Merge branch 'skbuff-struct-group'

Kees Cook says:

====================
skbuff: Switch structure bounds to struct_group()

This is a pair of patches to add struct_group() to struct sk_buff. The
first is needed to work around sparse-specific complaints, and is new
for v2. The second patch is the same as originally sent as v1.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/wireguard/queueing.h

@@ -79,9 +79,7 @@ static inline void wg_reset_packet(struct sk_buff *skb, bool encapsulating)
 	u8 sw_hash = skb->sw_hash;
 	u32 hash = skb->hash;
 	skb_scrub_packet(skb, true);
-	memset(&skb->headers_start, 0,
-	       offsetof(struct sk_buff, headers_end) -
-		       offsetof(struct sk_buff, headers_start));
+	memset(&skb->headers, 0, sizeof(skb->headers));
 	if (encapsulating) {
 		skb->l4_hash = l4_hash;
 		skb->sw_hash = sw_hash;

include/linux/skbuff.h

@@ -795,7 +795,7 @@ struct sk_buff {
 #else
 #define CLONED_MASK	1
 #endif
-#define CLONED_OFFSET()		offsetof(struct sk_buff, __cloned_offset)
+#define CLONED_OFFSET		offsetof(struct sk_buff, __cloned_offset)
 
 	/* private: */
 	__u8			__cloned_offset[0];
@@ -811,25 +811,15 @@ struct sk_buff {
 	__u8			active_extensions;
 #endif
 
-	/* fields enclosed in headers_start/headers_end are copied
+	/* Fields enclosed in headers group are copied
 	 * using a single memcpy() in __copy_skb_header()
 	 */
-	/* private: */
-	__u32			headers_start[0];
-	/* public: */
-
-/* if you move pkt_type around you also must adapt those constants */
-#ifdef __BIG_ENDIAN_BITFIELD
-#define PKT_TYPE_MAX	(7 << 5)
-#else
-#define PKT_TYPE_MAX	7
-#endif
-#define PKT_TYPE_OFFSET()	offsetof(struct sk_buff, __pkt_type_offset)
+	struct_group(headers,
 
 	/* private: */
 	__u8			__pkt_type_offset[0];
 	/* public: */
-	__u8			pkt_type:3;
+	__u8			pkt_type:3; /* see PKT_TYPE_MAX */
 	__u8			ignore_df:1;
 	__u8			nf_trace:1;
 	__u8			ip_summed:2;
@@ -845,16 +835,10 @@ struct sk_buff {
 	__u8			encap_hdr_csum:1;
 	__u8			csum_valid:1;
 
-#ifdef __BIG_ENDIAN_BITFIELD
-#define PKT_VLAN_PRESENT_BIT	7
-#else
-#define PKT_VLAN_PRESENT_BIT	0
-#endif
-#define PKT_VLAN_PRESENT_OFFSET()	offsetof(struct sk_buff, __pkt_vlan_present_offset)
 	/* private: */
 	__u8			__pkt_vlan_present_offset[0];
 	/* public: */
-	__u8			vlan_present:1;
+	__u8			vlan_present:1;	/* See PKT_VLAN_PRESENT_BIT */
 	__u8			csum_complete_sw:1;
 	__u8			csum_level:2;
 	__u8			csum_not_inet:1;
@@ -935,9 +919,7 @@ struct sk_buff {
 	u64			kcov_handle;
 #endif
 
-	/* private: */
-	__u32			headers_end[0];
-	/* public: */
+	); /* end headers group */
 
 	/* These elements must be at the end, see alloc_skb() for details.  */
 	sk_buff_data_t		tail;
@@ -953,6 +935,22 @@ struct sk_buff {
 #endif
 };
 
+/* if you move pkt_type around you also must adapt those constants */
+#ifdef __BIG_ENDIAN_BITFIELD
+#define PKT_TYPE_MAX	(7 << 5)
+#else
+#define PKT_TYPE_MAX	7
+#endif
+#define PKT_TYPE_OFFSET		offsetof(struct sk_buff, __pkt_type_offset)
+
+/* if you move pkt_vlan_present around you also must adapt these constants */
+#ifdef __BIG_ENDIAN_BITFIELD
+#define PKT_VLAN_PRESENT_BIT	7
+#else
+#define PKT_VLAN_PRESENT_BIT	0
+#endif
+#define PKT_VLAN_PRESENT_OFFSET	offsetof(struct sk_buff, __pkt_vlan_present_offset)
+
 #ifdef __KERNEL__
 /*
  *	Handling routines are only of interest to the kernel

net/core/filter.c

@@ -301,7 +301,7 @@ static u32 convert_skb_access(int skb_field, int dst_reg, int src_reg,
 		break;
 
 	case SKF_AD_PKTTYPE:
-		*insn++ = BPF_LDX_MEM(BPF_B, dst_reg, src_reg, PKT_TYPE_OFFSET());
+		*insn++ = BPF_LDX_MEM(BPF_B, dst_reg, src_reg, PKT_TYPE_OFFSET);
 		*insn++ = BPF_ALU32_IMM(BPF_AND, dst_reg, PKT_TYPE_MAX);
 #ifdef __BIG_ENDIAN_BITFIELD
 		*insn++ = BPF_ALU32_IMM(BPF_RSH, dst_reg, 5);
@@ -323,7 +323,7 @@ static u32 convert_skb_access(int skb_field, int dst_reg, int src_reg,
 				      offsetof(struct sk_buff, vlan_tci));
 		break;
 	case SKF_AD_VLAN_TAG_PRESENT:
-		*insn++ = BPF_LDX_MEM(BPF_B, dst_reg, src_reg, PKT_VLAN_PRESENT_OFFSET());
+		*insn++ = BPF_LDX_MEM(BPF_B, dst_reg, src_reg, PKT_VLAN_PRESENT_OFFSET);
 		if (PKT_VLAN_PRESENT_BIT)
 			*insn++ = BPF_ALU32_IMM(BPF_RSH, dst_reg, PKT_VLAN_PRESENT_BIT);
 		if (PKT_VLAN_PRESENT_BIT < 7)
@@ -8029,7 +8029,7 @@ static int bpf_unclone_prologue(struct bpf_insn *insn_buf, bool direct_write,
 	 * (Fast-path, otherwise approximation that we might be
 	 *  a clone, do the rest in helper.)
 	 */
-	*insn++ = BPF_LDX_MEM(BPF_B, BPF_REG_6, BPF_REG_1, CLONED_OFFSET());
+	*insn++ = BPF_LDX_MEM(BPF_B, BPF_REG_6, BPF_REG_1, CLONED_OFFSET);
 	*insn++ = BPF_ALU32_IMM(BPF_AND, BPF_REG_6, CLONED_MASK);
 	*insn++ = BPF_JMP_IMM(BPF_JEQ, BPF_REG_6, 0, 7);
 
@@ -8617,7 +8617,7 @@ static u32 bpf_convert_ctx_access(enum bpf_access_type type,
 	case offsetof(struct __sk_buff, pkt_type):
 		*target_size = 1;
 		*insn++ = BPF_LDX_MEM(BPF_B, si->dst_reg, si->src_reg,
-				      PKT_TYPE_OFFSET());
+				      PKT_TYPE_OFFSET);
 		*insn++ = BPF_ALU32_IMM(BPF_AND, si->dst_reg, PKT_TYPE_MAX);
 #ifdef __BIG_ENDIAN_BITFIELD
 		*insn++ = BPF_ALU32_IMM(BPF_RSH, si->dst_reg, 5);
@@ -8642,7 +8642,7 @@ static u32 bpf_convert_ctx_access(enum bpf_access_type type,
 	case offsetof(struct __sk_buff, vlan_present):
 		*target_size = 1;
 		*insn++ = BPF_LDX_MEM(BPF_B, si->dst_reg, si->src_reg,
-				      PKT_VLAN_PRESENT_OFFSET());
+				      PKT_VLAN_PRESENT_OFFSET);
 		if (PKT_VLAN_PRESENT_BIT)
 			*insn++ = BPF_ALU32_IMM(BPF_RSH, si->dst_reg, PKT_VLAN_PRESENT_BIT);
 		if (PKT_VLAN_PRESENT_BIT < 7)

net/core/skbuff.c

@@ -992,12 +992,10 @@ void napi_consume_skb(struct sk_buff *skb, int budget)
 }
 EXPORT_SYMBOL(napi_consume_skb);
 
-/* Make sure a field is enclosed inside headers_start/headers_end section */
+/* Make sure a field is contained by headers group */
 #define CHECK_SKB_FIELD(field) \
-	BUILD_BUG_ON(offsetof(struct sk_buff, field) <		\
-		     offsetof(struct sk_buff, headers_start));	\
-	BUILD_BUG_ON(offsetof(struct sk_buff, field) >		\
-		     offsetof(struct sk_buff, headers_end));	\
+	BUILD_BUG_ON(offsetof(struct sk_buff, field) !=		\
+		     offsetof(struct sk_buff, headers.field));	\
 
 static void __copy_skb_header(struct sk_buff *new, const struct sk_buff *old)
 {
@@ -1009,14 +1007,12 @@ static void __copy_skb_header(struct sk_buff *new, const struct sk_buff *old)
 	__skb_ext_copy(new, old);
 	__nf_copy(new, old, false);
 
-	/* Note : this field could be in headers_start/headers_end section
+	/* Note : this field could be in the headers group.
 	 * It is not yet because we do not want to have a 16 bit hole
 	 */
 	new->queue_mapping = old->queue_mapping;
 
-	memcpy(&new->headers_start, &old->headers_start,
-	       offsetof(struct sk_buff, headers_end) -
-	       offsetof(struct sk_buff, headers_start));
+	memcpy(&new->headers, &old->headers, sizeof(new->headers));
 	CHECK_SKB_FIELD(protocol);
 	CHECK_SKB_FIELD(csum);
 	CHECK_SKB_FIELD(hash);