Merge branch 'fix-sockmap-flow_dissector-uapi'

Lorenz Bauer says:

====================
Both sockmap and flow_dissector ingnore various arguments passed to
BPF_PROG_ATTACH and BPF_PROG_DETACH. We can fix the attach case by
checking that the unused arguments are zero. I considered requiring
target_fd to be -1 instead of 0, but this leads to a lot of churn
in selftests. There is also precedent in that bpf_iter already
expects 0 for a similar field. I think that we can come up with a
work around for fd 0 should we need to in the future.

The detach case is more problematic: both cgroups and lirc2 verify
that attach_bpf_fd matches the currently attached program. This
way you need access to the program fd to be able to remove it.
Neither sockmap nor flow_dissector do this. flow_dissector even
has a check for CAP_NET_ADMIN because of this. The patch set
addresses this by implementing the desired behaviour.

There is a possibility for user space breakage: any callers that
don't provide the correct fd will fail with ENOENT. For sockmap
the risk is low: even the selftests assume that sockmap works
the way I described. For flow_dissector the story is less
straightforward, and the selftests use a variety of arguments.

I've includes fixes tags for the oldest commits that allow an easy
backport, however the behaviour dates back to when sockmap and
flow_dissector were introduced. What is the best way to handle these?

This set is based on top of Jakub's work "bpf, netns: Prepare
for multi-prog attachment" available at
https://lore.kernel.org/bpf/87k0zwmhtb.fsf@cloudflare.com/T/

Since v1:
- Adjust selftests
- Implement detach behaviour
====================
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

include/linux/bpf-netns.h

@@ -33,7 +33,7 @@ int netns_bpf_prog_query(const union bpf_attr *attr,
 			 union bpf_attr __user *uattr);
 int netns_bpf_prog_attach(const union bpf_attr *attr,
 			  struct bpf_prog *prog);
-int netns_bpf_prog_detach(const union bpf_attr *attr);
+int netns_bpf_prog_detach(const union bpf_attr *attr, enum bpf_prog_type ptype);
 int netns_bpf_link_create(const union bpf_attr *attr,
 			  struct bpf_prog *prog);
 #else
@@ -49,7 +49,8 @@ static inline int netns_bpf_prog_attach(const union bpf_attr *attr,
 	return -EOPNOTSUPP;
 }
 
-static inline int netns_bpf_prog_detach(const union bpf_attr *attr)
+static inline int netns_bpf_prog_detach(const union bpf_attr *attr,
+					enum bpf_prog_type ptype)
 {
 	return -EOPNOTSUPP;
 }

include/linux/bpf.h

@@ -1543,13 +1543,16 @@ static inline void bpf_map_offload_map_free(struct bpf_map *map)
 #endif /* CONFIG_NET && CONFIG_BPF_SYSCALL */
 
 #if defined(CONFIG_BPF_STREAM_PARSER)
-int sock_map_prog_update(struct bpf_map *map, struct bpf_prog *prog, u32 which);
+int sock_map_prog_update(struct bpf_map *map, struct bpf_prog *prog,
+			 struct bpf_prog *old, u32 which);
 int sock_map_get_from_fd(const union bpf_attr *attr, struct bpf_prog *prog);
+int sock_map_prog_detach(const union bpf_attr *attr, enum bpf_prog_type ptype);
 void sock_map_unhash(struct sock *sk);
 void sock_map_close(struct sock *sk, long timeout);
 #else
 static inline int sock_map_prog_update(struct bpf_map *map,
-				       struct bpf_prog *prog, u32 which)
+				       struct bpf_prog *prog,
+				       struct bpf_prog *old, u32 which)
 {
 	return -EOPNOTSUPP;
 }
@@ -1559,6 +1562,12 @@ static inline int sock_map_get_from_fd(const union bpf_attr *attr,
 {
 	return -EINVAL;
 }
+
+static inline int sock_map_prog_detach(const union bpf_attr *attr,
+				       enum bpf_prog_type ptype)
+{
+	return -EOPNOTSUPP;
+}
 #endif /* CONFIG_BPF_STREAM_PARSER */
 
 #if defined(CONFIG_INET) && defined(CONFIG_BPF_SYSCALL)

include/linux/skmsg.h

@@ -430,6 +430,19 @@ static inline void psock_set_prog(struct bpf_prog **pprog,
 		bpf_prog_put(prog);
 }
 
+static inline int psock_replace_prog(struct bpf_prog **pprog,
+				     struct bpf_prog *prog,
+				     struct bpf_prog *old)
+{
+	if (cmpxchg(pprog, old, prog) != old)
+		return -ENOENT;
+
+	if (old)
+		bpf_prog_put(old);
+
+	return 0;
+}
+
 static inline void psock_progs_drop(struct sk_psock_progs *progs)
 {
 	psock_set_prog(&progs->msg_parser, NULL);

kernel/bpf/net_namespace.c

@@ -209,6 +209,9 @@ int netns_bpf_prog_attach(const union bpf_attr *attr, struct bpf_prog *prog)
 	struct net *net;
 	int ret;
 
+	if (attr->target_fd || attr->attach_flags || attr->replace_bpf_fd)
+		return -EINVAL;
+
 	type = to_netns_bpf_attach_type(attr->attach_type);
 	if (type < 0)
 		return -EINVAL;
@@ -266,7 +269,8 @@ int netns_bpf_prog_attach(const union bpf_attr *attr, struct bpf_prog *prog)
 
 /* Must be called with netns_bpf_mutex held. */
 static int __netns_bpf_prog_detach(struct net *net,
-				   enum netns_bpf_attach_type type)
+				   enum netns_bpf_attach_type type,
+				   struct bpf_prog *old)
 {
 	struct bpf_prog *attached;
 
@@ -275,7 +279,7 @@ static int __netns_bpf_prog_detach(struct net *net,
 		return -EINVAL;
 
 	attached = net->bpf.progs[type];
-	if (!attached)
+	if (!attached || attached != old)
 		return -ENOENT;
 	netns_bpf_run_array_detach(net, type);
 	net->bpf.progs[type] = NULL;
@@ -283,19 +287,29 @@ static int __netns_bpf_prog_detach(struct net *net,
 	return 0;
 }
 
-int netns_bpf_prog_detach(const union bpf_attr *attr)
+int netns_bpf_prog_detach(const union bpf_attr *attr, enum bpf_prog_type ptype)
 {
 	enum netns_bpf_attach_type type;
+	struct bpf_prog *prog;
 	int ret;
 
+	if (attr->target_fd)
+		return -EINVAL;
+
 	type = to_netns_bpf_attach_type(attr->attach_type);
 	if (type < 0)
 		return -EINVAL;
 
+	prog = bpf_prog_get_type(attr->attach_bpf_fd, ptype);
+	if (IS_ERR(prog))
+		return PTR_ERR(prog);
+
 	mutex_lock(&netns_bpf_mutex);
-	ret = __netns_bpf_prog_detach(current->nsproxy->net_ns, type);
+	ret = __netns_bpf_prog_detach(current->nsproxy->net_ns, type, prog);
 	mutex_unlock(&netns_bpf_mutex);
 
+	bpf_prog_put(prog);
+
 	return ret;
 }
 

kernel/bpf/syscall.c

@@ -2893,13 +2893,11 @@ static int bpf_prog_detach(const union bpf_attr *attr)
 	switch (ptype) {
 	case BPF_PROG_TYPE_SK_MSG:
 	case BPF_PROG_TYPE_SK_SKB:
-		return sock_map_get_from_fd(attr, NULL);
+		return sock_map_prog_detach(attr, ptype);
 	case BPF_PROG_TYPE_LIRC_MODE2:
 		return lirc_prog_detach(attr);
 	case BPF_PROG_TYPE_FLOW_DISSECTOR:
-		if (!capable(CAP_NET_ADMIN))
-			return -EPERM;
-		return netns_bpf_prog_detach(attr);
+		return netns_bpf_prog_detach(attr, ptype);
 	case BPF_PROG_TYPE_CGROUP_DEVICE:
 	case BPF_PROG_TYPE_CGROUP_SKB:
 	case BPF_PROG_TYPE_CGROUP_SOCK:

net/core/sock_map.c

@@ -70,11 +70,49 @@ int sock_map_get_from_fd(const union bpf_attr *attr, struct bpf_prog *prog)
 	struct fd f;
 	int ret;
 
+	if (attr->attach_flags || attr->replace_bpf_fd)
+		return -EINVAL;
+
 	f = fdget(ufd);
 	map = __bpf_map_get(f);
 	if (IS_ERR(map))
 		return PTR_ERR(map);
-	ret = sock_map_prog_update(map, prog, attr->attach_type);
+	ret = sock_map_prog_update(map, prog, NULL, attr->attach_type);
+	fdput(f);
+	return ret;
+}
+
+int sock_map_prog_detach(const union bpf_attr *attr, enum bpf_prog_type ptype)
+{
+	u32 ufd = attr->target_fd;
+	struct bpf_prog *prog;
+	struct bpf_map *map;
+	struct fd f;
+	int ret;
+
+	if (attr->attach_flags || attr->replace_bpf_fd)
+		return -EINVAL;
+
+	f = fdget(ufd);
+	map = __bpf_map_get(f);
+	if (IS_ERR(map))
+		return PTR_ERR(map);
+
+	prog = bpf_prog_get(attr->attach_bpf_fd);
+	if (IS_ERR(prog)) {
+		ret = PTR_ERR(prog);
+		goto put_map;
+	}
+
+	if (prog->type != ptype) {
+		ret = -EINVAL;
+		goto put_prog;
+	}
+
+	ret = sock_map_prog_update(map, NULL, prog, attr->attach_type);
+put_prog:
+	bpf_prog_put(prog);
+put_map:
 	fdput(f);
 	return ret;
 }
@@ -1203,27 +1241,32 @@ static struct sk_psock_progs *sock_map_progs(struct bpf_map *map)
 }
 
 int sock_map_prog_update(struct bpf_map *map, struct bpf_prog *prog,
-			 u32 which)
+			 struct bpf_prog *old, u32 which)
 {
 	struct sk_psock_progs *progs = sock_map_progs(map);
+	struct bpf_prog **pprog;
 
 	if (!progs)
 		return -EOPNOTSUPP;
 
 	switch (which) {
 	case BPF_SK_MSG_VERDICT:
-		psock_set_prog(&progs->msg_parser, prog);
+		pprog = &progs->msg_parser;
 		break;
 	case BPF_SK_SKB_STREAM_PARSER:
-		psock_set_prog(&progs->skb_parser, prog);
+		pprog = &progs->skb_parser;
 		break;
 	case BPF_SK_SKB_STREAM_VERDICT:
-		psock_set_prog(&progs->skb_verdict, prog);
+		pprog = &progs->skb_verdict;
 		break;
 	default:
 		return -EOPNOTSUPP;
 	}
 
+	if (old)
+		return psock_replace_prog(pprog, prog, old);
+
+	psock_set_prog(pprog, prog);
 	return 0;
 }
 

tools/testing/selftests/bpf/prog_tests/flow_dissector.c

@@ -527,8 +527,8 @@ static void test_skb_less_prog_attach(struct bpf_flow *skel, int tap_fd)
 
 	run_tests_skb_less(tap_fd, skel->maps.last_dissection);
 
-	err = bpf_prog_detach(prog_fd, BPF_FLOW_DISSECTOR);
-	CHECK(err, "bpf_prog_detach", "err %d errno %d\n", err, errno);
+	err = bpf_prog_detach2(prog_fd, 0, BPF_FLOW_DISSECTOR);
+	CHECK(err, "bpf_prog_detach2", "err %d errno %d\n", err, errno);
 }
 
 static void test_skb_less_link_create(struct bpf_flow *skel, int tap_fd)

tools/testing/selftests/bpf/prog_tests/flow_dissector_reattach.c

@@ -113,7 +113,7 @@ static void test_prog_attach_prog_attach(int netns, int prog1, int prog2)
 	CHECK_FAIL(query_attached_prog_id(netns) != query_prog_id(prog2));
 
 out_detach:
-	err = bpf_prog_detach(0, BPF_FLOW_DISSECTOR);
+	err = bpf_prog_detach2(prog2, 0, BPF_FLOW_DISSECTOR);
 	if (CHECK_FAIL(err))
 		perror("bpf_prog_detach");
 	CHECK_FAIL(prog_is_attached(netns));
@@ -149,7 +149,7 @@ static void test_prog_attach_link_create(int netns, int prog1, int prog2)
 	DECLARE_LIBBPF_OPTS(bpf_link_create_opts, opts);
 	int err, link;
 
-	err = bpf_prog_attach(prog1, -1, BPF_FLOW_DISSECTOR, 0);
+	err = bpf_prog_attach(prog1, 0, BPF_FLOW_DISSECTOR, 0);
 	if (CHECK_FAIL(err)) {
 		perror("bpf_prog_attach(prog1)");
 		return;
@@ -165,7 +165,7 @@ static void test_prog_attach_link_create(int netns, int prog1, int prog2)
 		close(link);
 	CHECK_FAIL(query_attached_prog_id(netns) != query_prog_id(prog1));
 
-	err = bpf_prog_detach(-1, BPF_FLOW_DISSECTOR);
+	err = bpf_prog_detach2(prog1, 0, BPF_FLOW_DISSECTOR);
 	if (CHECK_FAIL(err))
 		perror("bpf_prog_detach");
 	CHECK_FAIL(prog_is_attached(netns));
@@ -185,7 +185,7 @@ static void test_link_create_prog_attach(int netns, int prog1, int prog2)
 
 	/* Expect failure attaching prog when link exists */
 	errno = 0;
-	err = bpf_prog_attach(prog2, -1, BPF_FLOW_DISSECTOR, 0);
+	err = bpf_prog_attach(prog2, 0, BPF_FLOW_DISSECTOR, 0);
 	if (CHECK_FAIL(!err || errno != EEXIST))
 		perror("bpf_prog_attach(prog2) expected EEXIST");
 	CHECK_FAIL(query_attached_prog_id(netns) != query_prog_id(prog1));
@@ -208,7 +208,7 @@ static void test_link_create_prog_detach(int netns, int prog1, int prog2)
 
 	/* Expect failure detaching prog when link exists */
 	errno = 0;
-	err = bpf_prog_detach(-1, BPF_FLOW_DISSECTOR);
+	err = bpf_prog_detach2(prog1, 0, BPF_FLOW_DISSECTOR);
 	if (CHECK_FAIL(!err || errno != EINVAL))
 		perror("bpf_prog_detach expected EINVAL");
 	CHECK_FAIL(query_attached_prog_id(netns) != query_prog_id(prog1));
@@ -228,7 +228,7 @@ static void test_prog_attach_detach_query(int netns, int prog1, int prog2)
 	}
 	CHECK_FAIL(query_attached_prog_id(netns) != query_prog_id(prog1));
 
-	err = bpf_prog_detach(0, BPF_FLOW_DISSECTOR);
+	err = bpf_prog_detach2(prog1, 0, BPF_FLOW_DISSECTOR);
 	if (CHECK_FAIL(err)) {
 		perror("bpf_prog_detach");
 		return;