From: Andrey Ignatov <r...@fb.com>
"Post-hooks" are hooks that are called right before returning from
sys_bind. At this time IP and port are already allocated and no further
changes to `struct sock` can happen before returning from sys_bind but
BPF program has a chance to inspect the socket and change sys_bind
result.
Specifically it can e.g. inspect what port was allocated and if it
doesn't satisfy some policy, BPF program can force sys_bind to fail and
return EPERM to user.
Another example of usage is recording the IP:port pair to some map to
use it in later calls to sys_connect. E.g. if some TCP server inside
cgroup was bound to some IP:port_n, it can be recorded to a map. And
later when some TCP client inside same cgroup is trying to connect to
127.0.0.1:port_n, BPF hook for sys_connect can override the destination
and connect application to IP:port_n instead of 127.0.0.1:port_n. That
helps forcing all applications inside a cgroup to use desired IP and not
break those applications if they e.g. use localhost to communicate
between each other.
== Implementation details ==
Post-hooks are implemented as two new attach types
`BPF_CGROUP_INET4_POST_BIND` and `BPF_CGROUP_INET6_POST_BIND` for
existing prog type `BPF_PROG_TYPE_CGROUP_SOCK`.
Separate attach types for IPv4 and IPv6 are introduced to avoid access
to IPv6 field in `struct sock` from `inet_bind()` and to IPv4 field from
`inet6_bind()` since those fields might not make sense in such cases.
Signed-off-by: Andrey Ignatov <r...@fb.com>
Signed-off-by: Alexei Starovoitov <a...@kernel.org>
---
include/linux/bpf-cgroup.h | 16 +++++--
include/uapi/linux/bpf.h | 11 +++++
kernel/bpf/syscall.c | 43 +++++++++++++++++
net/core/filter.c | 116 +++++++++++++++++++++++++++++++++++++++------
net/ipv4/af_inet.c | 18 ++++---
net/ipv6/af_inet6.c | 21 +++++---
6 files changed, 195 insertions(+), 30 deletions(-)
diff --git a/include/linux/bpf-cgroup.h b/include/linux/bpf-cgroup.h
index c6ab295e6dcb..30d15e64b993 100644
--- a/include/linux/bpf-cgroup.h
+++ b/include/linux/bpf-cgroup.h
@@ -98,16 +98,24 @@ int __cgroup_bpf_check_dev_permission(short dev_type, u32
major, u32 minor,
__ret; \
})
-#define BPF_CGROUP_RUN_PROG_INET_SOCK(sk) \
+#define BPF_CGROUP_RUN_SK_PROG(sk, type) \
({ \
int __ret = 0; \
if (cgroup_bpf_enabled) { \
- __ret = __cgroup_bpf_run_filter_sk(sk, \
- BPF_CGROUP_INET_SOCK_CREATE); \
+ __ret = __cgroup_bpf_run_filter_sk(sk, type); \
} \
__ret; \
})
+#define BPF_CGROUP_RUN_PROG_INET_SOCK(sk) \
+ BPF_CGROUP_RUN_SK_PROG(sk, BPF_CGROUP_INET_SOCK_CREATE)
+
+#define BPF_CGROUP_RUN_PROG_INET4_POST_BIND(sk)
\
+ BPF_CGROUP_RUN_SK_PROG(sk, BPF_CGROUP_INET4_POST_BIND)
+
+#define BPF_CGROUP_RUN_PROG_INET6_POST_BIND(sk)
\
+ BPF_CGROUP_RUN_SK_PROG(sk, BPF_CGROUP_INET6_POST_BIND)
+
#define BPF_CGROUP_RUN_SA_PROG(sk, uaddr, type)
\
({ \
int __ret = 0; \
@@ -183,6 +191,8 @@ static inline int cgroup_bpf_inherit(struct cgroup *cgrp) {
return 0; }
#define BPF_CGROUP_RUN_PROG_INET_SOCK(sk) ({ 0; })
#define BPF_CGROUP_RUN_PROG_INET4_BIND(sk, uaddr) ({ 0; })
#define BPF_CGROUP_RUN_PROG_INET6_BIND(sk, uaddr) ({ 0; })
+#define BPF_CGROUP_RUN_PROG_INET4_POST_BIND(sk) ({ 0; })
+#define BPF_CGROUP_RUN_PROG_INET6_POST_BIND(sk) ({ 0; })
#define BPF_CGROUP_RUN_PROG_INET4_CONNECT(sk, uaddr) ({ 0; })
#define BPF_CGROUP_RUN_PROG_INET4_CONNECT_LOCK(sk, uaddr) ({ 0; })
#define BPF_CGROUP_RUN_PROG_INET6_CONNECT(sk, uaddr) ({ 0; })
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 77afaf1ba556..c5ec89732a8d 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -152,6 +152,8 @@ enum bpf_attach_type {
BPF_CGROUP_INET6_BIND,
BPF_CGROUP_INET4_CONNECT,
BPF_CGROUP_INET6_CONNECT,
+ BPF_CGROUP_INET4_POST_BIND,
+ BPF_CGROUP_INET6_POST_BIND,
__MAX_BPF_ATTACH_TYPE
};
@@ -948,6 +950,15 @@ struct bpf_sock {
__u32 protocol;
__u32 mark;
__u32 priority;
+ __u32 src_ip4; /* Allows 1,2,4-byte read.
+ * Stored in network byte order.
+ */
+ __u32 src_ip6[4]; /* Allows 1,2,4-byte read.
+ * Stored in network byte order.
+ */
+ __u32 src_port; /* Allows 4-byte read.
+ * Stored in host byte order
+ */
};
#define XDP_PACKET_HEADROOM 256
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index cf1b29bc0ab8..0244973ee544 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1171,11 +1171,46 @@ struct bpf_prog *bpf_prog_get_type_dev(u32 ufd, enum
bpf_prog_type type,
}
EXPORT_SYMBOL_GPL(bpf_prog_get_type_dev);
+/* Initially all BPF programs could be loaded w/o specifying
+ * expected_attach_type. Later for some of them specifying expected_attach_type
+ * at load time became required so that program could be validated properly.
+ * Programs of types that are allowed to be loaded both w/ and w/o (for
+ * backward compatibility) expected_attach_type, should have the default attach
+ * type assigned to expected_attach_type for the latter case, so that it can be
+ * validated later at attach time.
+ *
+ * bpf_prog_load_fixup_attach_type() sets expected_attach_type in @attr if
+ * prog type requires it but has some attach types that have to be backward
+ * compatible.
+ */
+static void bpf_prog_load_fixup_attach_type(union bpf_attr *attr)
+{
+ switch (attr->prog_type) {
+ case BPF_PROG_TYPE_CGROUP_SOCK:
+ /* Unfortunately BPF_ATTACH_TYPE_UNSPEC enumeration doesn't
+ * exist so checking for non-zero is the way to go here.
+ */
+ if (!attr->expected_attach_type)
+ attr->expected_attach_type =
+ BPF_CGROUP_INET_SOCK_CREATE;
+ break;
+ }
+}
+
static int
bpf_prog_load_check_attach_type(enum bpf_prog_type prog_type,
enum bpf_attach_type expected_attach_type)
{
switch (prog_type) {
+ case BPF_PROG_TYPE_CGROUP_SOCK:
+ switch (expected_attach_type) {
+ case BPF_CGROUP_INET_SOCK_CREATE:
+ case BPF_CGROUP_INET4_POST_BIND:
+ case BPF_CGROUP_INET6_POST_BIND:
+ return 0;
+ default:
+ return -EINVAL;
+ }
case BPF_PROG_TYPE_CGROUP_SOCK_ADDR:
switch (expected_attach_type) {
case BPF_CGROUP_INET4_BIND:
@@ -1195,6 +1230,7 @@ static int bpf_prog_attach_check_attach_type(const struct
bpf_prog *prog,
enum bpf_attach_type attach_type)
{
switch (prog->type) {
+ case BPF_PROG_TYPE_CGROUP_SOCK:
case BPF_PROG_TYPE_CGROUP_SOCK_ADDR:
return attach_type == prog->expected_attach_type ? 0 : -EINVAL;
default:
@@ -1240,6 +1276,7 @@ static int bpf_prog_load(union bpf_attr *attr)
!capable(CAP_SYS_ADMIN))
return -EPERM;
+ bpf_prog_load_fixup_attach_type(attr);
if (bpf_prog_load_check_attach_type(type, attr->expected_attach_type))
return -EINVAL;
@@ -1489,6 +1526,8 @@ static int bpf_prog_attach(const union bpf_attr *attr)
ptype = BPF_PROG_TYPE_CGROUP_SKB;
break;
case BPF_CGROUP_INET_SOCK_CREATE:
+ case BPF_CGROUP_INET4_POST_BIND:
+ case BPF_CGROUP_INET6_POST_BIND:
ptype = BPF_PROG_TYPE_CGROUP_SOCK;
break;
case BPF_CGROUP_INET4_BIND:
@@ -1557,6 +1596,8 @@ static int bpf_prog_detach(const union bpf_attr *attr)
ptype = BPF_PROG_TYPE_CGROUP_SKB;
break;
case BPF_CGROUP_INET_SOCK_CREATE:
+ case BPF_CGROUP_INET4_POST_BIND:
+ case BPF_CGROUP_INET6_POST_BIND:
ptype = BPF_PROG_TYPE_CGROUP_SOCK;
break;
case BPF_CGROUP_INET4_BIND:
@@ -1616,6 +1657,8 @@ static int bpf_prog_query(const union bpf_attr *attr,
case BPF_CGROUP_INET_SOCK_CREATE:
case BPF_CGROUP_INET4_BIND:
case BPF_CGROUP_INET6_BIND:
+ case BPF_CGROUP_INET4_POST_BIND:
+ case BPF_CGROUP_INET6_POST_BIND:
case BPF_CGROUP_INET4_CONNECT:
case BPF_CGROUP_INET6_CONNECT:
case BPF_CGROUP_SOCK_OPS:
diff --git a/net/core/filter.c b/net/core/filter.c
index bdb9cadd4d27..d31aff93270d 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -4097,30 +4097,80 @@ static bool lwt_is_valid_access(int off, int size,
return bpf_skb_is_valid_access(off, size, type, prog, info);
}
-static bool sock_filter_is_valid_access(int off, int size,
- enum bpf_access_type type,
- const struct bpf_prog *prog,
- struct bpf_insn_access_aux *info)
+
+/* Attach type specific accesses */
+static bool __sock_filter_check_attach_type(int off,
+ enum bpf_access_type access_type,
+ enum bpf_attach_type attach_type)
{
- if (type == BPF_WRITE) {
- switch (off) {
- case offsetof(struct bpf_sock, bound_dev_if):
- case offsetof(struct bpf_sock, mark):
- case offsetof(struct bpf_sock, priority):
- break;
+ switch (off) {
+ case offsetof(struct bpf_sock, bound_dev_if):
+ case offsetof(struct bpf_sock, mark):
+ case offsetof(struct bpf_sock, priority):
+ switch (attach_type) {
+ case BPF_CGROUP_INET_SOCK_CREATE:
+ goto full_access;
+ default:
+ return false;
+ }
+ case bpf_ctx_range(struct bpf_sock, src_ip4):
+ switch (attach_type) {
+ case BPF_CGROUP_INET4_POST_BIND:
+ goto read_only;
+ default:
+ return false;
+ }
+ case bpf_ctx_range_till(struct bpf_sock, src_ip6[0], src_ip6[3]):
+ switch (attach_type) {
+ case BPF_CGROUP_INET6_POST_BIND:
+ goto read_only;
+ default:
+ return false;
+ }
+ case bpf_ctx_range(struct bpf_sock, src_port):
+ switch (attach_type) {
+ case BPF_CGROUP_INET4_POST_BIND:
+ case BPF_CGROUP_INET6_POST_BIND:
+ goto read_only;
default:
return false;
}
}
+read_only:
+ return access_type == BPF_READ;
+full_access:
+ return true;
+}
+
+static bool __sock_filter_check_size(int off, int size,
+ struct bpf_insn_access_aux *info)
+{
+ const int size_default = sizeof(__u32);
- if (off < 0 || off + size > sizeof(struct bpf_sock))
+ switch (off) {
+ case bpf_ctx_range(struct bpf_sock, src_ip4):
+ case bpf_ctx_range_till(struct bpf_sock, src_ip6[0], src_ip6[3]):
+ bpf_ctx_record_field_size(info, size_default);
+ return bpf_ctx_narrow_access_ok(off, size, size_default);
+ }
+
+ return size == size_default;
+}
+
+static bool sock_filter_is_valid_access(int off, int size,
+ enum bpf_access_type type,
+ const struct bpf_prog *prog,
+ struct bpf_insn_access_aux *info)
+{
+ if (off < 0 || off >= sizeof(struct bpf_sock))
return false;
- /* The verifier guarantees that size > 0. */
if (off % size != 0)
return false;
- if (size != sizeof(__u32))
+ if (!__sock_filter_check_attach_type(off, type,
+ prog->expected_attach_type))
+ return false;
+ if (!__sock_filter_check_size(off, size, info))
return false;
-
return true;
}
@@ -4728,6 +4778,7 @@ static u32 sock_filter_convert_ctx_access(enum
bpf_access_type type,
struct bpf_prog *prog, u32
*target_size)
{
struct bpf_insn *insn = insn_buf;
+ int off;
switch (si->off) {
case offsetof(struct bpf_sock, bound_dev_if):
@@ -4783,6 +4834,43 @@ static u32 sock_filter_convert_ctx_access(enum
bpf_access_type type,
*insn++ = BPF_ALU32_IMM(BPF_AND, si->dst_reg, SK_FL_PROTO_MASK);
*insn++ = BPF_ALU32_IMM(BPF_RSH, si->dst_reg,
SK_FL_PROTO_SHIFT);
break;
+
+ case offsetof(struct bpf_sock, src_ip4):
+ *insn++ = BPF_LDX_MEM(
+ BPF_SIZE(si->code), si->dst_reg, si->src_reg,
+ bpf_target_off(struct sock_common, skc_rcv_saddr,
+ FIELD_SIZEOF(struct sock_common,
+ skc_rcv_saddr),
+ target_size));
+ break;
+
+ case bpf_ctx_range_till(struct bpf_sock, src_ip6[0], src_ip6[3]):
+#if IS_ENABLED(CONFIG_IPV6)
+ off = si->off;
+ off -= offsetof(struct bpf_sock, src_ip6[0]);
+ *insn++ = BPF_LDX_MEM(
+ BPF_SIZE(si->code), si->dst_reg, si->src_reg,
+ bpf_target_off(
+ struct sock_common,
+ skc_v6_rcv_saddr.s6_addr32[0],
+ FIELD_SIZEOF(struct sock_common,
+ skc_v6_rcv_saddr.s6_addr32[0]),
+ target_size) + off);
+#else
+ (void)off;
+ *insn++ = BPF_MOV32_IMM(si->dst_reg, 0);
+#endif
+ break;
+
+ case offsetof(struct bpf_sock, src_port):
+ *insn++ = BPF_LDX_MEM(
+ BPF_FIELD_SIZEOF(struct sock_common, skc_num),
+ si->dst_reg, si->src_reg,
+ bpf_target_off(struct sock_common, skc_num,
+ FIELD_SIZEOF(struct sock_common,
+ skc_num),
+ target_size));
+ break;
}
return insn - insn_buf;
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 488fe26ac8e5..142d4c35b493 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -519,12 +519,18 @@ int __inet_bind(struct sock *sk, struct sockaddr *uaddr,
int addr_len,
inet->inet_saddr = 0; /* Use device */
/* Make sure we are allowed to bind here. */
- if ((snum || !(inet->bind_address_no_port ||
- force_bind_address_no_port)) &&
- sk->sk_prot->get_port(sk, snum)) {
- inet->inet_saddr = inet->inet_rcv_saddr = 0;
- err = -EADDRINUSE;
- goto out_release_sock;
+ if (snum || !(inet->bind_address_no_port ||
+ force_bind_address_no_port)) {
+ if (sk->sk_prot->get_port(sk, snum)) {
+ inet->inet_saddr = inet->inet_rcv_saddr = 0;
+ err = -EADDRINUSE;
+ goto out_release_sock;
+ }
+ err = BPF_CGROUP_RUN_PROG_INET4_POST_BIND(sk);
+ if (err) {
+ inet->inet_saddr = inet->inet_rcv_saddr = 0;
+ goto out_release_sock;
+ }
}
if (inet->inet_rcv_saddr)
diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c
index 566cec0e0a44..41f50472679d 100644
--- a/net/ipv6/af_inet6.c
+++ b/net/ipv6/af_inet6.c
@@ -412,13 +412,20 @@ int __inet6_bind(struct sock *sk, struct sockaddr *uaddr,
int addr_len,
sk->sk_ipv6only = 1;
/* Make sure we are allowed to bind here. */
- if ((snum || !(inet->bind_address_no_port ||
- force_bind_address_no_port)) &&
- sk->sk_prot->get_port(sk, snum)) {
- sk->sk_ipv6only = saved_ipv6only;
- inet_reset_saddr(sk);
- err = -EADDRINUSE;
- goto out;
+ if (snum || !(inet->bind_address_no_port ||
+ force_bind_address_no_port)) {
+ if (sk->sk_prot->get_port(sk, snum)) {
+ sk->sk_ipv6only = saved_ipv6only;
+ inet_reset_saddr(sk);
+ err = -EADDRINUSE;
+ goto out;
+ }
+ err = BPF_CGROUP_RUN_PROG_INET6_POST_BIND(sk);
+ if (err) {
+ sk->sk_ipv6only = saved_ipv6only;
+ inet_reset_saddr(sk);
+ goto out;
+ }
}
if (addr_type != IPV6_ADDR_ANY)
--
2.9.5
