32 flow_dissector_convert_ctx_access(enum bpf_access_type type,
si->dst_reg, si->src_reg,
offsetof(struct bpf_flow_dissector, flow_keys));
break;
+
+ case offsetof(struct __sk_buff, len):
+ *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct bpf_flow_dissector, skb),
+ si->dst_reg, si->src_reg,
+ offsetof(struct bpf_flow_dissector, skb));
+ *insn++ = BPF_JMP_IMM(BPF_JNE, si->dst_reg, 0, 4);
+ /* bpf_flow_dissector->skb == NULL */
+ /* dst_reg = bpf_flow_dissector->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));
+ /* AX = bpf_flow_dissector->data */
+ *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct bpf_flow_dissector, data),
+ BPF_REG_AX, si->src_reg,
+ offsetof(struct bpf_flow_dissector, data));
+ /* dst_reg -= bpf_flow_dissector->data */
+ *insn++ = BPF_ALU64_REG(BPF_SUB, si->dst_reg, BPF_REG_AX);
+ *insn++ = BPF_JMP_A(1);
+ /* bpf_flow_dissector->skb != NULL */
+ /* bpf_flow_dissector->skb->len */
+ *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct sk_buff, len),
+ si->dst_reg, si->dst_reg,
+ offsetof(struct sk_buff, len));
+ break;
}
return insn - insn_buf;
diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index 2aadbfc5193b..609e24ba98ea 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -28,6 +28,7 @@
#include <scsi/fc/fc_fcoe.h>
#include <uapi/linux/batadv_packet.h>
#include <linux/bpf.h>
+#include <linux/virtio_net.h>
#if IS_ENABLED(CONFIG_NF_CONNTRACK)
#include <net/netfilter/nf_conntrack_core.h>
#include <net/netfilter/nf_conntrack_labels.h>
@@ -864,16 +865,38 @@ static void __skb_flow_bpf_to_target(const struct bpf_flow_keys *flow_keys,
}
bool bpf_flow_dissect(struct bpf_prog *prog, struct bpf_flow_dissector *ctx,
- __be16 proto, int nhoff, int hlen, unsigned int flags)
+ __be16 proto, int nhoff, int hlen, unsigned int flags,
+ const struct virtio_net_hdr *vhdr,
+ bool vhdr_is_little_endian)
{
struct bpf_flow_keys *flow_keys = ctx->flow_keys;
u32 result;
+/* vnet hdr is either machine endian (virtio spec < v1) or le (>= v1) */
+#if defined(__BIG_ENDIAN_BITFIELD)
+ struct virtio_net_hdr vnet_hdr_local;
+
+ if (vhdr && vhdr_is_little_endian) {
+ vnet_hdr_local.flags = vhdr->flags;
+ vnet_hdr_local.gso_type = vhdr->gso_type;
+ vnet_hdr_local.hdr_len = __virtio16_to_cpu(false,
+ vhdr->hdr_len);
+ vnet_hdr_local.gso_size = __virtio16_to_cpu(false,
+ vhdr->gso_size);
+ vnet_hdr_local.csum_start = __virtio16_to_cpu(false,
+ vhdr->csum_start);
+ vnet_hdr_local.csum_offset = __virtio16_to_cpu(false,
+ vhdr->csum_offset);
+ vhdr = &vnet_hdr_local;
+ }
+#endif
+
/* Pass parameters to the BPF program */
memset(flow_keys, 0, sizeof(*flow_keys));
flow_keys->n_proto = proto;
flow_keys->nhoff = nhoff;
flow_keys->thoff = flow_keys->nhoff;
+ flow_keys->vhdr = vhdr;
BUILD_BUG_ON((int)BPF_FLOW_DISSECTOR_F_PARSE_1ST_FRAG !=
(int)FLOW_DISSECTOR_F_PARSE_1ST_FRAG);
@@ -904,6 +927,8 @@ bool bpf_flow_dissect(struct bpf_prog *prog, struct bpf_flow_dissector *ctx,
* @hlen: packet header length, if @data is NULL use skb_headlen(skb)
* @flags: flags that control the dissection process, e.g.
* FLOW_DISSECTOR_F_STOP_AT_ENCAP.
+ * @vhdr: virtio_net_header to include in kernel context for BPF flow dissector
+ * @vhdr_is_little_endian: whether virtio_net_hdr fields are little endian
*
* The function will try to retrieve individual keys into target specified
* by flow_dissector from either the skbuff or a raw buffer specified by the
@@ -915,7 +940,9 @@ bool __skb_flow_dissect(const struct net *net,
const struct sk_buff *skb,
struct flow_dissector *flow_dissector,
void *target_container, const void *data,
- __be16 proto, int nhoff, int hlen, unsigned int flags)
+ __be16 proto, int nhoff, int hlen, unsigned int flags,
+ const struct virtio_net_hdr *vhdr,
+ bool vhdr_is_little_endian)
{
struct flow_dissector_key_control *key_control;
struct flow_dissector_key_basic *key_basic;
@@ -1012,7 +1039,8 @@ bool __skb_flow_dissect(const struct net *net,
prog = READ_ONCE(run_array->items[0].prog);
ret = bpf_flow_dissect(prog, &ctx, n_proto, nhoff,
- hlen, flags);
+ hlen, flags, vhdr,
+ vhdr_is_little_endian);
__skb_flow_bpf_to_target(&flow_keys, flow_dissector,
target_container);
rcu_read_unlock();
@@ -1610,7 +1638,7 @@ u32 __skb_get_hash_symmetric(const struct sk_buff *skb)
memset(&keys, 0, sizeof(keys));
__skb_flow_dissect(NULL, skb, &flow_keys_dissector_symmetric,
&keys, NULL, 0, 0, 0,
- FLOW_DISSECTOR_F_STOP_AT_FLOW_LABEL);
+ FLOW_DISSECTOR_F_STOP_AT_FLOW_LABEL, NULL, false);
return __flow_hash_from_keys(&keys, &hashrnd);
}
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 418b9b813d65..0524dec15c6d 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -6017,6 +6017,7 @@ struct bpf_flow_keys {
};
__u32 flags;
__be32 flow_label;
+ __bpf_md_ptr(const struct virtio_net_hdr *, vhdr);
};
struct bpf_func_info {
--
2.32.0.272.g935e593368-goog
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