At the moment, BPF_CGROUP_INET{4,6}_BIND hooks can rewrite user_port
to the privileged ones (< ip_unprivileged_port_start), but it will
be rejected later on in the __inet_bind or __inet6_bind.
Let's export 'port_changed' event from the BPF program and bypass
ip_unprivileged_port_start range check when we've seen that
the program explicitly overrode the port. This is accomplished
by generating instructions to set ctx->port_changed along with
updating ctx->user_port.
Signed-off-by: Stanislav Fomichev <sdf@xxxxxxxxxx>
---
include/linux/bpf-cgroup.h | 30 ++++++++++++++++++++----------
include/linux/filter.h | 1 +
include/net/inet_common.h | 3 +++
kernel/bpf/cgroup.c | 8 +++++++-
net/core/filter.c | 13 +++++++++++++
net/ipv4/af_inet.c | 9 ++++++---
net/ipv6/af_inet6.c | 6 ++++--
7 files changed, 54 insertions(+), 16 deletions(-)
diff --git a/include/linux/bpf-cgroup.h b/include/linux/bpf-cgroup.h
index 0748fd87969e..874ed865bea1 100644
--- a/include/linux/bpf-cgroup.h
+++ b/include/linux/bpf-cgroup.h
@@ -125,7 +125,8 @@ int __cgroup_bpf_run_filter_sk(struct sock *sk,
int __cgroup_bpf_run_filter_sock_addr(struct sock *sk,
struct sockaddr *uaddr,
enum bpf_attach_type type,
- void *t_ctx);
+ void *t_ctx,
+ bool *port_changed);
int __cgroup_bpf_run_filter_sock_ops(struct sock *sk,
struct bpf_sock_ops_kern *sock_ops,
@@ -234,7 +235,7 @@ int bpf_percpu_cgroup_storage_update(struct bpf_map *map, void *key,
int __ret = 0; \
if (cgroup_bpf_enabled(type)) \
__ret = __cgroup_bpf_run_filter_sock_addr(sk, uaddr, type, \
- NULL); \
+ NULL, NULL); \
__ret; \
})
@@ -244,17 +245,27 @@ int bpf_percpu_cgroup_storage_update(struct bpf_map *map, void *key,
if (cgroup_bpf_enabled(type)) { \
lock_sock(sk); \
__ret = __cgroup_bpf_run_filter_sock_addr(sk, uaddr, type, \
- t_ctx); \
+ t_ctx, NULL); \
release_sock(sk); \
} \
__ret; \
})
-#define BPF_CGROUP_RUN_PROG_INET4_BIND_LOCK(sk, uaddr) \
- BPF_CGROUP_RUN_SA_PROG_LOCK(sk, uaddr, BPF_CGROUP_INET4_BIND, NULL)
-
-#define BPF_CGROUP_RUN_PROG_INET6_BIND_LOCK(sk, uaddr) \
- BPF_CGROUP_RUN_SA_PROG_LOCK(sk, uaddr, BPF_CGROUP_INET6_BIND, NULL)
+#define BPF_CGROUP_RUN_PROG_INET_BIND_LOCK(sk, uaddr, type, flags) \
+({ \
+ bool port_changed = false; \
+ int __ret = 0; \
+ if (cgroup_bpf_enabled(type)) { \
+ lock_sock(sk); \
+ __ret = __cgroup_bpf_run_filter_sock_addr(sk, uaddr, type, \
+ NULL, \
+ &port_changed); \
+ release_sock(sk); \
+ if (port_changed) \
+ *flags |= BIND_NO_CAP_NET_BIND_SERVICE; \
+ } \
+ __ret; \
+})
#define BPF_CGROUP_PRE_CONNECT_ENABLED(sk) \
((cgroup_bpf_enabled(BPF_CGROUP_INET4_CONNECT) || \
@@ -453,8 +464,7 @@ static inline int bpf_percpu_cgroup_storage_update(struct bpf_map *map,
#define BPF_CGROUP_RUN_PROG_INET_EGRESS(sk,skb) ({ 0; })
#define BPF_CGROUP_RUN_PROG_INET_SOCK(sk) ({ 0; })
#define BPF_CGROUP_RUN_PROG_INET_SOCK_RELEASE(sk) ({ 0; })
-#define BPF_CGROUP_RUN_PROG_INET4_BIND_LOCK(sk, uaddr) ({ 0; })
-#define BPF_CGROUP_RUN_PROG_INET6_BIND_LOCK(sk, uaddr) ({ 0; })
+#define BPF_CGROUP_RUN_PROG_INET_BIND_LOCK(sk, uaddr, type, flags) ({ 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; })
diff --git a/include/linux/filter.h b/include/linux/filter.h
index 5b3137d7b690..9bee8c057dd2 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -1258,6 +1258,7 @@ struct bpf_sock_addr_kern {
*/
u64 tmp_reg;
void *t_ctx; /* Attach type specific context. */
+ u32 port_changed;
};
struct bpf_sock_ops_kern {
diff --git a/include/net/inet_common.h b/include/net/inet_common.h
index cb2818862919..9ba935c15869 100644
--- a/include/net/inet_common.h
+++ b/include/net/inet_common.h
@@ -41,6 +41,9 @@ int inet_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len);
#define BIND_WITH_LOCK (1 << 1)
/* Called from BPF program. */
#define BIND_FROM_BPF (1 << 2)
+/* Skip CAP_NET_BIND_SERVICE check. */
+#define BIND_NO_CAP_NET_BIND_SERVICE (1 << 3)
+
int __inet_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len,
u32 flags);
int inet_getname(struct socket *sock, struct sockaddr *uaddr,
diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
index da649f20d6b2..f5d6205f1717 100644
--- a/kernel/bpf/cgroup.c
+++ b/kernel/bpf/cgroup.c
@@ -1055,6 +1055,8 @@ EXPORT_SYMBOL(__cgroup_bpf_run_filter_sk);
* @uaddr: sockaddr struct provided by user
* @type: The type of program to be exectuted
* @t_ctx: Pointer to attach type specific context
+ * @port_changed: Pointer to bool which will be set to 'true' when BPF
+ * program updates user_port
*
* socket is expected to be of type INET or INET6.
*
@@ -1064,7 +1066,8 @@ EXPORT_SYMBOL(__cgroup_bpf_run_filter_sk);
int __cgroup_bpf_run_filter_sock_addr(struct sock *sk,
struct sockaddr *uaddr,
enum bpf_attach_type type,
- void *t_ctx)
+ void *t_ctx,
+ bool *port_changed)
{
struct bpf_sock_addr_kern ctx = {
.sk = sk,
@@ -1089,6 +1092,9 @@ int __cgroup_bpf_run_filter_sock_addr(struct sock *sk,
cgrp = sock_cgroup_ptr(&sk->sk_cgrp_data);
ret = BPF_PROG_RUN_ARRAY(cgrp->bpf.effective[type], &ctx, BPF_PROG_RUN);
+ if (port_changed)
+ *port_changed = ctx.port_changed;
+
return ret == 1 ? 0 : -EPERM;
}
EXPORT_SYMBOL(__cgroup_bpf_run_filter_sock_addr);
diff --git a/net/core/filter.c b/net/core/filter.c
index 9ab94e90d660..b3dd02eb9551 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -9028,6 +9028,19 @@ static u32 sock_addr_convert_ctx_access(enum bpf_access_type type,
offsetof(struct sockaddr_in6, sin6_port));
BUILD_BUG_ON(sizeof_field(struct sockaddr_in, sin_port) !=
sizeof_field(struct sockaddr_in6, sin6_port));
+
+ /* Set bpf_sock_addr_kern->port_changed=1 whenever
+ * the port is updated from the BPF program.
+ */
+ if (type == BPF_WRITE) {
+ *insn++ = BPF_ST_MEM(BPF_FIELD_SIZEOF(struct bpf_sock_addr_kern,
+ port_changed),
+ si->dst_reg,
+ offsetof(struct bpf_sock_addr_kern,
+ port_changed),
+ 1);
+ }
+
/* Account for sin6_port being smaller than user_port. */
port_size = min(port_size, BPF_LDST_BYTES(si));
SOCK_ADDR_LOAD_OR_STORE_NESTED_FIELD_SIZE_OFF(
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 6ba2930ff49b..aaa94bea19c3 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -438,6 +438,7 @@ EXPORT_SYMBOL(inet_release);
int inet_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
{
struct sock *sk = sock->sk;
+ u32 flags = BIND_WITH_LOCK;
int err;
/* If the socket has its own bind function then use it. (RAW) */
@@ -450,11 +451,12 @@ int inet_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
/* BPF prog is run before any checks are done so that if the prog
* changes context in a wrong way it will be caught.
*/
- err = BPF_CGROUP_RUN_PROG_INET4_BIND_LOCK(sk, uaddr);
+ err = BPF_CGROUP_RUN_PROG_INET_BIND_LOCK(sk, uaddr,
+ BPF_CGROUP_INET4_BIND, &flags);
if (err)
return err;
- return __inet_bind(sk, uaddr, addr_len, BIND_WITH_LOCK);
+ return __inet_bind(sk, uaddr, addr_len, flags);
}
EXPORT_SYMBOL(inet_bind);
@@ -499,7 +501,8 @@ int __inet_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len,
snum = ntohs(addr->sin_port);
err = -EACCES;
- if (snum && inet_port_requires_bind_service(net, snum) &&
+ if (!(flags & BIND_NO_CAP_NET_BIND_SERVICE) &&
+ snum && inet_port_requires_bind_service(net, snum) &&
!ns_capable(net->user_ns, CAP_NET_BIND_SERVICE))
goto out;
diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c
index b9c654836b72..3e523c4f5226 100644
--- a/net/ipv6/af_inet6.c
+++ b/net/ipv6/af_inet6.c
@@ -439,6 +439,7 @@ static int __inet6_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len,
int inet6_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
{
struct sock *sk = sock->sk;
+ u32 flags = BIND_WITH_LOCK;
int err = 0;
/* If the socket has its own bind function then use it. */
@@ -451,11 +452,12 @@ int inet6_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
/* BPF prog is run before any checks are done so that if the prog
* changes context in a wrong way it will be caught.
*/
- err = BPF_CGROUP_RUN_PROG_INET6_BIND_LOCK(sk, uaddr);
+ err = BPF_CGROUP_RUN_PROG_INET_BIND_LOCK(sk, uaddr,
+ BPF_CGROUP_INET6_BIND, &flags);
if (err)
return err;
- return __inet6_bind(sk, uaddr, addr_len, BIND_WITH_LOCK);
+ return __inet6_bind(sk, uaddr, addr_len, flags);
}
EXPORT_SYMBOL(inet6_bind);
--
2.30.0.284.gd98b1dd5eaa7-goog
