Merge branch 'bpf-helper-improvements'

Daniel Borkmann says:

====================
BPF updates

This set contains various updates for eBPF, i.e. the addition of a
generic csum helper function and other misc bits that mostly improve
existing helpers and ease programming with eBPF on cls_bpf. For more
details, please see individual patches.

Set is rebased on top of http://patchwork.ozlabs.org/patch/584465/.
====================

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

include/linux/bpf.h

@@ -65,6 +65,7 @@ enum bpf_arg_type {
 	 */
 	ARG_PTR_TO_STACK,	/* any pointer to eBPF program stack */
 	ARG_CONST_STACK_SIZE,	/* number of bytes accessed from stack */
+	ARG_CONST_STACK_SIZE_OR_ZERO, /* number of bytes accessed from stack or 0 */
 
 	ARG_PTR_TO_CTX,		/* pointer to context */
 	ARG_ANYTHING,		/* any (initialized) argument is ok */

include/linux/skbuff.h

@@ -2630,6 +2630,13 @@ static inline int skb_clone_writable(const struct sk_buff *skb, unsigned int len
 	       skb_headroom(skb) + len <= skb->hdr_len;
 }
 
+static inline int skb_try_make_writable(struct sk_buff *skb,
+					unsigned int write_len)
+{
+	return skb_cloned(skb) && !skb_clone_writable(skb, write_len) &&
+	       pskb_expand_head(skb, 0, 0, GFP_ATOMIC);
+}
+
 static inline int __skb_cow(struct sk_buff *skb, unsigned int headroom,
 			    int cloned)
 {

include/uapi/linux/bpf.h

@@ -287,6 +287,17 @@ enum bpf_func_id {
 	 * Return: >= 0 stackid on success or negative error
 	 */
 	BPF_FUNC_get_stackid,
+
+	/**
+	 * bpf_csum_diff(from, from_size, to, to_size, seed) - calculate csum diff
+	 * @from: raw from buffer
+	 * @from_size: length of from buffer
+	 * @to: raw to buffer
+	 * @to_size: length of to buffer
+	 * @seed: optional seed
+	 * Return: csum result
+	 */
+	BPF_FUNC_csum_diff,
 	__BPF_FUNC_MAX_ID,
 };
 
@@ -302,6 +313,7 @@ enum bpf_func_id {
 
 /* BPF_FUNC_l4_csum_replace flags. */
 #define BPF_F_PSEUDO_HDR		(1ULL << 4)
+#define BPF_F_MARK_MANGLED_0		(1ULL << 5)
 
 /* BPF_FUNC_clone_redirect and BPF_FUNC_redirect flags. */
 #define BPF_F_INGRESS			(1ULL << 0)

kernel/bpf/verifier.c

@@ -779,15 +779,24 @@ static int check_xadd(struct verifier_env *env, struct bpf_insn *insn)
  * bytes from that pointer, make sure that it's within stack boundary
  * and all elements of stack are initialized
  */
-static int check_stack_boundary(struct verifier_env *env,
-				int regno, int access_size)
+static int check_stack_boundary(struct verifier_env *env, int regno,
+				int access_size, bool zero_size_allowed)
 {
 	struct verifier_state *state = &env->cur_state;
 	struct reg_state *regs = state->regs;
 	int off, i;
 
-	if (regs[regno].type != PTR_TO_STACK)
+	if (regs[regno].type != PTR_TO_STACK) {
+		if (zero_size_allowed && access_size == 0 &&
+		    regs[regno].type == CONST_IMM &&
+		    regs[regno].imm  == 0)
+			return 0;
+
+		verbose("R%d type=%s expected=%s\n", regno,
+			reg_type_str[regs[regno].type],
+			reg_type_str[PTR_TO_STACK]);
 		return -EACCES;
+	}
 
 	off = regs[regno].imm;
 	if (off >= 0 || off < -MAX_BPF_STACK || off + access_size > 0 ||
@@ -830,15 +839,24 @@ static int check_func_arg(struct verifier_env *env, u32 regno,
 		return 0;
 	}
 
-	if (arg_type == ARG_PTR_TO_STACK || arg_type == ARG_PTR_TO_MAP_KEY ||
+	if (arg_type == ARG_PTR_TO_MAP_KEY ||
 	    arg_type == ARG_PTR_TO_MAP_VALUE) {
 		expected_type = PTR_TO_STACK;
-	} else if (arg_type == ARG_CONST_STACK_SIZE) {
+	} else if (arg_type == ARG_CONST_STACK_SIZE ||
+		   arg_type == ARG_CONST_STACK_SIZE_OR_ZERO) {
 		expected_type = CONST_IMM;
 	} else if (arg_type == ARG_CONST_MAP_PTR) {
 		expected_type = CONST_PTR_TO_MAP;
 	} else if (arg_type == ARG_PTR_TO_CTX) {
 		expected_type = PTR_TO_CTX;
+	} else if (arg_type == ARG_PTR_TO_STACK) {
+		expected_type = PTR_TO_STACK;
+		/* One exception here. In case function allows for NULL to be
+		 * passed in as argument, it's a CONST_IMM type. Final test
+		 * happens during stack boundary checking.
+		 */
+		if (reg->type == CONST_IMM && reg->imm == 0)
+			expected_type = CONST_IMM;
 	} else {
 		verbose("unsupported arg_type %d\n", arg_type);
 		return -EFAULT;
@@ -868,8 +886,8 @@ static int check_func_arg(struct verifier_env *env, u32 regno,
 			verbose("invalid map_ptr to access map->key\n");
 			return -EACCES;
 		}
-		err = check_stack_boundary(env, regno, (*mapp)->key_size);
-
+		err = check_stack_boundary(env, regno, (*mapp)->key_size,
+					   false);
 	} else if (arg_type == ARG_PTR_TO_MAP_VALUE) {
 		/* bpf_map_xxx(..., map_ptr, ..., value) call:
 		 * check [value, value + map->value_size) validity
@@ -879,9 +897,12 @@ static int check_func_arg(struct verifier_env *env, u32 regno,
 			verbose("invalid map_ptr to access map->value\n");
 			return -EACCES;
 		}
-		err = check_stack_boundary(env, regno, (*mapp)->value_size);
+		err = check_stack_boundary(env, regno, (*mapp)->value_size,
+					   false);
+	} else if (arg_type == ARG_CONST_STACK_SIZE ||
+		   arg_type == ARG_CONST_STACK_SIZE_OR_ZERO) {
+		bool zero_size_allowed = (arg_type == ARG_CONST_STACK_SIZE_OR_ZERO);
 
-	} else if (arg_type == ARG_CONST_STACK_SIZE) {
 		/* bpf_xxx(..., buf, len) call will access 'len' bytes
 		 * from stack pointer 'buf'. Check it
 		 * note: regno == len, regno - 1 == buf
@@ -891,7 +912,8 @@ static int check_func_arg(struct verifier_env *env, u32 regno,
 			verbose("ARG_CONST_STACK_SIZE cannot be first argument\n");
 			return -EACCES;
 		}
-		err = check_stack_boundary(env, regno - 1, reg->imm);
+		err = check_stack_boundary(env, regno - 1, reg->imm,
+					   zero_size_allowed);
 	}
 
 	return err;

net/core/filter.c

@@ -530,12 +530,14 @@ static int bpf_convert_filter(struct sock_filter *prog, int len,
 			*insn = BPF_MOV64_REG(BPF_REG_A, BPF_REG_TMP);
 			break;
 
-		/* RET_K, RET_A are remaped into 2 insns. */
+		/* RET_K is remaped into 2 insns. RET_A case doesn't need an
+		 * extra mov as BPF_REG_0 is already mapped into BPF_REG_A.
+		 */
 		case BPF_RET | BPF_A:
 		case BPF_RET | BPF_K:
-			*insn++ = BPF_MOV32_RAW(BPF_RVAL(fp->code) == BPF_K ?
-						BPF_K : BPF_X, BPF_REG_0,
-						BPF_REG_A, fp->k);
+			if (BPF_RVAL(fp->code) == BPF_K)
+				*insn++ = BPF_MOV32_RAW(BPF_K, BPF_REG_0,
+							0, fp->k);
 			*insn = BPF_EXIT_INSN();
 			break;
 
@@ -1333,15 +1335,22 @@ int sk_reuseport_attach_bpf(u32 ufd, struct sock *sk)
 	return 0;
 }
 
-#define BPF_LDST_LEN 16U
+struct bpf_scratchpad {
+	union {
+		__be32 diff[MAX_BPF_STACK / sizeof(__be32)];
+		u8     buff[MAX_BPF_STACK];
+	};
+};
+
+static DEFINE_PER_CPU(struct bpf_scratchpad, bpf_sp);
 
 static u64 bpf_skb_store_bytes(u64 r1, u64 r2, u64 r3, u64 r4, u64 flags)
 {
+	struct bpf_scratchpad *sp = this_cpu_ptr(&bpf_sp);
 	struct sk_buff *skb = (struct sk_buff *) (long) r1;
 	int offset = (int) r2;
 	void *from = (void *) (long) r3;
 	unsigned int len = (unsigned int) r4;
-	char buf[BPF_LDST_LEN];
 	void *ptr;
 
 	if (unlikely(flags & ~(BPF_F_RECOMPUTE_CSUM)))
@@ -1355,14 +1364,12 @@ static u64 bpf_skb_store_bytes(u64 r1, u64 r2, u64 r3, u64 r4, u64 flags)
 	 *
 	 * so check for invalid 'offset' and too large 'len'
 	 */
-	if (unlikely((u32) offset > 0xffff || len > sizeof(buf)))
+	if (unlikely((u32) offset > 0xffff || len > sizeof(sp->buff)))
 		return -EFAULT;
-
-	if (unlikely(skb_cloned(skb) &&
-		     !skb_clone_writable(skb, offset + len)))
+	if (unlikely(skb_try_make_writable(skb, offset + len)))
 		return -EFAULT;
 
-	ptr = skb_header_pointer(skb, offset, len, buf);
+	ptr = skb_header_pointer(skb, offset, len, sp->buff);
 	if (unlikely(!ptr))
 		return -EFAULT;
 
@@ -1371,7 +1378,7 @@ static u64 bpf_skb_store_bytes(u64 r1, u64 r2, u64 r3, u64 r4, u64 flags)
 
 	memcpy(ptr, from, len);
 
-	if (ptr == buf)
+	if (ptr == sp->buff)
 		/* skb_store_bits cannot return -EFAULT here */
 		skb_store_bits(skb, offset, ptr, len);
 
@@ -1400,7 +1407,7 @@ static u64 bpf_skb_load_bytes(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
 	unsigned int len = (unsigned int) r4;
 	void *ptr;
 
-	if (unlikely((u32) offset > 0xffff || len > BPF_LDST_LEN))
+	if (unlikely((u32) offset > 0xffff || len > MAX_BPF_STACK))
 		return -EFAULT;
 
 	ptr = skb_header_pointer(skb, offset, len, to);
@@ -1432,9 +1439,7 @@ static u64 bpf_l3_csum_replace(u64 r1, u64 r2, u64 from, u64 to, u64 flags)
 		return -EINVAL;
 	if (unlikely((u32) offset > 0xffff))
 		return -EFAULT;
-
-	if (unlikely(skb_cloned(skb) &&
-		     !skb_clone_writable(skb, offset + sizeof(sum))))
+	if (unlikely(skb_try_make_writable(skb, offset + sizeof(sum))))
 		return -EFAULT;
 
 	ptr = skb_header_pointer(skb, offset, sizeof(sum), &sum);
@@ -1474,23 +1479,31 @@ static u64 bpf_l4_csum_replace(u64 r1, u64 r2, u64 from, u64 to, u64 flags)
 {
 	struct sk_buff *skb = (struct sk_buff *) (long) r1;
 	bool is_pseudo = flags & BPF_F_PSEUDO_HDR;
+	bool is_mmzero = flags & BPF_F_MARK_MANGLED_0;
 	int offset = (int) r2;
 	__sum16 sum, *ptr;
 
-	if (unlikely(flags & ~(BPF_F_PSEUDO_HDR | BPF_F_HDR_FIELD_MASK)))
+	if (unlikely(flags & ~(BPF_F_MARK_MANGLED_0 | BPF_F_PSEUDO_HDR |
+			       BPF_F_HDR_FIELD_MASK)))
 		return -EINVAL;
 	if (unlikely((u32) offset > 0xffff))
 		return -EFAULT;
-
-	if (unlikely(skb_cloned(skb) &&
-		     !skb_clone_writable(skb, offset + sizeof(sum))))
+	if (unlikely(skb_try_make_writable(skb, offset + sizeof(sum))))
 		return -EFAULT;
 
 	ptr = skb_header_pointer(skb, offset, sizeof(sum), &sum);
 	if (unlikely(!ptr))
 		return -EFAULT;
+	if (is_mmzero && !*ptr)
+		return 0;
 
 	switch (flags & BPF_F_HDR_FIELD_MASK) {
+	case 0:
+		if (unlikely(from != 0))
+			return -EINVAL;
+
+		inet_proto_csum_replace_by_diff(ptr, skb, to, is_pseudo);
+		break;
 	case 2:
 		inet_proto_csum_replace2(ptr, skb, from, to, is_pseudo);
 		break;
@@ -1501,6 +1514,8 @@ static u64 bpf_l4_csum_replace(u64 r1, u64 r2, u64 from, u64 to, u64 flags)
 		return -EINVAL;
 	}
 
+	if (is_mmzero && !*ptr)
+		*ptr = CSUM_MANGLED_0;
 	if (ptr == &sum)
 		/* skb_store_bits guaranteed to not return -EFAULT here */
 		skb_store_bits(skb, offset, ptr, sizeof(sum));
@@ -1519,6 +1534,45 @@ const struct bpf_func_proto bpf_l4_csum_replace_proto = {
 	.arg5_type	= ARG_ANYTHING,
 };
 
+static u64 bpf_csum_diff(u64 r1, u64 from_size, u64 r3, u64 to_size, u64 seed)
+{
+	struct bpf_scratchpad *sp = this_cpu_ptr(&bpf_sp);
+	u64 diff_size = from_size + to_size;
+	__be32 *from = (__be32 *) (long) r1;
+	__be32 *to   = (__be32 *) (long) r3;
+	int i, j = 0;
+
+	/* This is quite flexible, some examples:
+	 *
+	 * from_size == 0, to_size > 0,  seed := csum --> pushing data
+	 * from_size > 0,  to_size == 0, seed := csum --> pulling data
+	 * from_size > 0,  to_size > 0,  seed := 0    --> diffing data
+	 *
+	 * Even for diffing, from_size and to_size don't need to be equal.
+	 */
+	if (unlikely(((from_size | to_size) & (sizeof(__be32) - 1)) ||
+		     diff_size > sizeof(sp->diff)))
+		return -EINVAL;
+
+	for (i = 0; i < from_size / sizeof(__be32); i++, j++)
+		sp->diff[j] = ~from[i];
+	for (i = 0; i <   to_size / sizeof(__be32); i++, j++)
+		sp->diff[j] = to[i];
+
+	return csum_partial(sp->diff, diff_size, seed);
+}
+
+const struct bpf_func_proto bpf_csum_diff_proto = {
+	.func		= bpf_csum_diff,
+	.gpl_only	= false,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_STACK,
+	.arg2_type	= ARG_CONST_STACK_SIZE_OR_ZERO,
+	.arg3_type	= ARG_PTR_TO_STACK,
+	.arg4_type	= ARG_CONST_STACK_SIZE_OR_ZERO,
+	.arg5_type	= ARG_ANYTHING,
+};
+
 static u64 bpf_clone_redirect(u64 r1, u64 ifindex, u64 flags, u64 r4, u64 r5)
 {
 	struct sk_buff *skb = (struct sk_buff *) (long) r1, *skb2;
@@ -1682,6 +1736,13 @@ bool bpf_helper_changes_skb_data(void *func)
 		return true;
 	if (func == bpf_skb_vlan_pop)
 		return true;
+	if (func == bpf_skb_store_bytes)
+		return true;
+	if (func == bpf_l3_csum_replace)
+		return true;
+	if (func == bpf_l4_csum_replace)
+		return true;
+
 	return false;
 }
 
@@ -1849,6 +1910,8 @@ tc_cls_act_func_proto(enum bpf_func_id func_id)
 		return &bpf_skb_store_bytes_proto;
 	case BPF_FUNC_skb_load_bytes:
 		return &bpf_skb_load_bytes_proto;
+	case BPF_FUNC_csum_diff:
+		return &bpf_csum_diff_proto;
 	case BPF_FUNC_l3_csum_replace:
 		return &bpf_l3_csum_replace_proto;
 	case BPF_FUNC_l4_csum_replace:

net/sched/act_csum.c

@@ -105,9 +105,7 @@ static void *tcf_csum_skb_nextlayer(struct sk_buff *skb,
 	int hl = ihl + jhl;
 
 	if (!pskb_may_pull(skb, ipl + ntkoff) || (ipl < hl) ||
-	    (skb_cloned(skb) &&
-	     !skb_clone_writable(skb, hl + ntkoff) &&
-	     pskb_expand_head(skb, 0, 0, GFP_ATOMIC)))
+	    skb_try_make_writable(skb, hl + ntkoff))
 		return NULL;
 	else
 		return (void *)(skb_network_header(skb) + ihl);
@@ -365,9 +363,7 @@ static int tcf_csum_ipv4(struct sk_buff *skb, u32 update_flags)
 	}
 
 	if (update_flags & TCA_CSUM_UPDATE_FLAG_IPV4HDR) {
-		if (skb_cloned(skb) &&
-		    !skb_clone_writable(skb, sizeof(*iph) + ntkoff) &&
-		    pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
+		if (skb_try_make_writable(skb, sizeof(*iph) + ntkoff))
 			goto fail;
 
 		ip_send_check(ip_hdr(skb));