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Date: Thu, 4 Jun 2015 10:11:54 -0700
From: Alexei Starovoitov <ast@...mgrid.com>
To: "David S. Miller" <davem@...emloft.net>
Cc: Eric Dumazet <edumazet@...gle.com>,
Jamal Hadi Salim <jhs@...atatu.com>,
Daniel Borkmann <daniel@...earbox.net>, netdev@...r.kernel.org
Subject: [PATCH v2 net-next 2/2] bpf: allow programs to write to certain skb fields
allow programs read/write skb->mark, tc_index fields and
((struct qdisc_skb_cb *)cb)->data.
mark and tc_index are generically useful in TC.
cb[0]-cb[4] are primarily used to pass arguments from one
program to another called via bpf_tail_call() which can
be seen in sockex3_kern.c example.
All fields of 'struct __sk_buff' are readable to socket and tc_cls_act progs.
mark, tc_index are writeable from tc_cls_act only.
cb[0]-cb[4] are writeable by both sockets and tc_cls_act.
Add verifier tests and improve sample code.
Signed-off-by: Alexei Starovoitov <ast@...mgrid.com>
---
v1->v2: no changes
This patch is independent from previous push/pull l2 patch, but
they both modify net/core/filter.c, so sent together.
include/linux/bpf.h | 3 +-
include/uapi/linux/bpf.h | 2 +
kernel/bpf/verifier.c | 37 ++++++++++++-----
net/core/filter.c | 94 +++++++++++++++++++++++++++++++++++++------
samples/bpf/sockex3_kern.c | 35 +++++-----------
samples/bpf/test_verifier.c | 84 +++++++++++++++++++++++++++++++++++++-
6 files changed, 207 insertions(+), 48 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index ca854e5bb2f7..2235aee8096a 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -105,7 +105,8 @@ struct bpf_verifier_ops {
*/
bool (*is_valid_access)(int off, int size, enum bpf_access_type type);
- u32 (*convert_ctx_access)(int dst_reg, int src_reg, int ctx_off,
+ u32 (*convert_ctx_access)(enum bpf_access_type type, int dst_reg,
+ int src_reg, int ctx_off,
struct bpf_insn *insn);
};
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 42aa19abab86..602f05b7a275 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -248,6 +248,8 @@ struct __sk_buff {
__u32 priority;
__u32 ingress_ifindex;
__u32 ifindex;
+ __u32 tc_index;
+ __u32 cb[5];
};
#endif /* _UAPI__LINUX_BPF_H__ */
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index cfd9a40b9a5a..039d866fd36a 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1692,6 +1692,8 @@ static int do_check(struct verifier_env *env)
}
} else if (class == BPF_STX) {
+ enum bpf_reg_type dst_reg_type;
+
if (BPF_MODE(insn->code) == BPF_XADD) {
err = check_xadd(env, insn);
if (err)
@@ -1700,11 +1702,6 @@ static int do_check(struct verifier_env *env)
continue;
}
- if (BPF_MODE(insn->code) != BPF_MEM ||
- insn->imm != 0) {
- verbose("BPF_STX uses reserved fields\n");
- return -EINVAL;
- }
/* check src1 operand */
err = check_reg_arg(regs, insn->src_reg, SRC_OP);
if (err)
@@ -1714,6 +1711,8 @@ static int do_check(struct verifier_env *env)
if (err)
return err;
+ dst_reg_type = regs[insn->dst_reg].type;
+
/* check that memory (dst_reg + off) is writeable */
err = check_mem_access(env, insn->dst_reg, insn->off,
BPF_SIZE(insn->code), BPF_WRITE,
@@ -1721,6 +1720,15 @@ static int do_check(struct verifier_env *env)
if (err)
return err;
+ if (insn->imm == 0) {
+ insn->imm = dst_reg_type;
+ } else if (dst_reg_type != insn->imm &&
+ (dst_reg_type == PTR_TO_CTX ||
+ insn->imm == PTR_TO_CTX)) {
+ verbose("same insn cannot be used with different pointers\n");
+ return -EINVAL;
+ }
+
} else if (class == BPF_ST) {
if (BPF_MODE(insn->code) != BPF_MEM ||
insn->src_reg != BPF_REG_0) {
@@ -1839,12 +1847,18 @@ static int replace_map_fd_with_map_ptr(struct verifier_env *env)
for (i = 0; i < insn_cnt; i++, insn++) {
if (BPF_CLASS(insn->code) == BPF_LDX &&
- (BPF_MODE(insn->code) != BPF_MEM ||
- insn->imm != 0)) {
+ (BPF_MODE(insn->code) != BPF_MEM || insn->imm != 0)) {
verbose("BPF_LDX uses reserved fields\n");
return -EINVAL;
}
+ if (BPF_CLASS(insn->code) == BPF_STX &&
+ ((BPF_MODE(insn->code) != BPF_MEM &&
+ BPF_MODE(insn->code) != BPF_XADD) || insn->imm != 0)) {
+ verbose("BPF_STX uses reserved fields\n");
+ return -EINVAL;
+ }
+
if (insn[0].code == (BPF_LD | BPF_IMM | BPF_DW)) {
struct bpf_map *map;
struct fd f;
@@ -1967,12 +1981,17 @@ static int convert_ctx_accesses(struct verifier_env *env)
struct bpf_prog *new_prog;
u32 cnt;
int i;
+ enum bpf_access_type type;
if (!env->prog->aux->ops->convert_ctx_access)
return 0;
for (i = 0; i < insn_cnt; i++, insn++) {
- if (insn->code != (BPF_LDX | BPF_MEM | BPF_W))
+ if (insn->code == (BPF_LDX | BPF_MEM | BPF_W))
+ type = BPF_READ;
+ else if (insn->code == (BPF_STX | BPF_MEM | BPF_W))
+ type = BPF_WRITE;
+ else
continue;
if (insn->imm != PTR_TO_CTX) {
@@ -1982,7 +2001,7 @@ static int convert_ctx_accesses(struct verifier_env *env)
}
cnt = env->prog->aux->ops->
- convert_ctx_access(insn->dst_reg, insn->src_reg,
+ convert_ctx_access(type, insn->dst_reg, insn->src_reg,
insn->off, insn_buf);
if (cnt == 0 || cnt >= ARRAY_SIZE(insn_buf)) {
verbose("bpf verifier is misconfigured\n");
diff --git a/net/core/filter.c b/net/core/filter.c
index 36a69e33d76b..d271c06bf01f 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -46,6 +46,7 @@
#include <linux/seccomp.h>
#include <linux/if_vlan.h>
#include <linux/bpf.h>
+#include <net/sch_generic.h>
/**
* sk_filter - run a packet through a socket filter
@@ -1463,13 +1464,8 @@ tc_cls_act_func_proto(enum bpf_func_id func_id)
}
}
-static bool sk_filter_is_valid_access(int off, int size,
- enum bpf_access_type type)
+static bool __is_valid_access(int off, int size, enum bpf_access_type type)
{
- /* only read is allowed */
- if (type != BPF_READ)
- return false;
-
/* check bounds */
if (off < 0 || off >= sizeof(struct __sk_buff))
return false;
@@ -1485,8 +1481,42 @@ static bool sk_filter_is_valid_access(int off, int size,
return true;
}
-static u32 sk_filter_convert_ctx_access(int dst_reg, int src_reg, int ctx_off,
- struct bpf_insn *insn_buf)
+static bool sk_filter_is_valid_access(int off, int size,
+ enum bpf_access_type type)
+{
+ if (type == BPF_WRITE) {
+ switch (off) {
+ case offsetof(struct __sk_buff, cb[0]) ...
+ offsetof(struct __sk_buff, cb[4]):
+ break;
+ default:
+ return false;
+ }
+ }
+
+ return __is_valid_access(off, size, type);
+}
+
+static bool tc_cls_act_is_valid_access(int off, int size,
+ enum bpf_access_type type)
+{
+ if (type == BPF_WRITE) {
+ switch (off) {
+ case offsetof(struct __sk_buff, mark):
+ case offsetof(struct __sk_buff, tc_index):
+ case offsetof(struct __sk_buff, cb[0]) ...
+ offsetof(struct __sk_buff, cb[4]):
+ break;
+ default:
+ return false;
+ }
+ }
+ return __is_valid_access(off, size, type);
+}
+
+static u32 bpf_net_convert_ctx_access(enum bpf_access_type type, int dst_reg,
+ int src_reg, int ctx_off,
+ struct bpf_insn *insn_buf)
{
struct bpf_insn *insn = insn_buf;
@@ -1538,7 +1568,15 @@ static u32 sk_filter_convert_ctx_access(int dst_reg, int src_reg, int ctx_off,
break;
case offsetof(struct __sk_buff, mark):
- return convert_skb_access(SKF_AD_MARK, dst_reg, src_reg, insn);
+ BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, mark) != 4);
+
+ if (type == BPF_WRITE)
+ *insn++ = BPF_STX_MEM(BPF_W, dst_reg, src_reg,
+ offsetof(struct sk_buff, mark));
+ else
+ *insn++ = BPF_LDX_MEM(BPF_W, dst_reg, src_reg,
+ offsetof(struct sk_buff, mark));
+ break;
case offsetof(struct __sk_buff, pkt_type):
return convert_skb_access(SKF_AD_PKTTYPE, dst_reg, src_reg, insn);
@@ -1553,6 +1591,38 @@ static u32 sk_filter_convert_ctx_access(int dst_reg, int src_reg, int ctx_off,
case offsetof(struct __sk_buff, vlan_tci):
return convert_skb_access(SKF_AD_VLAN_TAG,
dst_reg, src_reg, insn);
+
+ case offsetof(struct __sk_buff, cb[0]) ...
+ offsetof(struct __sk_buff, cb[4]):
+ BUILD_BUG_ON(FIELD_SIZEOF(struct qdisc_skb_cb, data) < 20);
+
+ ctx_off -= offsetof(struct __sk_buff, cb[0]);
+ ctx_off += offsetof(struct sk_buff, cb);
+ ctx_off += offsetof(struct qdisc_skb_cb, data);
+ if (type == BPF_WRITE)
+ *insn++ = BPF_STX_MEM(BPF_W, dst_reg, src_reg, ctx_off);
+ else
+ *insn++ = BPF_LDX_MEM(BPF_W, dst_reg, src_reg, ctx_off);
+ break;
+
+ case offsetof(struct __sk_buff, tc_index):
+#ifdef CONFIG_NET_SCHED
+ BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, tc_index) != 2);
+
+ if (type == BPF_WRITE)
+ *insn++ = BPF_STX_MEM(BPF_H, dst_reg, src_reg,
+ offsetof(struct sk_buff, tc_index));
+ else
+ *insn++ = BPF_LDX_MEM(BPF_H, dst_reg, src_reg,
+ offsetof(struct sk_buff, tc_index));
+ break;
+#else
+ if (type == BPF_WRITE)
+ *insn++ = BPF_MOV64_REG(dst_reg, dst_reg);
+ else
+ *insn++ = BPF_MOV64_IMM(dst_reg, 0);
+ break;
+#endif
}
return insn - insn_buf;
@@ -1561,13 +1631,13 @@ static u32 sk_filter_convert_ctx_access(int dst_reg, int src_reg, int ctx_off,
static const struct bpf_verifier_ops sk_filter_ops = {
.get_func_proto = sk_filter_func_proto,
.is_valid_access = sk_filter_is_valid_access,
- .convert_ctx_access = sk_filter_convert_ctx_access,
+ .convert_ctx_access = bpf_net_convert_ctx_access,
};
static const struct bpf_verifier_ops tc_cls_act_ops = {
.get_func_proto = tc_cls_act_func_proto,
- .is_valid_access = sk_filter_is_valid_access,
- .convert_ctx_access = sk_filter_convert_ctx_access,
+ .is_valid_access = tc_cls_act_is_valid_access,
+ .convert_ctx_access = bpf_net_convert_ctx_access,
};
static struct bpf_prog_type_list sk_filter_type __read_mostly = {
diff --git a/samples/bpf/sockex3_kern.c b/samples/bpf/sockex3_kern.c
index 2625b987944f..41ae2fd21b13 100644
--- a/samples/bpf/sockex3_kern.c
+++ b/samples/bpf/sockex3_kern.c
@@ -89,7 +89,6 @@ static inline __u32 ipv6_addr_hash(struct __sk_buff *ctx, __u64 off)
struct globals {
struct flow_keys flow;
- __u32 nhoff;
};
struct bpf_map_def SEC("maps") percpu_map = {
@@ -139,7 +138,7 @@ static void update_stats(struct __sk_buff *skb, struct globals *g)
static __always_inline void parse_ip_proto(struct __sk_buff *skb,
struct globals *g, __u32 ip_proto)
{
- __u32 nhoff = g->nhoff;
+ __u32 nhoff = skb->cb[0];
int poff;
switch (ip_proto) {
@@ -165,7 +164,7 @@ static __always_inline void parse_ip_proto(struct __sk_buff *skb,
if (gre_flags & GRE_SEQ)
nhoff += 4;
- g->nhoff = nhoff;
+ skb->cb[0] = nhoff;
parse_eth_proto(skb, gre_proto);
break;
}
@@ -195,7 +194,7 @@ PROG(PARSE_IP)(struct __sk_buff *skb)
if (!g)
return 0;
- nhoff = g->nhoff;
+ nhoff = skb->cb[0];
if (unlikely(ip_is_fragment(skb, nhoff)))
return 0;
@@ -210,7 +209,7 @@ PROG(PARSE_IP)(struct __sk_buff *skb)
verlen = load_byte(skb, nhoff + 0/*offsetof(struct iphdr, ihl)*/);
nhoff += (verlen & 0xF) << 2;
- g->nhoff = nhoff;
+ skb->cb[0] = nhoff;
parse_ip_proto(skb, g, ip_proto);
return 0;
}
@@ -223,7 +222,7 @@ PROG(PARSE_IPV6)(struct __sk_buff *skb)
if (!g)
return 0;
- nhoff = g->nhoff;
+ nhoff = skb->cb[0];
ip_proto = load_byte(skb,
nhoff + offsetof(struct ipv6hdr, nexthdr));
@@ -233,25 +232,21 @@ PROG(PARSE_IPV6)(struct __sk_buff *skb)
nhoff + offsetof(struct ipv6hdr, daddr));
nhoff += sizeof(struct ipv6hdr);
- g->nhoff = nhoff;
+ skb->cb[0] = nhoff;
parse_ip_proto(skb, g, ip_proto);
return 0;
}
PROG(PARSE_VLAN)(struct __sk_buff *skb)
{
- struct globals *g = this_cpu_globals();
__u32 nhoff, proto;
- if (!g)
- return 0;
-
- nhoff = g->nhoff;
+ nhoff = skb->cb[0];
proto = load_half(skb, nhoff + offsetof(struct vlan_hdr,
h_vlan_encapsulated_proto));
nhoff += sizeof(struct vlan_hdr);
- g->nhoff = nhoff;
+ skb->cb[0] = nhoff;
parse_eth_proto(skb, proto);
@@ -260,17 +255,13 @@ PROG(PARSE_VLAN)(struct __sk_buff *skb)
PROG(PARSE_MPLS)(struct __sk_buff *skb)
{
- struct globals *g = this_cpu_globals();
__u32 nhoff, label;
- if (!g)
- return 0;
-
- nhoff = g->nhoff;
+ nhoff = skb->cb[0];
label = load_word(skb, nhoff);
nhoff += sizeof(struct mpls_label);
- g->nhoff = nhoff;
+ skb->cb[0] = nhoff;
if (label & MPLS_LS_S_MASK) {
__u8 verlen = load_byte(skb, nhoff);
@@ -288,14 +279,10 @@ PROG(PARSE_MPLS)(struct __sk_buff *skb)
SEC("socket/0")
int main_prog(struct __sk_buff *skb)
{
- struct globals *g = this_cpu_globals();
__u32 nhoff = ETH_HLEN;
__u32 proto = load_half(skb, 12);
- if (!g)
- return 0;
-
- g->nhoff = nhoff;
+ skb->cb[0] = nhoff;
parse_eth_proto(skb, proto);
return 0;
}
diff --git a/samples/bpf/test_verifier.c b/samples/bpf/test_verifier.c
index 12f3780af73f..693605997abc 100644
--- a/samples/bpf/test_verifier.c
+++ b/samples/bpf/test_verifier.c
@@ -29,6 +29,7 @@ struct bpf_test {
ACCEPT,
REJECT
} result;
+ enum bpf_prog_type prog_type;
};
static struct bpf_test tests[] = {
@@ -743,6 +744,84 @@ static struct bpf_test tests[] = {
.errstr = "different pointers",
.result = REJECT,
},
+ {
+ "check skb->mark is not writeable by sockets",
+ .insns = {
+ BPF_STX_MEM(BPF_W, BPF_REG_1, BPF_REG_1,
+ offsetof(struct __sk_buff, mark)),
+ BPF_EXIT_INSN(),
+ },
+ .errstr = "invalid bpf_context access",
+ .result = REJECT,
+ },
+ {
+ "check skb->tc_index is not writeable by sockets",
+ .insns = {
+ BPF_STX_MEM(BPF_W, BPF_REG_1, BPF_REG_1,
+ offsetof(struct __sk_buff, tc_index)),
+ BPF_EXIT_INSN(),
+ },
+ .errstr = "invalid bpf_context access",
+ .result = REJECT,
+ },
+ {
+ "check non-u32 access to cb",
+ .insns = {
+ BPF_STX_MEM(BPF_H, BPF_REG_1, BPF_REG_1,
+ offsetof(struct __sk_buff, cb[0])),
+ BPF_EXIT_INSN(),
+ },
+ .errstr = "invalid bpf_context access",
+ .result = REJECT,
+ },
+ {
+ "check out of range skb->cb access",
+ .insns = {
+ BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_1,
+ offsetof(struct __sk_buff, cb[60])),
+ BPF_EXIT_INSN(),
+ },
+ .errstr = "invalid bpf_context access",
+ .result = REJECT,
+ .prog_type = BPF_PROG_TYPE_SCHED_ACT,
+ },
+ {
+ "write skb fields from socket prog",
+ .insns = {
+ BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_1,
+ offsetof(struct __sk_buff, cb[4])),
+ BPF_JMP_IMM(BPF_JGE, BPF_REG_0, 0, 1),
+ BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_1,
+ offsetof(struct __sk_buff, mark)),
+ BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_1,
+ offsetof(struct __sk_buff, tc_index)),
+ BPF_JMP_IMM(BPF_JGE, BPF_REG_0, 0, 1),
+ BPF_STX_MEM(BPF_W, BPF_REG_1, BPF_REG_1,
+ offsetof(struct __sk_buff, cb[0])),
+ BPF_STX_MEM(BPF_W, BPF_REG_1, BPF_REG_1,
+ offsetof(struct __sk_buff, cb[2])),
+ BPF_EXIT_INSN(),
+ },
+ .result = ACCEPT,
+ },
+ {
+ "write skb fields from tc_cls_act prog",
+ .insns = {
+ BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_1,
+ offsetof(struct __sk_buff, cb[0])),
+ BPF_STX_MEM(BPF_W, BPF_REG_1, BPF_REG_0,
+ offsetof(struct __sk_buff, mark)),
+ BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_1,
+ offsetof(struct __sk_buff, tc_index)),
+ BPF_STX_MEM(BPF_W, BPF_REG_1, BPF_REG_0,
+ offsetof(struct __sk_buff, tc_index)),
+ BPF_STX_MEM(BPF_W, BPF_REG_1, BPF_REG_0,
+ offsetof(struct __sk_buff, cb[3])),
+ BPF_EXIT_INSN(),
+ },
+ .result = ACCEPT,
+ .prog_type = BPF_PROG_TYPE_SCHED_CLS,
+ },
};
static int probe_filter_length(struct bpf_insn *fp)
@@ -775,6 +854,7 @@ static int test(void)
for (i = 0; i < ARRAY_SIZE(tests); i++) {
struct bpf_insn *prog = tests[i].insns;
+ int prog_type = tests[i].prog_type;
int prog_len = probe_filter_length(prog);
int *fixup = tests[i].fixup;
int map_fd = -1;
@@ -789,8 +869,8 @@ static int test(void)
}
printf("#%d %s ", i, tests[i].descr);
- prog_fd = bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER, prog,
- prog_len * sizeof(struct bpf_insn),
+ prog_fd = bpf_prog_load(prog_type ?: BPF_PROG_TYPE_SOCKET_FILTER,
+ prog, prog_len * sizeof(struct bpf_insn),
"GPL", 0);
if (tests[i].result == ACCEPT) {
--
1.7.9.5
--
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