Merge branch 'bpf-sk-storage-clone'

Stanislav Fomichev says:

====================
Currently there is no way to propagate sk storage from the listener
socket to a newly accepted one. Consider the following use case:

        fd = socket();
        setsockopt(fd, SOL_IP, IP_TOS,...);
        /* ^^^ setsockopt BPF program triggers here and saves something
         * into sk storage of the listener.
         */
        listen(fd, ...);
        while (client = accept(fd)) {
                /* At this point all association between listener
                 * socket and newly accepted one is gone. New
                 * socket will not have any sk storage attached.
                 */
        }

Let's add new BPF_F_CLONE flag that can be specified when creating
a socket storage map. This new flag indicates that map contents
should be cloned when the socket is cloned.

v4:
* drop 'goto err' in bpf_sk_storage_clone (Yonghong Song)
* add comment about race with bpf_sk_storage_map_free to the
  bpf_sk_storage_clone side as well (Daniel Borkmann)

v3:
* make sure BPF_F_NO_PREALLOC is always present when creating
  a map (Martin KaFai Lau)
* don't call bpf_sk_storage_free explicitly, rely on
  sk_free_unlock_clone to do the cleanup (Martin KaFai Lau)

v2:
* remove spinlocks around selem_link_map/sk (Martin KaFai Lau)
* BPF_F_CLONE on a map, not selem (Martin KaFai Lau)
* hold a map while cloning (Martin KaFai Lau)
* use BTF maps in selftests (Yonghong Song)
* do proper cleanup selftests; don't call close(-1) (Yonghong Song)
* export bpf_map_inc_not_zero
====================
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

include/linux/bpf.h

@@ -647,6 +647,8 @@ void bpf_map_free_id(struct bpf_map *map, bool do_idr_lock);
 struct bpf_map *bpf_map_get_with_uref(u32 ufd);
 struct bpf_map *__bpf_map_get(struct fd f);
 struct bpf_map * __must_check bpf_map_inc(struct bpf_map *map, bool uref);
+struct bpf_map * __must_check bpf_map_inc_not_zero(struct bpf_map *map,
+						   bool uref);
 void bpf_map_put_with_uref(struct bpf_map *map);
 void bpf_map_put(struct bpf_map *map);
 int bpf_map_charge_memlock(struct bpf_map *map, u32 pages);

include/net/bpf_sk_storage.h

@@ -10,4 +10,14 @@ void bpf_sk_storage_free(struct sock *sk);
 extern const struct bpf_func_proto bpf_sk_storage_get_proto;
 extern const struct bpf_func_proto bpf_sk_storage_delete_proto;
 
+#ifdef CONFIG_BPF_SYSCALL
+int bpf_sk_storage_clone(const struct sock *sk, struct sock *newsk);
+#else
+static inline int bpf_sk_storage_clone(const struct sock *sk,
+				       struct sock *newsk)
+{
+	return 0;
+}
+#endif
+
 #endif /* _BPF_SK_STORAGE_H */

include/uapi/linux/bpf.h

@@ -337,6 +337,9 @@ enum bpf_attach_type {
 #define BPF_F_RDONLY_PROG	(1U << 7)
 #define BPF_F_WRONLY_PROG	(1U << 8)
 
+/* Clone map from listener for newly accepted socket */
+#define BPF_F_CLONE		(1U << 9)
+
 /* flags for BPF_PROG_QUERY */
 #define BPF_F_QUERY_EFFECTIVE	(1U << 0)
 

kernel/bpf/syscall.c

@@ -683,7 +683,7 @@ struct bpf_map *bpf_map_get_with_uref(u32 ufd)
 }
 
 /* map_idr_lock should have been held */
-static struct bpf_map *bpf_map_inc_not_zero(struct bpf_map *map,
+static struct bpf_map *__bpf_map_inc_not_zero(struct bpf_map *map,
 					      bool uref)
 {
 	int refold;
@@ -704,6 +704,16 @@ static struct bpf_map *bpf_map_inc_not_zero(struct bpf_map *map,
 	return map;
 }
 
+struct bpf_map *bpf_map_inc_not_zero(struct bpf_map *map, bool uref)
+{
+	spin_lock_bh(&map_idr_lock);
+	map = __bpf_map_inc_not_zero(map, uref);
+	spin_unlock_bh(&map_idr_lock);
+
+	return map;
+}
+EXPORT_SYMBOL_GPL(bpf_map_inc_not_zero);
+
 int __weak bpf_stackmap_copy(struct bpf_map *map, void *key, void *value)
 {
 	return -ENOTSUPP;
@@ -2177,7 +2187,7 @@ static int bpf_map_get_fd_by_id(const union bpf_attr *attr)
 	spin_lock_bh(&map_idr_lock);
 	map = idr_find(&map_idr, id);
 	if (map)
-		map = bpf_map_inc_not_zero(map, true);
+		map = __bpf_map_inc_not_zero(map, true);
 	else
 		map = ERR_PTR(-ENOENT);
 	spin_unlock_bh(&map_idr_lock);

net/core/bpf_sk_storage.c

@@ -12,6 +12,9 @@
 
 static atomic_t cache_idx;
 
+#define SK_STORAGE_CREATE_FLAG_MASK					\
+	(BPF_F_NO_PREALLOC | BPF_F_CLONE)
+
 struct bucket {
 	struct hlist_head list;
 	raw_spinlock_t lock;
@@ -209,7 +212,6 @@ static void selem_unlink_sk(struct bpf_sk_storage_elem *selem)
 		kfree_rcu(sk_storage, rcu);
 }
 
-/* sk_storage->lock must be held and sk_storage->list cannot be empty */
 static void __selem_link_sk(struct bpf_sk_storage *sk_storage,
 			    struct bpf_sk_storage_elem *selem)
 {
@@ -509,7 +511,7 @@ static int sk_storage_delete(struct sock *sk, struct bpf_map *map)
 	return 0;
 }
 
-/* Called by __sk_destruct() */
+/* Called by __sk_destruct() & bpf_sk_storage_clone() */
 void bpf_sk_storage_free(struct sock *sk)
 {
 	struct bpf_sk_storage_elem *selem;
@@ -557,6 +559,11 @@ static void bpf_sk_storage_map_free(struct bpf_map *map)
 
 	smap = (struct bpf_sk_storage_map *)map;
 
+	/* Note that this map might be concurrently cloned from
+	 * bpf_sk_storage_clone. Wait for any existing bpf_sk_storage_clone
+	 * RCU read section to finish before proceeding. New RCU
+	 * read sections should be prevented via bpf_map_inc_not_zero.
+	 */
 	synchronize_rcu();
 
 	/* bpf prog and the userspace can no longer access this map
@@ -601,7 +608,9 @@ static void bpf_sk_storage_map_free(struct bpf_map *map)
 
 static int bpf_sk_storage_map_alloc_check(union bpf_attr *attr)
 {
-	if (attr->map_flags != BPF_F_NO_PREALLOC || attr->max_entries ||
+	if (attr->map_flags & ~SK_STORAGE_CREATE_FLAG_MASK ||
+	    !(attr->map_flags & BPF_F_NO_PREALLOC) ||
+	    attr->max_entries ||
 	    attr->key_size != sizeof(int) || !attr->value_size ||
 	    /* Enforce BTF for userspace sk dumping */
 	    !attr->btf_key_type_id || !attr->btf_value_type_id)
@@ -739,6 +748,95 @@ static int bpf_fd_sk_storage_delete_elem(struct bpf_map *map, void *key)
 	return err;
 }
 
+static struct bpf_sk_storage_elem *
+bpf_sk_storage_clone_elem(struct sock *newsk,
+			  struct bpf_sk_storage_map *smap,
+			  struct bpf_sk_storage_elem *selem)
+{
+	struct bpf_sk_storage_elem *copy_selem;
+
+	copy_selem = selem_alloc(smap, newsk, NULL, true);
+	if (!copy_selem)
+		return NULL;
+
+	if (map_value_has_spin_lock(&smap->map))
+		copy_map_value_locked(&smap->map, SDATA(copy_selem)->data,
+				      SDATA(selem)->data, true);
+	else
+		copy_map_value(&smap->map, SDATA(copy_selem)->data,
+			       SDATA(selem)->data);
+
+	return copy_selem;
+}
+
+int bpf_sk_storage_clone(const struct sock *sk, struct sock *newsk)
+{
+	struct bpf_sk_storage *new_sk_storage = NULL;
+	struct bpf_sk_storage *sk_storage;
+	struct bpf_sk_storage_elem *selem;
+	int ret = 0;
+
+	RCU_INIT_POINTER(newsk->sk_bpf_storage, NULL);
+
+	rcu_read_lock();
+	sk_storage = rcu_dereference(sk->sk_bpf_storage);
+
+	if (!sk_storage || hlist_empty(&sk_storage->list))
+		goto out;
+
+	hlist_for_each_entry_rcu(selem, &sk_storage->list, snode) {
+		struct bpf_sk_storage_elem *copy_selem;
+		struct bpf_sk_storage_map *smap;
+		struct bpf_map *map;
+
+		smap = rcu_dereference(SDATA(selem)->smap);
+		if (!(smap->map.map_flags & BPF_F_CLONE))
+			continue;
+
+		/* Note that for lockless listeners adding new element
+		 * here can race with cleanup in bpf_sk_storage_map_free.
+		 * Try to grab map refcnt to make sure that it's still
+		 * alive and prevent concurrent removal.
+		 */
+		map = bpf_map_inc_not_zero(&smap->map, false);
+		if (IS_ERR(map))
+			continue;
+
+		copy_selem = bpf_sk_storage_clone_elem(newsk, smap, selem);
+		if (!copy_selem) {
+			ret = -ENOMEM;
+			bpf_map_put(map);
+			goto out;
+		}
+
+		if (new_sk_storage) {
+			selem_link_map(smap, copy_selem);
+			__selem_link_sk(new_sk_storage, copy_selem);
+		} else {
+			ret = sk_storage_alloc(newsk, smap, copy_selem);
+			if (ret) {
+				kfree(copy_selem);
+				atomic_sub(smap->elem_size,
+					   &newsk->sk_omem_alloc);
+				bpf_map_put(map);
+				goto out;
+			}
+
+			new_sk_storage = rcu_dereference(copy_selem->sk_storage);
+		}
+		bpf_map_put(map);
+	}
+
+out:
+	rcu_read_unlock();
+
+	/* In case of an error, don't free anything explicitly here, the
+	 * caller is responsible to call bpf_sk_storage_free.
+	 */
+
+	return ret;
+}
+
 BPF_CALL_4(bpf_sk_storage_get, struct bpf_map *, map, struct sock *, sk,
 	   void *, value, u64, flags)
 {

net/core/sock.c

@@ -1851,9 +1851,12 @@ struct sock *sk_clone_lock(const struct sock *sk, const gfp_t priority)
 			goto out;
 		}
 		RCU_INIT_POINTER(newsk->sk_reuseport_cb, NULL);
-#ifdef CONFIG_BPF_SYSCALL
-		RCU_INIT_POINTER(newsk->sk_bpf_storage, NULL);
-#endif
+
+		if (bpf_sk_storage_clone(sk, newsk)) {
+			sk_free_unlock_clone(newsk);
+			newsk = NULL;
+			goto out;
+		}
 
 		newsk->sk_err	   = 0;
 		newsk->sk_err_soft = 0;

tools/include/uapi/linux/bpf.h

@@ -337,6 +337,9 @@ enum bpf_attach_type {
 #define BPF_F_RDONLY_PROG	(1U << 7)
 #define BPF_F_WRONLY_PROG	(1U << 8)
 
+/* Clone map from listener for newly accepted socket */
+#define BPF_F_CLONE		(1U << 9)
+
 /* flags for BPF_PROG_QUERY */
 #define BPF_F_QUERY_EFFECTIVE	(1U << 0)
 

tools/testing/selftests/bpf/.gitignore

@@ -42,4 +42,5 @@ xdping
 test_sockopt
 test_sockopt_sk
 test_sockopt_multi
+test_sockopt_inherit
 test_tcp_rtt

tools/testing/selftests/bpf/Makefile

@@ -29,7 +29,7 @@ TEST_GEN_PROGS = test_verifier test_tag test_maps test_lru_map test_lpm_map test
 	test_cgroup_storage test_select_reuseport test_section_names \
 	test_netcnt test_tcpnotify_user test_sock_fields test_sysctl test_hashmap \
 	test_btf_dump test_cgroup_attach xdping test_sockopt test_sockopt_sk \
-	test_sockopt_multi test_tcp_rtt
+	test_sockopt_multi test_sockopt_inherit test_tcp_rtt
 
 BPF_OBJ_FILES = $(patsubst %.c,%.o, $(notdir $(wildcard progs/*.c)))
 TEST_GEN_FILES = $(BPF_OBJ_FILES)
@@ -111,6 +111,7 @@ $(OUTPUT)/test_cgroup_attach: cgroup_helpers.c
 $(OUTPUT)/test_sockopt: cgroup_helpers.c
 $(OUTPUT)/test_sockopt_sk: cgroup_helpers.c
 $(OUTPUT)/test_sockopt_multi: cgroup_helpers.c
+$(OUTPUT)/test_sockopt_inherit: cgroup_helpers.c
 $(OUTPUT)/test_tcp_rtt: cgroup_helpers.c
 
 .PHONY: force

tools/testing/selftests/bpf/progs/sockopt_inherit.c

+// SPDX-License-Identifier: GPL-2.0
+#include <linux/bpf.h>
+#include "bpf_helpers.h"
+
+char _license[] SEC("license") = "GPL";
+__u32 _version SEC("version") = 1;
+
+#define SOL_CUSTOM			0xdeadbeef
+#define CUSTOM_INHERIT1			0
+#define CUSTOM_INHERIT2			1
+#define CUSTOM_LISTENER			2
+
+struct sockopt_inherit {
+	__u8 val;
+};
+
+struct {
+	__uint(type, BPF_MAP_TYPE_SK_STORAGE);
+	__uint(map_flags, BPF_F_NO_PREALLOC | BPF_F_CLONE);
+	__type(key, int);
+	__type(value, struct sockopt_inherit);
+} cloned1_map SEC(".maps");
+
+struct {
+	__uint(type, BPF_MAP_TYPE_SK_STORAGE);
+	__uint(map_flags, BPF_F_NO_PREALLOC | BPF_F_CLONE);
+	__type(key, int);
+	__type(value, struct sockopt_inherit);
+} cloned2_map SEC(".maps");
+
+struct {
+	__uint(type, BPF_MAP_TYPE_SK_STORAGE);
+	__uint(map_flags, BPF_F_NO_PREALLOC);
+	__type(key, int);
+	__type(value, struct sockopt_inherit);
+} listener_only_map SEC(".maps");
+
+static __inline struct sockopt_inherit *get_storage(struct bpf_sockopt *ctx)
+{
+	if (ctx->optname == CUSTOM_INHERIT1)
+		return bpf_sk_storage_get(&cloned1_map, ctx->sk, 0,
+					  BPF_SK_STORAGE_GET_F_CREATE);
+	else if (ctx->optname == CUSTOM_INHERIT2)
+		return bpf_sk_storage_get(&cloned2_map, ctx->sk, 0,
+					  BPF_SK_STORAGE_GET_F_CREATE);
+	else
+		return bpf_sk_storage_get(&listener_only_map, ctx->sk, 0,
+					  BPF_SK_STORAGE_GET_F_CREATE);
+}
+
+SEC("cgroup/getsockopt")
+int _getsockopt(struct bpf_sockopt *ctx)
+{
+	__u8 *optval_end = ctx->optval_end;
+	struct sockopt_inherit *storage;
+	__u8 *optval = ctx->optval;
+
+	if (ctx->level != SOL_CUSTOM)
+		return 1; /* only interested in SOL_CUSTOM */
+
+	if (optval + 1 > optval_end)
+		return 0; /* EPERM, bounds check */
+
+	storage = get_storage(ctx);
+	if (!storage)
+		return 0; /* EPERM, couldn't get sk storage */
+
+	ctx->retval = 0; /* Reset system call return value to zero */
+
+	optval[0] = storage->val;
+	ctx->optlen = 1;
+
+	return 1;
+}
+
+SEC("cgroup/setsockopt")
+int _setsockopt(struct bpf_sockopt *ctx)
+{
+	__u8 *optval_end = ctx->optval_end;
+	struct sockopt_inherit *storage;
+	__u8 *optval = ctx->optval;
+
+	if (ctx->level != SOL_CUSTOM)
+		return 1; /* only interested in SOL_CUSTOM */
+
+	if (optval + 1 > optval_end)
+		return 0; /* EPERM, bounds check */
+
+	storage = get_storage(ctx);
+	if (!storage)
+		return 0; /* EPERM, couldn't get sk storage */
+
+	storage->val = optval[0];
+	ctx->optlen = -1;
+
+	return 1;
+}

tools/testing/selftests/bpf/test_sockopt_inherit.c

+// SPDX-License-Identifier: GPL-2.0
+#include <error.h>
+#include <errno.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <pthread.h>
+
+#include <linux/filter.h>
+#include <bpf/bpf.h>
+#include <bpf/libbpf.h>
+
+#include "bpf_rlimit.h"
+#include "bpf_util.h"
+#include "cgroup_helpers.h"
+
+#define CG_PATH				"/sockopt_inherit"
+#define SOL_CUSTOM			0xdeadbeef
+#define CUSTOM_INHERIT1			0
+#define CUSTOM_INHERIT2			1
+#define CUSTOM_LISTENER			2
+
+static int connect_to_server(int server_fd)
+{
+	struct sockaddr_storage addr;
+	socklen_t len = sizeof(addr);
+	int fd;
+
+	fd = socket(AF_INET, SOCK_STREAM, 0);
+	if (fd < 0) {
+		log_err("Failed to create client socket");
+		return -1;
+	}
+
+	if (getsockname(server_fd, (struct sockaddr *)&addr, &len)) {
+		log_err("Failed to get server addr");
+		goto out;
+	}
+
+	if (connect(fd, (const struct sockaddr *)&addr, len) < 0) {
+		log_err("Fail to connect to server");
+		goto out;
+	}
+
+	return fd;
+
+out:
+	close(fd);
+	return -1;
+}
+
+static int verify_sockopt(int fd, int optname, const char *msg, char expected)
+{
+	socklen_t optlen = 1;
+	char buf = 0;
+	int err;
+
+	err = getsockopt(fd, SOL_CUSTOM, optname, &buf, &optlen);
+	if (err) {
+		log_err("%s: failed to call getsockopt", msg);
+		return 1;
+	}
+
+	printf("%s %d: got=0x%x ? expected=0x%x\n", msg, optname, buf, expected);
+
+	if (buf != expected) {
+		log_err("%s: unexpected getsockopt value %d != %d", msg,
+			buf, expected);
+		return 1;
+	}
+
+	return 0;
+}
+
+static void *server_thread(void *arg)
+{
+	struct sockaddr_storage addr;
+	socklen_t len = sizeof(addr);
+	int fd = *(int *)arg;
+	int client_fd;
+	int err = 0;
+
+	if (listen(fd, 1) < 0)
+		error(1, errno, "Failed to listed on socket");
+
+	err += verify_sockopt(fd, CUSTOM_INHERIT1, "listen", 1);
+	err += verify_sockopt(fd, CUSTOM_INHERIT2, "listen", 1);
+	err += verify_sockopt(fd, CUSTOM_LISTENER, "listen", 1);
+
+	client_fd = accept(fd, (struct sockaddr *)&addr, &len);
+	if (client_fd < 0)
+		error(1, errno, "Failed to accept client");
+
+	err += verify_sockopt(client_fd, CUSTOM_INHERIT1, "accept", 1);
+	err += verify_sockopt(client_fd, CUSTOM_INHERIT2, "accept", 1);
+	err += verify_sockopt(client_fd, CUSTOM_LISTENER, "accept", 0);
+
+	close(client_fd);
+
+	return (void *)(long)err;
+}
+
+static int start_server(void)
+{
+	struct sockaddr_in addr = {
+		.sin_family = AF_INET,
+		.sin_addr.s_addr = htonl(INADDR_LOOPBACK),
+	};
+	char buf;
+	int err;
+	int fd;
+	int i;
+
+	fd = socket(AF_INET, SOCK_STREAM, 0);
+	if (fd < 0) {
+		log_err("Failed to create server socket");
+		return -1;
+	}
+
+	for (i = CUSTOM_INHERIT1; i <= CUSTOM_LISTENER; i++) {
+		buf = 0x01;
+		err = setsockopt(fd, SOL_CUSTOM, i, &buf, 1);
+		if (err) {
+			log_err("Failed to call setsockopt(%d)", i);
+			close(fd);
+			return -1;
+		}
+	}
+
+	if (bind(fd, (const struct sockaddr *)&addr, sizeof(addr)) < 0) {
+		log_err("Failed to bind socket");
+		close(fd);
+		return -1;
+	}
+
+	return fd;
+}
+
+static int prog_attach(struct bpf_object *obj, int cgroup_fd, const char *title)
+{
+	enum bpf_attach_type attach_type;
+	enum bpf_prog_type prog_type;
+	struct bpf_program *prog;
+	int err;
+
+	err = libbpf_prog_type_by_name(title, &prog_type, &attach_type);
+	if (err) {
+		log_err("Failed to deduct types for %s BPF program", title);
+		return -1;
+	}
+
+	prog = bpf_object__find_program_by_title(obj, title);
+	if (!prog) {
+		log_err("Failed to find %s BPF program", title);
+		return -1;
+	}
+
+	err = bpf_prog_attach(bpf_program__fd(prog), cgroup_fd,
+			      attach_type, 0);
+	if (err) {
+		log_err("Failed to attach %s BPF program", title);
+		return -1;
+	}
+
+	return 0;
+}
+
+static int run_test(int cgroup_fd)
+{
+	struct bpf_prog_load_attr attr = {
+		.file = "./sockopt_inherit.o",
+	};
+	int server_fd = -1, client_fd;
+	struct bpf_object *obj;
+	void *server_err;
+	pthread_t tid;
+	int ignored;
+	int err;
+
+	err = bpf_prog_load_xattr(&attr, &obj, &ignored);
+	if (err) {
+		log_err("Failed to load BPF object");
+		return -1;
+	}
+
+	err = prog_attach(obj, cgroup_fd, "cgroup/getsockopt");
+	if (err)
+		goto close_bpf_object;
+
+	err = prog_attach(obj, cgroup_fd, "cgroup/setsockopt");
+	if (err)
+		goto close_bpf_object;
+
+	server_fd = start_server();
+	if (server_fd < 0) {
+		err = -1;
+		goto close_bpf_object;
+	}
+
+	pthread_create(&tid, NULL, server_thread, (void *)&server_fd);
+
+	client_fd = connect_to_server(server_fd);
+	if (client_fd < 0) {
+		err = -1;
+		goto close_server_fd;
+	}
+
+	err += verify_sockopt(client_fd, CUSTOM_INHERIT1, "connect", 0);
+	err += verify_sockopt(client_fd, CUSTOM_INHERIT2, "connect", 0);
+	err += verify_sockopt(client_fd, CUSTOM_LISTENER, "connect", 0);
+
+	pthread_join(tid, &server_err);
+
+	err += (int)(long)server_err;
+
+	close(client_fd);
+
+close_server_fd:
+	close(server_fd);
+close_bpf_object:
+	bpf_object__close(obj);
+	return err;
+}
+
+int main(int args, char **argv)
+{
+	int cgroup_fd;
+	int err = EXIT_SUCCESS;
+
+	if (setup_cgroup_environment())
+		return err;
+
+	cgroup_fd = create_and_get_cgroup(CG_PATH);
+	if (cgroup_fd < 0)
+		goto cleanup_cgroup_env;
+
+	if (join_cgroup(CG_PATH))
+		goto cleanup_cgroup;
+
+	if (run_test(cgroup_fd))
+		err = EXIT_FAILURE;
+
+	printf("test_sockopt_inherit: %s\n",
+	       err == EXIT_SUCCESS ? "PASSED" : "FAILED");
+
+cleanup_cgroup:
+	close(cgroup_fd);
+cleanup_cgroup_env:
+	cleanup_cgroup_environment();
+	return err;
+}