Merge branch 'xdp-bpf-fixes'

John Fastabend says:

====================
net: Fixes for XDP/BPF

The following fixes, UAPI updates, and small improvement,

i. XDP needs to be called inside RCU with preempt disabled.

ii. Not strictly a bug fix but we have an attach command in the
sockmap UAPI already to avoid having a single kernel released with
only the attach and not the detach I'm pushing this into net branch.
Its early in the RC cycle so I think this is OK (not ideal but better
than supporting a UAPI with a missing detach forever).

iii. Final patch replace cpu_relax with cond_resched in devmap.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/bpf.h

@@ -385,16 +385,16 @@ static inline void __dev_map_flush(struct bpf_map *map)
 
 #if defined(CONFIG_STREAM_PARSER) && defined(CONFIG_BPF_SYSCALL)
 struct sock  *__sock_map_lookup_elem(struct bpf_map *map, u32 key);
-int sock_map_attach_prog(struct bpf_map *map, struct bpf_prog *prog, u32 type);
+int sock_map_prog(struct bpf_map *map, struct bpf_prog *prog, u32 type);
 #else
 static inline struct sock  *__sock_map_lookup_elem(struct bpf_map *map, u32 key)
 {
 	return NULL;
 }
 
-static inline int sock_map_attach_prog(struct bpf_map *map,
-				       struct bpf_prog *prog,
-				       u32 type)
+static inline int sock_map_prog(struct bpf_map *map,
+				struct bpf_prog *prog,
+				u32 type)
 {
 	return -EOPNOTSUPP;
 }

kernel/bpf/devmap.c

@@ -159,7 +159,7 @@ static void dev_map_free(struct bpf_map *map)
 		unsigned long *bitmap = per_cpu_ptr(dtab->flush_needed, cpu);
 
 		while (!bitmap_empty(bitmap, dtab->map.max_entries))
-			cpu_relax();
+			cond_resched();
 	}
 
 	for (i = 0; i < dtab->map.max_entries; i++) {

kernel/bpf/sockmap.c

@@ -792,7 +792,7 @@ static int sock_map_ctx_update_elem(struct bpf_sock_ops_kern *skops,
 	return err;
 }
 
-int sock_map_attach_prog(struct bpf_map *map, struct bpf_prog *prog, u32 type)
+int sock_map_prog(struct bpf_map *map, struct bpf_prog *prog, u32 type)
 {
 	struct bpf_stab *stab = container_of(map, struct bpf_stab, map);
 	struct bpf_prog *orig;

kernel/bpf/syscall.c

@@ -1096,10 +1096,10 @@ static int bpf_obj_get(const union bpf_attr *attr)
 
 #define BPF_PROG_ATTACH_LAST_FIELD attach_flags
 
-static int sockmap_get_from_fd(const union bpf_attr *attr)
+static int sockmap_get_from_fd(const union bpf_attr *attr, bool attach)
 {
+	struct bpf_prog *prog = NULL;
 	int ufd = attr->target_fd;
-	struct bpf_prog *prog;
 	struct bpf_map *map;
 	struct fd f;
 	int err;
@@ -1109,16 +1109,20 @@ static int sockmap_get_from_fd(const union bpf_attr *attr)
 	if (IS_ERR(map))
 		return PTR_ERR(map);
 
-	prog = bpf_prog_get_type(attr->attach_bpf_fd, BPF_PROG_TYPE_SK_SKB);
-	if (IS_ERR(prog)) {
-		fdput(f);
-		return PTR_ERR(prog);
+	if (attach) {
+		prog = bpf_prog_get_type(attr->attach_bpf_fd,
+					 BPF_PROG_TYPE_SK_SKB);
+		if (IS_ERR(prog)) {
+			fdput(f);
+			return PTR_ERR(prog);
+		}
 	}
 
-	err = sock_map_attach_prog(map, prog, attr->attach_type);
+	err = sock_map_prog(map, prog, attr->attach_type);
 	if (err) {
 		fdput(f);
-		bpf_prog_put(prog);
+		if (prog)
+			bpf_prog_put(prog);
 		return err;
 	}
 
@@ -1155,7 +1159,7 @@ static int bpf_prog_attach(const union bpf_attr *attr)
 		break;
 	case BPF_SK_SKB_STREAM_PARSER:
 	case BPF_SK_SKB_STREAM_VERDICT:
-		return sockmap_get_from_fd(attr);
+		return sockmap_get_from_fd(attr, true);
 	default:
 		return -EINVAL;
 	}
@@ -1204,7 +1208,10 @@ static int bpf_prog_detach(const union bpf_attr *attr)
 		ret = cgroup_bpf_update(cgrp, NULL, attr->attach_type, false);
 		cgroup_put(cgrp);
 		break;
-
+	case BPF_SK_SKB_STREAM_PARSER:
+	case BPF_SK_SKB_STREAM_VERDICT:
+		ret = sockmap_get_from_fd(attr, false);
+		break;
 	default:
 		return -EINVAL;
 	}

net/core/dev.c

@@ -3981,8 +3981,13 @@ static int netif_rx_internal(struct sk_buff *skb)
 	trace_netif_rx(skb);
 
 	if (static_key_false(&generic_xdp_needed)) {
-		int ret = do_xdp_generic(rcu_dereference(skb->dev->xdp_prog),
-					 skb);
+		int ret;
+
+		preempt_disable();
+		rcu_read_lock();
+		ret = do_xdp_generic(rcu_dereference(skb->dev->xdp_prog), skb);
+		rcu_read_unlock();
+		preempt_enable();
 
 		/* Consider XDP consuming the packet a success from
 		 * the netdev point of view we do not want to count
@@ -4500,18 +4505,20 @@ static int netif_receive_skb_internal(struct sk_buff *skb)
 	if (skb_defer_rx_timestamp(skb))
 		return NET_RX_SUCCESS;
 
-	rcu_read_lock();
-
 	if (static_key_false(&generic_xdp_needed)) {
-		int ret = do_xdp_generic(rcu_dereference(skb->dev->xdp_prog),
-					 skb);
+		int ret;
 
-		if (ret != XDP_PASS) {
-			rcu_read_unlock();
+		preempt_disable();
+		rcu_read_lock();
+		ret = do_xdp_generic(rcu_dereference(skb->dev->xdp_prog), skb);
+		rcu_read_unlock();
+		preempt_enable();
+
+		if (ret != XDP_PASS)
 			return NET_RX_DROP;
-		}
 	}
 
+	rcu_read_lock();
 #ifdef CONFIG_RPS
 	if (static_key_false(&rps_needed)) {
 		struct rps_dev_flow voidflow, *rflow = &voidflow;

tools/testing/selftests/bpf/test_maps.c

@@ -558,7 +558,7 @@ static void test_sockmap(int tasks, void *data)
 		}
 	}
 
-	/* Test attaching bad fds */
+	/* Test attaching/detaching bad fds */
 	err = bpf_prog_attach(-1, fd, BPF_SK_SKB_STREAM_PARSER, 0);
 	if (!err) {
 		printf("Failed invalid parser prog attach\n");
@@ -571,6 +571,30 @@ static void test_sockmap(int tasks, void *data)
 		goto out_sockmap;
 	}
 
+	err = bpf_prog_attach(-1, fd, __MAX_BPF_ATTACH_TYPE, 0);
+	if (!err) {
+		printf("Failed unknown prog attach\n");
+		goto out_sockmap;
+	}
+
+	err = bpf_prog_detach(fd, BPF_SK_SKB_STREAM_PARSER);
+	if (err) {
+		printf("Failed empty parser prog detach\n");
+		goto out_sockmap;
+	}
+
+	err = bpf_prog_detach(fd, BPF_SK_SKB_STREAM_VERDICT);
+	if (err) {
+		printf("Failed empty verdict prog detach\n");
+		goto out_sockmap;
+	}
+
+	err = bpf_prog_detach(fd, __MAX_BPF_ATTACH_TYPE);
+	if (!err) {
+		printf("Detach invalid prog successful\n");
+		goto out_sockmap;
+	}
+
 	/* Load SK_SKB program and Attach */
 	err = bpf_prog_load(SOCKMAP_PARSE_PROG,
 			    BPF_PROG_TYPE_SK_SKB, &obj, &parse_prog);
@@ -643,6 +667,13 @@ static void test_sockmap(int tasks, void *data)
 		goto out_sockmap;
 	}
 
+	err = bpf_prog_attach(verdict_prog, map_fd_rx,
+			      __MAX_BPF_ATTACH_TYPE, 0);
+	if (!err) {
+		printf("Attached unknown bpf prog\n");
+		goto out_sockmap;
+	}
+
 	/* Test map update elem afterwards fd lives in fd and map_fd */
 	for (i = 0; i < 6; i++) {
 		err = bpf_map_update_elem(map_fd_rx, &i, &sfd[i], BPF_ANY);
@@ -809,6 +840,24 @@ static void test_sockmap(int tasks, void *data)
 		assert(status == 0);
 	}
 
+	err = bpf_prog_detach(map_fd_rx, __MAX_BPF_ATTACH_TYPE);
+	if (!err) {
+		printf("Detached an invalid prog type.\n");
+		goto out_sockmap;
+	}
+
+	err = bpf_prog_detach(map_fd_rx, BPF_SK_SKB_STREAM_PARSER);
+	if (err) {
+		printf("Failed parser prog detach\n");
+		goto out_sockmap;
+	}
+
+	err = bpf_prog_detach(map_fd_rx, BPF_SK_SKB_STREAM_VERDICT);
+	if (err) {
+		printf("Failed parser prog detach\n");
+		goto out_sockmap;
+	}
+
 	/* Test map close sockets */
 	for (i = 0; i < 6; i++)
 		close(sfd[i]);