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authorAlexei Starovoitov <ast@plumgrid.com>2015-06-04 10:11:54 -0700
committerDavid S. Miller <davem@davemloft.net>2015-06-07 02:01:33 -0700
commitd691f9e8d4405c334aa10d556e73c8bf44cb0e01 (patch)
tree295b1d647364407c42990d916358a72381f4d534 /net
parent3431205e03977aaf32bce6d4b16fb8244b510056 (diff)
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@plumgrid.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
-rw-r--r--net/core/filter.c94
1 files changed, 82 insertions, 12 deletions
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 = {

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