Sometimes it's handy to know when the socket gets freed.
In particular, we'd like to try to use a smarter allocation
of ports for bpf_bind and explore the possibility of
limiting the number of SOCK_DGRAM sockets the process can have.
Adding a release pair to existing BPF_CGROUP_INET_SOCK_CREATE
can unlock both of the mentioned features.
The only questionable part here is the sock->sk check
in the inet_release. Looking at the places where we
do 'sock->sk = NULL', I don't understand how it can race
with inet_release and why the check is there (it's been
there since the initial git import). Otherwise, the
change itself is pretty simple, we add a BPF hook
to the inet_release and avoid calling it for kernel
sockets.
v2:
* fix compile issue with CONFIG_CGROUP_BPF=n (kernel test robot)
Signed-off-by: Stanislav Fomichev <sdf@xxxxxxxxxx>
---
include/linux/bpf-cgroup.h | 4 ++++
include/uapi/linux/bpf.h | 1 +
kernel/bpf/syscall.c | 3 +++
net/core/filter.c | 1 +
net/ipv4/af_inet.c | 3 +++
5 files changed, 12 insertions(+)
diff --git a/include/linux/bpf-cgroup.h b/include/linux/bpf-cgroup.h
index c66c545e161a..2c6f26670acc 100644
--- a/include/linux/bpf-cgroup.h
+++ b/include/linux/bpf-cgroup.h
@@ -210,6 +210,9 @@ int bpf_percpu_cgroup_storage_update(struct bpf_map *map, void *key,
#define BPF_CGROUP_RUN_PROG_INET_SOCK(sk) \
BPF_CGROUP_RUN_SK_PROG(sk, BPF_CGROUP_INET_SOCK_CREATE)
+#define BPF_CGROUP_RUN_PROG_INET_SOCK_RELEASE(sk) \
+ BPF_CGROUP_RUN_SK_PROG(sk, BPF_CGROUP_INET_SOCK_RELEASE)
+
#define BPF_CGROUP_RUN_PROG_INET4_POST_BIND(sk) \
BPF_CGROUP_RUN_SK_PROG(sk, BPF_CGROUP_INET4_POST_BIND)
@@ -401,6 +404,7 @@ static inline int bpf_percpu_cgroup_storage_update(struct bpf_map *map,
#define BPF_CGROUP_RUN_PROG_INET_INGRESS(sk,skb) ({ 0; })
#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(sk, uaddr) ({ 0; })
#define BPF_CGROUP_RUN_PROG_INET6_BIND(sk, uaddr) ({ 0; })
#define BPF_CGROUP_RUN_PROG_INET4_POST_BIND(sk) ({ 0; })
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index c65b374a5090..d7aea1d0167a 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -226,6 +226,7 @@ enum bpf_attach_type {
BPF_CGROUP_INET4_GETSOCKNAME,
BPF_CGROUP_INET6_GETSOCKNAME,
BPF_XDP_DEVMAP,
+ BPF_CGROUP_INET_SOCK_RELEASE,
__MAX_BPF_ATTACH_TYPE
};
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 4d530b1d5683..2a3d4b8f95c7 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1994,6 +1994,7 @@ bpf_prog_load_check_attach(enum bpf_prog_type prog_type,
case BPF_PROG_TYPE_CGROUP_SOCK:
switch (expected_attach_type) {
case BPF_CGROUP_INET_SOCK_CREATE:
+ case BPF_CGROUP_INET_SOCK_RELEASE:
case BPF_CGROUP_INET4_POST_BIND:
case BPF_CGROUP_INET6_POST_BIND:
return 0;
@@ -2792,6 +2793,7 @@ attach_type_to_prog_type(enum bpf_attach_type attach_type)
return BPF_PROG_TYPE_CGROUP_SKB;
break;
case BPF_CGROUP_INET_SOCK_CREATE:
+ case BPF_CGROUP_INET_SOCK_RELEASE:
case BPF_CGROUP_INET4_POST_BIND:
case BPF_CGROUP_INET6_POST_BIND:
return BPF_PROG_TYPE_CGROUP_SOCK;
@@ -2942,6 +2944,7 @@ static int bpf_prog_query(const union bpf_attr *attr,
case BPF_CGROUP_INET_INGRESS:
case BPF_CGROUP_INET_EGRESS:
case BPF_CGROUP_INET_SOCK_CREATE:
+ case BPF_CGROUP_INET_SOCK_RELEASE:
case BPF_CGROUP_INET4_BIND:
case BPF_CGROUP_INET6_BIND:
case BPF_CGROUP_INET4_POST_BIND:
diff --git a/net/core/filter.c b/net/core/filter.c
index 209482a4eaa2..7bcac182383c 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -6855,6 +6855,7 @@ static bool __sock_filter_check_attach_type(int off,
case offsetof(struct bpf_sock, priority):
switch (attach_type) {
case BPF_CGROUP_INET_SOCK_CREATE:
+ case BPF_CGROUP_INET_SOCK_RELEASE:
goto full_access;
default:
return false;
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 02aa5cb3a4fd..965a96ea1168 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -411,6 +411,9 @@ int inet_release(struct socket *sock)
if (sk) {
long timeout;
+ if (!sk->sk_kern_sock)
+ BPF_CGROUP_RUN_PROG_INET_SOCK_RELEASE(sk);
+
/* Applications forget to leave groups before exiting */
ip_mc_drop_socket(sk);
--
2.27.0.212.ge8ba1cc988-goog
