Merge branch 'netlink-validation-improvements-refactoring'

Johannes Berg says:

====================
netlink validation improvements/refactoring

Alright, this is the resend now, really just changing

 - the WARN_ON_ONCE() as spotted by Jakub;
 - mark the export patch no longer RFC.
   I wasn't actually sure if you meant this one too, and I really
   should dig out and polish the code that showed it in userspace.
====================

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

12 files changed, 821 insertions, 173 deletions

diff --git a/include/net/netlink.h b/include/net/netlink.h
index 67c57d6942e3..c0411f14fb53 100644
--- a/include/net/netlink.h
+++ b/include/net/netlink.h
@@ -182,19 +182,28 @@ enum {
 	NLA_BITFIELD32,
 	NLA_REJECT,
 	NLA_EXACT_LEN,
-	NLA_EXACT_LEN_WARN,
 	NLA_MIN_LEN,
 	__NLA_TYPE_MAX,
 };
 
 #define NLA_TYPE_MAX (__NLA_TYPE_MAX - 1)
 
+struct netlink_range_validation {
+	u64 min, max;
+};
+
+struct netlink_range_validation_signed {
+	s64 min, max;
+};
+
 enum nla_policy_validation {
 	NLA_VALIDATE_NONE,
 	NLA_VALIDATE_RANGE,
 	NLA_VALIDATE_MIN,
 	NLA_VALIDATE_MAX,
+	NLA_VALIDATE_RANGE_PTR,
 	NLA_VALIDATE_FUNCTION,
+	NLA_VALIDATE_WARN_TOO_LONG,
 };
 
 /**
@@ -217,7 +226,7 @@ enum nla_policy_validation {
  *    NLA_NESTED,
  *    NLA_NESTED_ARRAY     Length verification is done by checking len of
  *                         nested header (or empty); len field is used if
- *                         validation_data is also used, for the max attr
+ *                         nested_policy is also used, for the max attr
  *                         number in the nested policy.
  *    NLA_U8, NLA_U16,
  *    NLA_U32, NLA_U64,
@@ -228,34 +237,32 @@ enum nla_policy_validation {
  *                         just like "All other"
  *    NLA_BITFIELD32       Unused
  *    NLA_REJECT           Unused
- *    NLA_EXACT_LEN        Attribute must have exactly this length, otherwise
- *                         it is rejected.
- *    NLA_EXACT_LEN_WARN   Attribute should have exactly this length, a warning
- *                         is logged if it is longer, shorter is rejected.
+ *    NLA_EXACT_LEN        Attribute should have exactly this length, otherwise
+ *                         it is rejected or warned about, the latter happening
+ *                         if and only if the `validation_type' is set to
+ *                         NLA_VALIDATE_WARN_TOO_LONG.
  *    NLA_MIN_LEN          Minimum length of attribute payload
  *    All other            Minimum length of attribute payload
  *
- * Meaning of `validation_data' field:
+ * Meaning of validation union:
  *    NLA_BITFIELD32       This is a 32-bit bitmap/bitselector attribute and
- *                         validation data must point to a u32 value of valid
- *                         flags
- *    NLA_REJECT           This attribute is always rejected and validation data
+ *                         `bitfield32_valid' is the u32 value of valid flags
+ *    NLA_REJECT           This attribute is always rejected and `reject_message'
  *                         may point to a string to report as the error instead
  *                         of the generic one in extended ACK.
- *    NLA_NESTED           Points to a nested policy to validate, must also set
- *                         `len' to the max attribute number.
+ *    NLA_NESTED           `nested_policy' to a nested policy to validate, must
+ *                         also set `len' to the max attribute number. Use the
+ *                         provided NLA_POLICY_NESTED() macro.
  *                         Note that nla_parse() will validate, but of course not
  *                         parse, the nested sub-policies.
- *    NLA_NESTED_ARRAY     Points to a nested policy to validate, must also set
- *                         `len' to the max attribute number. The difference to
- *                         NLA_NESTED is the structure - NLA_NESTED has the
- *                         nested attributes directly inside, while an array has
- *                         the nested attributes at another level down and the
- *                         attributes directly in the nesting don't matter.
- *    All other            Unused - but note that it's a union
- *
- * Meaning of `min' and `max' fields, use via NLA_POLICY_MIN, NLA_POLICY_MAX
- * and NLA_POLICY_RANGE:
+ *    NLA_NESTED_ARRAY     `nested_policy' points to a nested policy to validate,
+ *                         must also set `len' to the max attribute number. Use
+ *                         the provided NLA_POLICY_NESTED_ARRAY() macro.
+ *                         The difference to NLA_NESTED is the structure:
+ *                         NLA_NESTED has the nested attributes directly inside
+ *                         while an array has the nested attributes at another
+ *                         level down and the attribute types directly in the
+ *                         nesting don't matter.
  *    NLA_U8,
  *    NLA_U16,
  *    NLA_U32,
@@ -263,29 +270,47 @@ enum nla_policy_validation {
  *    NLA_S8,
  *    NLA_S16,
  *    NLA_S32,
- *    NLA_S64              These are used depending on the validation_type
- *                         field, if that is min/max/range then the minimum,
- *                         maximum and both are used (respectively) to check
+ *    NLA_S64              The `min' and `max' fields are used depending on the
+ *                         validation_type field, if that is min/max/range then
+ *                         the min, max or both are used (respectively) to check
  *                         the value of the integer attribute.
  *                         Note that in the interest of code simplicity and
  *                         struct size both limits are s16, so you cannot
  *                         enforce a range that doesn't fall within the range
  *                         of s16 - do that as usual in the code instead.
+ *                         Use the NLA_POLICY_MIN(), NLA_POLICY_MAX() and
+ *                         NLA_POLICY_RANGE() macros.
+ *    NLA_U8,
+ *    NLA_U16,
+ *    NLA_U32,
+ *    NLA_U64              If the validation_type field instead is set to
+ *                         NLA_VALIDATE_RANGE_PTR, `range' must be a pointer
+ *                         to a struct netlink_range_validation that indicates
+ *                         the min/max values.
+ *                         Use NLA_POLICY_FULL_RANGE().
+ *    NLA_S8,
+ *    NLA_S16,
+ *    NLA_S32,
+ *    NLA_S64              If the validation_type field instead is set to
+ *                         NLA_VALIDATE_RANGE_PTR, `range_signed' must be a
+ *                         pointer to a struct netlink_range_validation_signed
+ *                         that indicates the min/max values.
+ *                         Use NLA_POLICY_FULL_RANGE_SIGNED().
  *    All other            Unused - but note that it's a union
  *
  * Meaning of `validate' field, use via NLA_POLICY_VALIDATE_FN:
- *    NLA_BINARY           Validation function called for the attribute,
- *                         not compatible with use of the validation_data
- *                         as in NLA_BITFIELD32, NLA_REJECT, NLA_NESTED and
- *                         NLA_NESTED_ARRAY.
+ *    NLA_BINARY           Validation function called for the attribute.
  *    All other            Unused - but note that it's a union
  *
  * Example:
+ *
+ * static const u32 myvalidflags = 0xff231023;
+ *
  * static const struct nla_policy my_policy[ATTR_MAX+1] = {
  * 	[ATTR_FOO] = { .type = NLA_U16 },
  *	[ATTR_BAR] = { .type = NLA_STRING, .len = BARSIZ },
  *	[ATTR_BAZ] = { .type = NLA_EXACT_LEN, .len = sizeof(struct mystruct) },
- *	[ATTR_GOO] = { .type = NLA_BITFIELD32, .validation_data = &myvalidflags },
+ *	[ATTR_GOO] = NLA_POLICY_BITFIELD32(myvalidflags),
  * };
  */
 struct nla_policy {
@@ -293,7 +318,11 @@ struct nla_policy {
 	u8		validation_type;
 	u16		len;
 	union {
-		const void *validation_data;
+		const u32 bitfield32_valid;
+		const char *reject_message;
+		const struct nla_policy *nested_policy;
+		struct netlink_range_validation *range;
+		struct netlink_range_validation_signed *range_signed;
 		struct {
 			s16 min, max;
 		};
@@ -321,28 +350,39 @@ struct nla_policy {
 };
 
 #define NLA_POLICY_EXACT_LEN(_len)	{ .type = NLA_EXACT_LEN, .len = _len }
-#define NLA_POLICY_EXACT_LEN_WARN(_len)	{ .type = NLA_EXACT_LEN_WARN, \
-					  .len = _len }
+#define NLA_POLICY_EXACT_LEN_WARN(_len) \
+	{ .type = NLA_EXACT_LEN, .len = _len, \
+	  .validation_type = NLA_VALIDATE_WARN_TOO_LONG, }
 #define NLA_POLICY_MIN_LEN(_len)	{ .type = NLA_MIN_LEN, .len = _len }
 
 #define NLA_POLICY_ETH_ADDR		NLA_POLICY_EXACT_LEN(ETH_ALEN)
 #define NLA_POLICY_ETH_ADDR_COMPAT	NLA_POLICY_EXACT_LEN_WARN(ETH_ALEN)
 
 #define _NLA_POLICY_NESTED(maxattr, policy) \
-	{ .type = NLA_NESTED, .validation_data = policy, .len = maxattr }
+	{ .type = NLA_NESTED, .nested_policy = policy, .len = maxattr }
 #define _NLA_POLICY_NESTED_ARRAY(maxattr, policy) \
-	{ .type = NLA_NESTED_ARRAY, .validation_data = policy, .len = maxattr }
+	{ .type = NLA_NESTED_ARRAY, .nested_policy = policy, .len = maxattr }
 #define NLA_POLICY_NESTED(policy) \
 	_NLA_POLICY_NESTED(ARRAY_SIZE(policy) - 1, policy)
 #define NLA_POLICY_NESTED_ARRAY(policy) \
 	_NLA_POLICY_NESTED_ARRAY(ARRAY_SIZE(policy) - 1, policy)
+#define NLA_POLICY_BITFIELD32(valid) \
+	{ .type = NLA_BITFIELD32, .bitfield32_valid = valid }
 
 #define __NLA_ENSURE(condition) BUILD_BUG_ON_ZERO(!(condition))
+#define NLA_ENSURE_UINT_TYPE(tp)			\
+	(__NLA_ENSURE(tp == NLA_U8 || tp == NLA_U16 ||	\
+		      tp == NLA_U32 || tp == NLA_U64 ||	\
+		      tp == NLA_MSECS) + tp)
+#define NLA_ENSURE_SINT_TYPE(tp)			\
+	(__NLA_ENSURE(tp == NLA_S8 || tp == NLA_S16  ||	\
+		      tp == NLA_S32 || tp == NLA_S64) + tp)
 #define NLA_ENSURE_INT_TYPE(tp)				\
 	(__NLA_ENSURE(tp == NLA_S8 || tp == NLA_U8 ||	\
 		      tp == NLA_S16 || tp == NLA_U16 ||	\
 		      tp == NLA_S32 || tp == NLA_U32 ||	\
-		      tp == NLA_S64 || tp == NLA_U64) + tp)
+		      tp == NLA_S64 || tp == NLA_U64 ||	\
+		      tp == NLA_MSECS) + tp)
 #define NLA_ENSURE_NO_VALIDATION_PTR(tp)		\
 	(__NLA_ENSURE(tp != NLA_BITFIELD32 &&		\
 		      tp != NLA_REJECT &&		\
@@ -356,6 +396,18 @@ struct nla_policy {
 	.max = _max					\
 }
 
+#define NLA_POLICY_FULL_RANGE(tp, _range) {		\
+	.type = NLA_ENSURE_UINT_TYPE(tp),		\
+	.validation_type = NLA_VALIDATE_RANGE_PTR,	\
+	.range = _range,				\
+}
+
+#define NLA_POLICY_FULL_RANGE_SIGNED(tp, _range) {	\
+	.type = NLA_ENSURE_SINT_TYPE(tp),		\
+	.validation_type = NLA_VALIDATE_RANGE_PTR,	\
+	.range_signed = _range,				\
+}
+
 #define NLA_POLICY_MIN(tp, _min) {			\
 	.type = NLA_ENSURE_INT_TYPE(tp),		\
 	.validation_type = NLA_VALIDATE_MIN,		\
@@ -1876,4 +1928,15 @@ static inline bool nla_is_last(const struct nlattr *nla, int rem)
 	return nla->nla_len == rem;
 }
 
+void nla_get_range_unsigned(const struct nla_policy *pt,
+			    struct netlink_range_validation *range);
+void nla_get_range_signed(const struct nla_policy *pt,
+			  struct netlink_range_validation_signed *range);
+
+int netlink_policy_dump_start(const struct nla_policy *policy,
+			      unsigned int maxtype,
+			      unsigned long *state);
+bool netlink_policy_dump_loop(unsigned long *state);
+int netlink_policy_dump_write(struct sk_buff *skb, unsigned long state);
+
 #endif
diff --git a/include/uapi/linux/genetlink.h b/include/uapi/linux/genetlink.h
index 877f7fa95466..9c0636ec2286 100644
--- a/include/uapi/linux/genetlink.h
+++ b/include/uapi/linux/genetlink.h
@@ -48,6 +48,7 @@ enum {
 	CTRL_CMD_NEWMCAST_GRP,
 	CTRL_CMD_DELMCAST_GRP,
 	CTRL_CMD_GETMCAST_GRP, /* unused */
+	CTRL_CMD_GETPOLICY,
 	__CTRL_CMD_MAX,
 };
 
@@ -62,6 +63,7 @@ enum {
 	CTRL_ATTR_MAXATTR,
 	CTRL_ATTR_OPS,
 	CTRL_ATTR_MCAST_GROUPS,
+	CTRL_ATTR_POLICY,
 	__CTRL_ATTR_MAX,
 };
 
diff --git a/include/uapi/linux/netlink.h b/include/uapi/linux/netlink.h
index 0a4d73317759..eac8a6a648ea 100644
--- a/include/uapi/linux/netlink.h
+++ b/include/uapi/linux/netlink.h
@@ -249,4 +249,107 @@ struct nla_bitfield32 {
 	__u32 selector;
 };
 
+/*
+ * policy descriptions - it's specific to each family how this is used
+ * Normally, it should be retrieved via a dump inside another attribute
+ * specifying where it applies.
+ */
+
+/**
+ * enum netlink_attribute_type - type of an attribute
+ * @NL_ATTR_TYPE_INVALID: unused
+ * @NL_ATTR_TYPE_FLAG: flag attribute (present/not present)
+ * @NL_ATTR_TYPE_U8: 8-bit unsigned attribute
+ * @NL_ATTR_TYPE_U16: 16-bit unsigned attribute
+ * @NL_ATTR_TYPE_U32: 32-bit unsigned attribute
+ * @NL_ATTR_TYPE_U64: 64-bit unsigned attribute
+ * @NL_ATTR_TYPE_S8: 8-bit signed attribute
+ * @NL_ATTR_TYPE_S16: 16-bit signed attribute
+ * @NL_ATTR_TYPE_S32: 32-bit signed attribute
+ * @NL_ATTR_TYPE_S64: 64-bit signed attribute
+ * @NL_ATTR_TYPE_BINARY: binary data, min/max length may be specified
+ * @NL_ATTR_TYPE_STRING: string, min/max length may be specified
+ * @NL_ATTR_TYPE_NUL_STRING: NUL-terminated string,
+ *	min/max length may be specified
+ * @NL_ATTR_TYPE_NESTED: nested, i.e. the content of this attribute
+ *	consists of sub-attributes. The nested policy and maxtype
+ *	inside may be specified.
+ * @NL_ATTR_TYPE_NESTED_ARRAY: nested array, i.e. the content of this
+ *	attribute contains sub-attributes whose type is irrelevant
+ *	(just used to separate the array entries) and each such array
+ *	entry has attributes again, the policy for those inner ones
+ *	and the corresponding maxtype may be specified.
+ * @NL_ATTR_TYPE_BITFIELD32: &struct nla_bitfield32 attribute
+ */
+enum netlink_attribute_type {
+	NL_ATTR_TYPE_INVALID,
+
+	NL_ATTR_TYPE_FLAG,
+
+	NL_ATTR_TYPE_U8,
+	NL_ATTR_TYPE_U16,
+	NL_ATTR_TYPE_U32,
+	NL_ATTR_TYPE_U64,
+
+	NL_ATTR_TYPE_S8,
+	NL_ATTR_TYPE_S16,
+	NL_ATTR_TYPE_S32,
+	NL_ATTR_TYPE_S64,
+
+	NL_ATTR_TYPE_BINARY,
+	NL_ATTR_TYPE_STRING,
+	NL_ATTR_TYPE_NUL_STRING,
+
+	NL_ATTR_TYPE_NESTED,
+	NL_ATTR_TYPE_NESTED_ARRAY,
+
+	NL_ATTR_TYPE_BITFIELD32,
+};
+
+/**
+ * enum netlink_policy_type_attr - policy type attributes
+ * @NL_POLICY_TYPE_ATTR_UNSPEC: unused
+ * @NL_POLICY_TYPE_ATTR_TYPE: type of the attribute,
+ *	&enum netlink_attribute_type (U32)
+ * @NL_POLICY_TYPE_ATTR_MIN_VALUE_S: minimum value for signed
+ *	integers (S64)
+ * @NL_POLICY_TYPE_ATTR_MAX_VALUE_S: maximum value for signed
+ *	integers (S64)
+ * @NL_POLICY_TYPE_ATTR_MIN_VALUE_U: minimum value for unsigned
+ *	integers (U64)
+ * @NL_POLICY_TYPE_ATTR_MAX_VALUE_U: maximum value for unsigned
+ *	integers (U64)
+ * @NL_POLICY_TYPE_ATTR_MIN_LENGTH: minimum length for binary
+ *	attributes, no minimum if not given (U32)
+ * @NL_POLICY_TYPE_ATTR_MAX_LENGTH: maximum length for binary
+ *	attributes, no maximum if not given (U32)
+ * @NL_POLICY_TYPE_ATTR_POLICY_IDX: sub policy for nested and
+ *	nested array types (U32)
+ * @NL_POLICY_TYPE_ATTR_POLICY_MAXTYPE: maximum sub policy
+ *	attribute for nested and nested array types, this can
+ *	in theory be < the size of the policy pointed to by
+ *	the index, if limited inside the nesting (U32)
+ * @NL_POLICY_TYPE_ATTR_BITFIELD32_MASK: valid mask for the
+ *	bitfield32 type (U32)
+ * @NL_POLICY_TYPE_ATTR_PAD: pad attribute for 64-bit alignment
+ */
+enum netlink_policy_type_attr {
+	NL_POLICY_TYPE_ATTR_UNSPEC,
+	NL_POLICY_TYPE_ATTR_TYPE,
+	NL_POLICY_TYPE_ATTR_MIN_VALUE_S,
+	NL_POLICY_TYPE_ATTR_MAX_VALUE_S,
+	NL_POLICY_TYPE_ATTR_MIN_VALUE_U,
+	NL_POLICY_TYPE_ATTR_MAX_VALUE_U,
+	NL_POLICY_TYPE_ATTR_MIN_LENGTH,
+	NL_POLICY_TYPE_ATTR_MAX_LENGTH,
+	NL_POLICY_TYPE_ATTR_POLICY_IDX,
+	NL_POLICY_TYPE_ATTR_POLICY_MAXTYPE,
+	NL_POLICY_TYPE_ATTR_BITFIELD32_MASK,
+	NL_POLICY_TYPE_ATTR_PAD,
+
+	/* keep last */
+	__NL_POLICY_TYPE_ATTR_MAX,
+	NL_POLICY_TYPE_ATTR_MAX = __NL_POLICY_TYPE_ATTR_MAX - 1
+};
+
 #endif /* _UAPI__LINUX_NETLINK_H */
diff --git a/lib/nlattr.c b/lib/nlattr.c
index cace9b307781..bc5b5cf608c4 100644
--- a/lib/nlattr.c
+++ b/lib/nlattr.c
@@ -44,8 +44,22 @@ static const u8 nla_attr_minlen[NLA_TYPE_MAX+1] = {
 	[NLA_S64]	= sizeof(s64),
 };
 
+/*
+ * Nested policies might refer back to the original
+ * policy in some cases, and userspace could try to
+ * abuse that and recurse by nesting in the right
+ * ways. Limit recursion to avoid this problem.
+ */
+#define MAX_POLICY_RECURSION_DEPTH	10
+
+static int __nla_validate_parse(const struct nlattr *head, int len, int maxtype,
+				const struct nla_policy *policy,
+				unsigned int validate,
+				struct netlink_ext_ack *extack,
+				struct nlattr **tb, unsigned int depth);
+
 static int validate_nla_bitfield32(const struct nlattr *nla,
-				   const u32 *valid_flags_mask)
+				   const u32 valid_flags_mask)
 {
 	const struct nla_bitfield32 *bf = nla_data(nla);
 
@@ -53,11 +67,11 @@ static int validate_nla_bitfield32(const struct nlattr *nla,
 		return -EINVAL;
 
 	/*disallow invalid bit selector */
-	if (bf->selector & ~*valid_flags_mask)
+	if (bf->selector & ~valid_flags_mask)
 		return -EINVAL;
 
 	/*disallow invalid bit values */
-	if (bf->value & ~*valid_flags_mask)
+	if (bf->value & ~valid_flags_mask)
 		return -EINVAL;
 
 	/*disallow valid bit values that are not selected*/
@@ -70,7 +84,7 @@ static int validate_nla_bitfield32(const struct nlattr *nla,
 static int nla_validate_array(const struct nlattr *head, int len, int maxtype,
 			      const struct nla_policy *policy,
 			      struct netlink_ext_ack *extack,
-			      unsigned int validate)
+			      unsigned int validate, unsigned int depth)
 {
 	const struct nlattr *entry;
 	int rem;
@@ -87,8 +101,9 @@ static int nla_validate_array(const struct nlattr *head, int len, int maxtype,
 			return -ERANGE;
 		}
 
-		ret = __nla_validate(nla_data(entry), nla_len(entry),
-				     maxtype, policy, validate, extack);
+		ret = __nla_validate_parse(nla_data(entry), nla_len(entry),
+					   maxtype, policy, validate, extack,
+					   NULL, depth + 1);
 		if (ret < 0)
 			return ret;
 	}
@@ -96,17 +111,58 @@ static int nla_validate_array(const struct nlattr *head, int len, int maxtype,
 	return 0;
 }
 
-static int nla_validate_int_range(const struct nla_policy *pt,
-				  const struct nlattr *nla,
-				  struct netlink_ext_ack *extack)
+void nla_get_range_unsigned(const struct nla_policy *pt,
+			    struct netlink_range_validation *range)
 {
-	bool validate_min, validate_max;
-	s64 value;
+	WARN_ON_ONCE(pt->validation_type != NLA_VALIDATE_RANGE_PTR &&
+		     (pt->min < 0 || pt->max < 0));
 
-	validate_min = pt->validation_type == NLA_VALIDATE_RANGE ||
-		       pt->validation_type == NLA_VALIDATE_MIN;
-	validate_max = pt->validation_type == NLA_VALIDATE_RANGE ||
-		       pt->validation_type == NLA_VALIDATE_MAX;
+	range->min = 0;
+
+	switch (pt->type) {
+	case NLA_U8:
+		range->max = U8_MAX;
+		break;
+	case NLA_U16:
+		range->max = U16_MAX;
+		break;
+	case NLA_U32:
+		range->max = U32_MAX;
+		break;
+	case NLA_U64:
+	case NLA_MSECS:
+		range->max = U64_MAX;
+		break;
+	default:
+		WARN_ON_ONCE(1);
+		return;
+	}
+
+	switch (pt->validation_type) {
+	case NLA_VALIDATE_RANGE:
+		range->min = pt->min;
+		range->max = pt->max;
+		break;
+	case NLA_VALIDATE_RANGE_PTR:
+		*range = *pt->range;
+		break;
+	case NLA_VALIDATE_MIN:
+		range->min = pt->min;
+		break;
+	case NLA_VALIDATE_MAX:
+		range->max = pt->max;
+		break;
+	default:
+		break;
+	}
+}
+
+static int nla_validate_int_range_unsigned(const struct nla_policy *pt,
+					   const struct nlattr *nla,
+					   struct netlink_ext_ack *extack)
+{
+	struct netlink_range_validation range;
+	u64 value;
 
 	switch (pt->type) {
 	case NLA_U8:
@@ -118,6 +174,77 @@ static int nla_validate_int_range(const struct nla_policy *pt,
 	case NLA_U32:
 		value = nla_get_u32(nla);
 		break;
+	case NLA_U64:
+	case NLA_MSECS:
+		value = nla_get_u64(nla);
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	nla_get_range_unsigned(pt, &range);
+
+	if (value < range.min || value > range.max) {
+		NL_SET_ERR_MSG_ATTR(extack, nla,
+				    "integer out of range");
+		return -ERANGE;
+	}
+
+	return 0;
+}
+
+void nla_get_range_signed(const struct nla_policy *pt,
+			  struct netlink_range_validation_signed *range)
+{
+	switch (pt->type) {
+	case NLA_S8:
+		range->min = S8_MIN;
+		range->max = S8_MAX;
+		break;
+	case NLA_S16:
+		range->min = S16_MIN;
+		range->max = S16_MAX;
+		break;
+	case NLA_S32:
+		range->min = S32_MIN;
+		range->max = S32_MAX;
+		break;
+	case NLA_S64:
+		range->min = S64_MIN;
+		range->max = S64_MAX;
+		break;
+	default:
+		WARN_ON_ONCE(1);
+		return;
+	}
+
+	switch (pt->validation_type) {
+	case NLA_VALIDATE_RANGE:
+		range->min = pt->min;
+		range->max = pt->max;
+		break;
+	case NLA_VALIDATE_RANGE_PTR:
+		*range = *pt->range_signed;
+		break;
+	case NLA_VALIDATE_MIN:
+		range->min = pt->min;
+		break;
+	case NLA_VALIDATE_MAX:
+		range->max = pt->max;
+		break;
+	default:
+		break;
+	}
+}
+
+static int nla_validate_int_range_signed(const struct nla_policy *pt,
+					 const struct nlattr *nla,
+					 struct netlink_ext_ack *extack)
+{
+	struct netlink_range_validation_signed range;
+	s64 value;
+
+	switch (pt->type) {
 	case NLA_S8:
 		value = nla_get_s8(nla);
 		break;
@@ -130,22 +257,13 @@ static int nla_validate_int_range(const struct nla_policy *pt,
 	case NLA_S64:
 		value = nla_get_s64(nla);
 		break;
-	case NLA_U64:
-		/* treat this one specially, since it may not fit into s64 */
-		if ((validate_min && nla_get_u64(nla) < pt->min) ||
-		    (validate_max && nla_get_u64(nla) > pt->max)) {
-			NL_SET_ERR_MSG_ATTR(extack, nla,
-					    "integer out of range");
-			return -ERANGE;
-		}
-		return 0;
 	default:
-		WARN_ON(1);
 		return -EINVAL;
 	}
 
-	if ((validate_min && value < pt->min) ||
-	    (validate_max && value > pt->max)) {
+	nla_get_range_signed(pt, &range);
+
+	if (value < range.min || value > range.max) {
 		NL_SET_ERR_MSG_ATTR(extack, nla,
 				    "integer out of range");
 		return -ERANGE;
@@ -154,9 +272,31 @@ static int nla_validate_int_range(const struct nla_policy *pt,
 	return 0;
 }
 
+static int nla_validate_int_range(const struct nla_policy *pt,
+				  const struct nlattr *nla,
+				  struct netlink_ext_ack *extack)
+{
+	switch (pt->type) {
+	case NLA_U8:
+	case NLA_U16:
+	case NLA_U32:
+	case NLA_U64:
+	case NLA_MSECS:
+		return nla_validate_int_range_unsigned(pt, nla, extack);
+	case NLA_S8:
+	case NLA_S16:
+	case NLA_S32:
+	case NLA_S64:
+		return nla_validate_int_range_signed(pt, nla, extack);
+	default:
+		WARN_ON(1);
+		return -EINVAL;
+	}
+}
+
 static int validate_nla(const struct nlattr *nla, int maxtype,
 			const struct nla_policy *policy, unsigned int validate,
-			struct netlink_ext_ack *extack)
+			struct netlink_ext_ack *extack, unsigned int depth)
 {
 	u16 strict_start_type = policy[0].strict_start_type;
 	const struct nla_policy *pt;
@@ -174,7 +314,9 @@ static int validate_nla(const struct nlattr *nla, int maxtype,
 	BUG_ON(pt->type > NLA_TYPE_MAX);
 
 	if ((nla_attr_len[pt->type] && attrlen != nla_attr_len[pt->type]) ||
-	    (pt->type == NLA_EXACT_LEN_WARN && attrlen != pt->len)) {
+	    (pt->type == NLA_EXACT_LEN &&
+	     pt->validation_type == NLA_VALIDATE_WARN_TOO_LONG &&
+	     attrlen != pt->len)) {
 		pr_warn_ratelimited("netlink: '%s': attribute type %d has an invalid length.\n",
 				    current->comm, type);
 		if (validate & NL_VALIDATE_STRICT_ATTRS) {
@@ -200,15 +342,10 @@ static int validate_nla(const struct nlattr *nla, int maxtype,
 	}
 
 	switch (pt->type) {
-	case NLA_EXACT_LEN:
-		if (attrlen != pt->len)
-			goto out_err;
-		break;
-
 	case NLA_REJECT:
-		if (extack && pt->validation_data) {
+		if (extack && pt->reject_message) {
 			NL_SET_BAD_ATTR(extack, nla);
-			extack->_msg = pt->validation_data;
+			extack->_msg = pt->reject_message;
 			return -EINVAL;
 		}
 		err = -EINVAL;
@@ -223,7 +360,7 @@ static int validate_nla(const struct nlattr *nla, int maxtype,
 		if (attrlen != sizeof(struct nla_bitfield32))
 			goto out_err;
 
-		err = validate_nla_bitfield32(nla, pt->validation_data);
+		err = validate_nla_bitfield32(nla, pt->bitfield32_valid);
 		if (err)
 			goto out_err;
 		break;
@@ -268,10 +405,11 @@ static int validate_nla(const struct nlattr *nla, int maxtype,
 			break;
 		if (attrlen < NLA_HDRLEN)
 			goto out_err;
-		if (pt->validation_data) {
-			err = __nla_validate(nla_data(nla), nla_len(nla), pt->len,
-					     pt->validation_data, validate,
-					     extack);
+		if (pt->nested_policy) {
+			err = __nla_validate_parse(nla_data(nla), nla_len(nla),
+						   pt->len, pt->nested_policy,
+						   validate, extack, NULL,
+						   depth + 1);
 			if (err < 0) {
 				/*
 				 * return directly to preserve the inner
@@ -289,12 +427,12 @@ static int validate_nla(const struct nlattr *nla, int maxtype,
 			break;
 		if (attrlen < NLA_HDRLEN)
 			goto out_err;
-		if (pt->validation_data) {
+		if (pt->nested_policy) {
 			int err;
 
 			err = nla_validate_array(nla_data(nla), nla_len(nla),
-						 pt->len, pt->validation_data,
-						 extack, validate);
+						 pt->len, pt->nested_policy,
+						 extack, validate, depth);
 			if (err < 0) {
 				/*
 				 * return directly to preserve the inner
@@ -317,6 +455,13 @@ static int validate_nla(const struct nlattr *nla, int maxtype,
 			goto out_err;
 		break;
 
+	case NLA_EXACT_LEN:
+		if (pt->validation_type != NLA_VALIDATE_WARN_TOO_LONG) {
+			if (attrlen != pt->len)
+				goto out_err;
+			break;
+		}
+		/* fall through */
 	default:
 		if (pt->len)
 			minlen = pt->len;
@@ -332,6 +477,7 @@ static int validate_nla(const struct nlattr *nla, int maxtype,
 	case NLA_VALIDATE_NONE:
 		/* nothing to do */
 		break;
+	case NLA_VALIDATE_RANGE_PTR:
 	case NLA_VALIDATE_RANGE:
 	case NLA_VALIDATE_MIN:
 	case NLA_VALIDATE_MAX:
@@ -358,11 +504,17 @@ static int __nla_validate_parse(const struct nlattr *head, int len, int maxtype,
 				const struct nla_policy *policy,
 				unsigned int validate,
 				struct netlink_ext_ack *extack,
-				struct nlattr **tb)
+				struct nlattr **tb, unsigned int depth)
 {
 	const struct nlattr *nla;
 	int rem;
 
+	if (depth >= MAX_POLICY_RECURSION_DEPTH) {
+		NL_SET_ERR_MSG(extack,
+			       "allowed policy recursion depth exceeded");
+		return -EINVAL;
+	}
+
 	if (tb)
 		memset(tb, 0, sizeof(struct nlattr *) * (maxtype + 1));
 
@@ -379,7 +531,7 @@ static int __nla_validate_parse(const struct nlattr *head, int len, int maxtype,
 		}
 		if (policy) {
 			int err = validate_nla(nla, maxtype, policy,
-					       validate, extack);
+					       validate, extack, depth);
 
 			if (err < 0)
 				return err;
@@ -421,7 +573,7 @@ int __nla_validate(const struct nlattr *head, int len, int maxtype,
 		   struct netlink_ext_ack *extack)
 {
 	return __nla_validate_parse(head, len, maxtype, policy, validate,
-				    extack, NULL);
+				    extack, NULL, 0);
 }
 EXPORT_SYMBOL(__nla_validate);
 
@@ -476,7 +628,7 @@ int __nla_parse(struct nlattr **tb, int maxtype,
 		struct netlink_ext_ack *extack)
 {
 	return __nla_validate_parse(head, len, maxtype, policy, validate,
-				    extack, tb);
+				    extack, tb, 0);
 }
 EXPORT_SYMBOL(__nla_parse);
 
diff --git a/net/netlink/Makefile b/net/netlink/Makefile
index de42df7f0068..e05202708c90 100644
--- a/net/netlink/Makefile
+++ b/net/netlink/Makefile
@@ -3,7 +3,7 @@
 # Makefile for the netlink driver.
 #
 
-obj-y  				:= af_netlink.o genetlink.o
+obj-y  				:= af_netlink.o genetlink.o policy.o
 
 obj-$(CONFIG_NETLINK_DIAG)	+= netlink_diag.o
 netlink_diag-y			:= diag.o
diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c
index 9f357aa22b94..2f049692e012 100644
--- a/net/netlink/genetlink.c
+++ b/net/netlink/genetlink.c
@@ -1043,6 +1043,80 @@ static int genl_ctrl_event(int event, const struct genl_family *family,
 	return 0;
 }
 
+static int ctrl_dumppolicy(struct sk_buff *skb, struct netlink_callback *cb)
+{
+	const struct genl_family *rt;
+	unsigned int fam_id = cb->args[0];
+	int err;
+
+	if (!fam_id) {
+		struct nlattr *tb[CTRL_ATTR_MAX + 1];
+
+		err = genlmsg_parse(cb->nlh, &genl_ctrl, tb,
+				    genl_ctrl.maxattr,
+				    genl_ctrl.policy, cb->extack);
+		if (err)
+			return err;
+
+		if (!tb[CTRL_ATTR_FAMILY_ID] && !tb[CTRL_ATTR_FAMILY_NAME])
+			return -EINVAL;
+
+		if (tb[CTRL_ATTR_FAMILY_ID]) {
+			fam_id = nla_get_u16(tb[CTRL_ATTR_FAMILY_ID]);
+		} else {
+			rt = genl_family_find_byname(
+				nla_data(tb[CTRL_ATTR_FAMILY_NAME]));
+			if (!rt)
+				return -ENOENT;
+			fam_id = rt->id;
+		}
+	}
+
+	rt = genl_family_find_byid(fam_id);
+	if (!rt)
+		return -ENOENT;
+
+	if (!rt->policy)
+		return -ENODATA;
+
+	err = netlink_policy_dump_start(rt->policy, rt->maxattr, &cb->args[1]);
+	if (err)
+		return err;
+
+	while (netlink_policy_dump_loop(&cb->args[1])) {
+		void *hdr;
+		struct nlattr *nest;
+
+		hdr = genlmsg_put(skb, NETLINK_CB(cb->skb).portid,
+				  cb->nlh->nlmsg_seq, &genl_ctrl,
+				  NLM_F_MULTI, CTRL_CMD_GETPOLICY);
+		if (!hdr)
+			goto nla_put_failure;
+
+		if (nla_put_u16(skb, CTRL_ATTR_FAMILY_ID, rt->id))
+			goto nla_put_failure;
+
+		nest = nla_nest_start(skb, CTRL_ATTR_POLICY);
+		if (!nest)
+			goto nla_put_failure;
+
+		if (netlink_policy_dump_write(skb, cb->args[1]))
+			goto nla_put_failure;
+
+		nla_nest_end(skb, nest);
+
+		genlmsg_end(skb, hdr);
+		continue;
+
+nla_put_failure:
+		genlmsg_cancel(skb, hdr);
+		break;
+	}
+
+	cb->args[0] = fam_id;
+	return skb->len;
+}
+
 static const struct genl_ops genl_ctrl_ops[] = {
 	{
 		.cmd		= CTRL_CMD_GETFAMILY,
@@ -1050,6 +1124,10 @@ static const struct genl_ops genl_ctrl_ops[] = {
 		.doit		= ctrl_getfamily,
 		.dumpit		= ctrl_dumpfamily,
 	},
+	{
+		.cmd		= CTRL_CMD_GETPOLICY,
+		.dumpit		= ctrl_dumppolicy,
+	},
 };
 
 static const struct genl_multicast_group genl_ctrl_groups[] = {
diff --git a/net/netlink/policy.c b/net/netlink/policy.c
new file mode 100644
index 000000000000..f6491853c797
--- /dev/null
+++ b/net/netlink/policy.c
@@ -0,0 +1,308 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * NETLINK      Policy advertisement to userspace
+ *
+ * 		Authors:	Johannes Berg <johannes@sipsolutions.net>
+ *
+ * Copyright 2019 Intel Corporation
+ */
+
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/types.h>
+#include <net/netlink.h>
+
+#define INITIAL_POLICIES_ALLOC	10
+
+struct nl_policy_dump {
+	unsigned int policy_idx;
+	unsigned int attr_idx;
+	unsigned int n_alloc;
+	struct {
+		const struct nla_policy *policy;
+		unsigned int maxtype;
+	} policies[];
+};
+
+static int add_policy(struct nl_policy_dump **statep,
+		      const struct nla_policy *policy,
+		      unsigned int maxtype)
+{
+	struct nl_policy_dump *state = *statep;
+	unsigned int n_alloc, i;
+
+	if (!policy || !maxtype)
+		return 0;
+
+	for (i = 0; i < state->n_alloc; i++) {
+		if (state->policies[i].policy == policy)
+			return 0;
+
+		if (!state->policies[i].policy) {
+			state->policies[i].policy = policy;
+			state->policies[i].maxtype = maxtype;
+			return 0;
+		}
+	}
+
+	n_alloc = state->n_alloc + INITIAL_POLICIES_ALLOC;
+	state = krealloc(state, struct_size(state, policies, n_alloc),
+			 GFP_KERNEL);
+	if (!state)
+		return -ENOMEM;
+
+	state->policies[state->n_alloc].policy = policy;
+	state->policies[state->n_alloc].maxtype = maxtype;
+	state->n_alloc = n_alloc;
+	*statep = state;
+
+	return 0;
+}
+
+static unsigned int get_policy_idx(struct nl_policy_dump *state,
+				   const struct nla_policy *policy)
+{
+	unsigned int i;
+
+	for (i = 0; i < state->n_alloc; i++) {
+		if (state->policies[i].policy == policy)
+			return i;
+	}
+
+	WARN_ON_ONCE(1);
+	return -1;
+}
+
+int netlink_policy_dump_start(const struct nla_policy *policy,
+			      unsigned int maxtype,
+                              unsigned long *_state)
+{
+	struct nl_policy_dump *state;
+	unsigned int policy_idx;
+	int err;
+
+	/* also returns 0 if "*_state" is our ERR_PTR() end marker */
+	if (*_state)
+		return 0;
+
+	/*
+	 * walk the policies and nested ones first, and build
+	 * a linear list of them.
+	 */
+