Merge branch 'bpf-next'

Daniel Borkmann says:

====================
BPF helper improvements and cleanups

This set adds various improvements to BPF helpers, a cleanup to use
skb_pkt_type_ok() helper, addition of bpf_skb_change_tail(), a follow
up for event output helper and removing ifdefs around the cgroupv2
helper bits. For details please see individual patches.

The set is based against net-next tree, but requires a merge of net
into net-next first.

Thanks a lot!
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 204 insertions, 12 deletions

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 0f665cb26b50..7047448e8129 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -2295,7 +2295,7 @@ static inline int pskb_network_may_pull(struct sk_buff *skb, unsigned int len)
 
 int ___pskb_trim(struct sk_buff *skb, unsigned int len);
 
-static inline void __skb_trim(struct sk_buff *skb, unsigned int len)
+static inline void __skb_set_length(struct sk_buff *skb, unsigned int len)
 {
 	if (unlikely(skb_is_nonlinear(skb))) {
 		WARN_ON(1);
@@ -2305,6 +2305,11 @@ static inline void __skb_trim(struct sk_buff *skb, unsigned int len)
 	skb_set_tail_pointer(skb, len);
 }
 
+static inline void __skb_trim(struct sk_buff *skb, unsigned int len)
+{
+	__skb_set_length(skb, len);
+}
+
 void skb_trim(struct sk_buff *skb, unsigned int len);
 
 static inline int __pskb_trim(struct sk_buff *skb, unsigned int len)
@@ -2335,6 +2340,20 @@ static inline void pskb_trim_unique(struct sk_buff *skb, unsigned int len)
 	BUG_ON(err);
 }
 
+static inline int __skb_grow(struct sk_buff *skb, unsigned int len)
+{
+	unsigned int diff = len - skb->len;
+
+	if (skb_tailroom(skb) < diff) {
+		int ret = pskb_expand_head(skb, 0, diff - skb_tailroom(skb),
+					   GFP_ATOMIC);
+		if (ret)
+			return ret;
+	}
+	__skb_set_length(skb, len);
+	return 0;
+}
+
 /**
  *	skb_orphan - orphan a buffer
  *	@skb: buffer to orphan
@@ -2938,6 +2957,21 @@ static inline int pskb_trim_rcsum(struct sk_buff *skb, unsigned int len)
 	return __pskb_trim(skb, len);
 }
 
+static inline int __skb_trim_rcsum(struct sk_buff *skb, unsigned int len)
+{
+	if (skb->ip_summed == CHECKSUM_COMPLETE)
+		skb->ip_summed = CHECKSUM_NONE;
+	__skb_trim(skb, len);
+	return 0;
+}
+
+static inline int __skb_grow_rcsum(struct sk_buff *skb, unsigned int len)
+{
+	if (skb->ip_summed == CHECKSUM_COMPLETE)
+		skb->ip_summed = CHECKSUM_NONE;
+	return __skb_grow(skb, len);
+}
+
 #define skb_queue_walk(queue, skb) \
 		for (skb = (queue)->next;					\
 		     skb != (struct sk_buff *)(queue);				\
@@ -3726,6 +3760,13 @@ static inline bool skb_is_gso_v6(const struct sk_buff *skb)
 	return skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6;
 }
 
+static inline void skb_gso_reset(struct sk_buff *skb)
+{
+	skb_shinfo(skb)->gso_size = 0;
+	skb_shinfo(skb)->gso_segs = 0;
+	skb_shinfo(skb)->gso_type = 0;
+}
+
 void __skb_warn_lro_forwarding(const struct sk_buff *skb);
 
 static inline bool skb_warn_if_lro(const struct sk_buff *skb)
diff --git a/include/net/sock.h b/include/net/sock.h
index ff5be7e8ddea..2aab9b63bf16 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1114,6 +1114,16 @@ static inline bool sk_stream_is_writeable(const struct sock *sk)
 	       sk_stream_memory_free(sk);
 }
 
+static inline int sk_under_cgroup_hierarchy(struct sock *sk,
+					    struct cgroup *ancestor)
+{
+#ifdef CONFIG_SOCK_CGROUP_DATA
+	return cgroup_is_descendant(sock_cgroup_ptr(&sk->sk_cgrp_data),
+				    ancestor);
+#else
+	return -ENOTSUPP;
+#endif
+}
 
 static inline bool sk_has_memory_pressure(const struct sock *sk)
 {
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 866d53c33298..e4c5a1baa993 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -386,6 +386,17 @@ enum bpf_func_id {
 	 */
 	BPF_FUNC_current_task_under_cgroup,
 
+	/**
+	 * bpf_skb_change_tail(skb, len, flags)
+	 * The helper will resize the skb to the given new size,
+	 * to be used f.e. with control messages.
+	 * @skb: pointer to skb
+	 * @len: new skb length
+	 * @flags: reserved
+	 * Return: 0 on success or negative error
+	 */
+	BPF_FUNC_skb_change_tail,
+
 	__BPF_FUNC_MAX_ID,
 };
 
diff --git a/net/core/filter.c b/net/core/filter.c
index cb06aceb512a..a83766be1ad2 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -1350,14 +1350,18 @@ struct bpf_scratchpad {
 
 static DEFINE_PER_CPU(struct bpf_scratchpad, bpf_sp);
 
+static inline int __bpf_try_make_writable(struct sk_buff *skb,
+					  unsigned int write_len)
+{
+	return skb_ensure_writable(skb, write_len);
+}
+
 static inline int bpf_try_make_writable(struct sk_buff *skb,
 					unsigned int write_len)
 {
-	int err;
+	int err = __bpf_try_make_writable(skb, write_len);
 
-	err = skb_ensure_writable(skb, write_len);
 	bpf_compute_data_end(skb);
-
 	return err;
 }
 
@@ -1976,8 +1980,8 @@ static u64 bpf_skb_change_type(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
 	u32 pkt_type = r2;
 
 	/* We only allow a restricted subset to be changed for now. */
-	if (unlikely(skb->pkt_type > PACKET_OTHERHOST ||
-		     pkt_type > PACKET_OTHERHOST))
+	if (unlikely(!skb_pkt_type_ok(skb->pkt_type) ||
+		     !skb_pkt_type_ok(pkt_type)))
 		return -EINVAL;
 
 	skb->pkt_type = pkt_type;
@@ -1992,6 +1996,92 @@ static const struct bpf_func_proto bpf_skb_change_type_proto = {
 	.arg2_type	= ARG_ANYTHING,
 };
 
+static u32 __bpf_skb_min_len(const struct sk_buff *skb)
+{
+	u32 min_len = skb_network_offset(skb);
+
+	if (skb_transport_header_was_set(skb))
+		min_len = skb_transport_offset(skb);
+	if (skb->ip_summed == CHECKSUM_PARTIAL)
+		min_len = skb_checksum_start_offset(skb) +
+			  skb->csum_offset + sizeof(__sum16);
+	return min_len;
+}
+
+static u32 __bpf_skb_max_len(const struct sk_buff *skb)
+{
+	return skb->dev ? skb->dev->mtu + skb->dev->hard_header_len :
+	       65536;
+}
+
+static int bpf_skb_grow_rcsum(struct sk_buff *skb, unsigned int new_len)
+{
+	unsigned int old_len = skb->len;
+	int ret;
+
+	ret = __skb_grow_rcsum(skb, new_len);
+	if (!ret)
+		memset(skb->data + old_len, 0, new_len - old_len);
+	return ret;
+}
+
+static int bpf_skb_trim_rcsum(struct sk_buff *skb, unsigned int new_len)
+{
+	return __skb_trim_rcsum(skb, new_len);
+}
+
+static u64 bpf_skb_change_tail(u64 r1, u64 r2, u64 flags, u64 r4, u64 r5)
+{
+	struct sk_buff *skb = (struct sk_buff *)(long) r1;
+	u32 max_len = __bpf_skb_max_len(skb);
+	u32 min_len = __bpf_skb_min_len(skb);
+	u32 new_len = (u32) r2;
+	int ret;
+
+	if (unlikely(flags || new_len > max_len || new_len < min_len))
+		return -EINVAL;
+	if (skb->encapsulation)
+		return -ENOTSUPP;
+
+	/* The basic idea of this helper is that it's performing the
+	 * needed work to either grow or trim an skb, and eBPF program
+	 * rewrites the rest via helpers like bpf_skb_store_bytes(),
+	 * bpf_lX_csum_replace() and others rather than passing a raw
+	 * buffer here. This one is a slow path helper and intended
+	 * for replies with control messages.
+	 *
+	 * Like in bpf_skb_change_proto(), we want to keep this rather
+	 * minimal and without protocol specifics so that we are able
+	 * to separate concerns as in bpf_skb_store_bytes() should only
+	 * be the one responsible for writing buffers.
+	 *
+	 * It's really expected to be a slow path operation here for
+	 * control message replies, so we're implicitly linearizing,
+	 * uncloning and drop offloads from the skb by this.
+	 */
+	ret = __bpf_try_make_writable(skb, skb->len);
+	if (!ret) {
+		if (new_len > skb->len)
+			ret = bpf_skb_grow_rcsum(skb, new_len);
+		else if (new_len < skb->len)
+			ret = bpf_skb_trim_rcsum(skb, new_len);
+		if (!ret && skb_is_gso(skb))
+			skb_gso_reset(skb);
+	}
+
+	bpf_compute_data_end(skb);
+	return ret;
+}
+
+static const struct bpf_func_proto bpf_skb_change_tail_proto = {
+	.func		= bpf_skb_change_tail,
+	.gpl_only	= false,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_CTX,
+	.arg2_type	= ARG_ANYTHING,
+	.arg3_type	= ARG_ANYTHING,
+};
+
 bool bpf_helper_changes_skb_data(void *func)
 {
 	if (func == bpf_skb_vlan_push)
@@ -2002,6 +2092,8 @@ bool bpf_helper_changes_skb_data(void *func)
 		return true;
 	if (func == bpf_skb_change_proto)
 		return true;
+	if (func == bpf_skb_change_tail)
+		return true;
 	if (func == bpf_l3_csum_replace)
 		return true;
 	if (func == bpf_l4_csum_replace)
@@ -2282,7 +2374,6 @@ bpf_get_skb_set_tunnel_proto(enum bpf_func_id which)
 	}
 }
 
-#ifdef CONFIG_SOCK_CGROUP_DATA
 static u64 bpf_skb_under_cgroup(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
 {
 	struct sk_buff *skb = (struct sk_buff *)(long)r1;
@@ -2303,7 +2394,7 @@ static u64 bpf_skb_under_cgroup(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
 	if (unlikely(!cgrp))
 		return -EAGAIN;
 
-	return cgroup_is_descendant(sock_cgroup_ptr(&sk->sk_cgrp_data), cgrp);
+	return sk_under_cgroup_hierarchy(sk, cgrp);
 }
 
 static const struct bpf_func_proto bpf_skb_under_cgroup_proto = {
@@ -2314,7 +2405,41 @@ static const struct bpf_func_proto bpf_skb_under_cgroup_proto = {
 	.arg2_type	= ARG_CONST_MAP_PTR,
 	.arg3_type	= ARG_ANYTHING,
 };
-#endif
+
+static unsigned long bpf_xdp_copy(void *dst_buff, const void *src_buff,
+				  unsigned long off, unsigned long len)
+{
+	memcpy(dst_buff, src_buff + off, len);
+	return 0;
+}
+
+static u64 bpf_xdp_event_output(u64 r1, u64 r2, u64 flags, u64 r4,
+				u64 meta_size)
+{
+	struct xdp_buff *xdp = (struct xdp_buff *)(long) r1;
+	struct bpf_map *map = (struct bpf_map *)(long) r2;
+	u64 xdp_size = (flags & BPF_F_CTXLEN_MASK) >> 32;
+	void *meta = (void *)(long) r4;
+
+	if (unlikely(flags & ~(BPF_F_CTXLEN_MASK | BPF_F_INDEX_MASK)))
+		return -EINVAL;
+	if (unlikely(xdp_size > (unsigned long)(xdp->data_end - xdp->data)))
+		return -EFAULT;
+
+	return bpf_event_output(map, flags, meta, meta_size, xdp, xdp_size,
+				bpf_xdp_copy);
+}
+
+static const struct bpf_func_proto bpf_xdp_event_output_proto = {
+	.func		= bpf_xdp_event_output,
+	.gpl_only	= true,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_CTX,
+	.arg2_type	= ARG_CONST_MAP_PTR,
+	.arg3_type	= ARG_ANYTHING,
+	.arg4_type	= ARG_PTR_TO_STACK,
+	.arg5_type	= ARG_CONST_STACK_SIZE,
+};
 
 static const struct bpf_func_proto *
 sk_filter_func_proto(enum bpf_func_id func_id)
@@ -2368,6 +2493,8 @@ tc_cls_act_func_proto(enum bpf_func_id func_id)
 		return &bpf_skb_change_proto_proto;
 	case BPF_FUNC_skb_change_type:
 		return &bpf_skb_change_type_proto;
+	case BPF_FUNC_skb_change_tail:
+		return &bpf_skb_change_tail_proto;
 	case BPF_FUNC_skb_get_tunnel_key:
 		return &bpf_skb_get_tunnel_key_proto;
 	case BPF_FUNC_skb_set_tunnel_key:
@@ -2386,10 +2513,8 @@ tc_cls_act_func_proto(enum bpf_func_id func_id)
 		return &bpf_skb_event_output_proto;
 	case BPF_FUNC_get_smp_processor_id:
 		return &bpf_get_smp_processor_id_proto;
-#ifdef CONFIG_SOCK_CGROUP_DATA
 	case BPF_FUNC_skb_under_cgroup:
 		return &bpf_skb_under_cgroup_proto;
-#endif
 	default:
 		return sk_filter_func_proto(func_id);
 	}
@@ -2398,7 +2523,12 @@ tc_cls_act_func_proto(enum bpf_func_id func_id)
 static const struct bpf_func_proto *
 xdp_func_proto(enum bpf_func_id func_id)
 {
-	return sk_filter_func_proto(func_id);
+	switch (func_id) {
+	case BPF_FUNC_perf_event_output:
+		return &bpf_xdp_event_output_proto;
+	default:
+		return sk_filter_func_proto(func_id);
+	}
 }
 
 static bool __is_valid_access(int off, int size, enum bpf_access_type type)