[SRU][F:linux-bluefield][PATCH 1/4] netlink: add mask validation

[Bodong Wang]

From: Jakub Kicinski <kuba at kernel.org>

BugLink: https://bugs.launchpad.net/bugs/1944390

We don't have good validation policy for existing unsigned int attrs
which serve as flags (for new ones we could use NLA_BITFIELD32).
With increased use of policy dumping having the validation be
expressed as part of the policy is important. Add validation
policy in form of a mask of supported/valid bits.

Support u64 in the uAPI to be future-proof, but really for now
the embedded mask member can only hold 32 bits, so anything with
bit 32+ set will always fail validation.

Signed-off-by: Jakub Kicinski <kuba at kernel.org>
Signed-off-by: David S. Miller <davem at davemloft.net>
(Backported from upstream commit bdbb4e29df8b790db50cb73ce25d23543329f05f)
Signed-off-by: Paul Blakey <paulb at nvidia.com>
[Paul: Changes for patch to apply:
       added missing RANGE_PTR to enum nla_policy_validation
       added missing helpers __NLA_IS_.*INT_TYPE()
       removed unneeded uapi netlink changes as enum netlink_policy_type_attr
       doesn't exist]
Signed-off-by: Bodong Wang <bodong at nvidia.com>
---
 include/net/netlink.h | 16 ++++++++++++++++
 lib/nlattr.c          | 36 ++++++++++++++++++++++++++++++++++++
 2 files changed, 52 insertions(+)

diff --git a/include/net/netlink.h b/include/net/netlink.h
index b140c8f..22dd99b 100644
--- a/include/net/netlink.h
+++ b/include/net/netlink.h
@@ -194,6 +194,8 @@ enum nla_policy_validation {
 	NLA_VALIDATE_RANGE,
 	NLA_VALIDATE_MIN,
 	NLA_VALIDATE_MAX,
+	NLA_VALIDATE_MASK,
+	NLA_VALIDATE_RANGE_PTR,
 	NLA_VALIDATE_FUNCTION,
 };
 
@@ -294,6 +296,7 @@ struct nla_policy {
 	u16		len;
 	union {
 		const void *validation_data;
+		const u32 mask;
 		struct {
 			s16 min, max;
 		};
@@ -337,12 +340,19 @@ struct nla_policy {
 #define NLA_POLICY_NESTED_ARRAY(policy) \
 	_NLA_POLICY_NESTED_ARRAY(ARRAY_SIZE(policy) - 1, policy)
 
+#define __NLA_IS_UINT_TYPE(tp)						\
+	(tp == NLA_U8 || tp == NLA_U16 || tp == NLA_U32 || tp == NLA_U64)
+#define __NLA_IS_SINT_TYPE(tp)						\
+	(tp == NLA_S8 || tp == NLA_S16 || tp == NLA_S32 || tp == NLA_S64)
+
 #define __NLA_ENSURE(condition) BUILD_BUG_ON_ZERO(!(condition))
 #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)
+#define NLA_ENSURE_UINT_TYPE(tp)			\
+	(__NLA_ENSURE(__NLA_IS_UINT_TYPE(tp)) + tp)
 #define NLA_ENSURE_NO_VALIDATION_PTR(tp)		\
 	(__NLA_ENSURE(tp != NLA_BITFIELD32 &&		\
 		      tp != NLA_REJECT &&		\
@@ -368,6 +378,12 @@ struct nla_policy {
 	.max = _max,					\
 }
 
+#define NLA_POLICY_MASK(tp, _mask) {			\
+	.type = NLA_ENSURE_UINT_TYPE(tp),		\
+	.validation_type = NLA_VALIDATE_MASK,		\
+	.mask = _mask,					\
+}
+
 #define NLA_POLICY_VALIDATE_FN(tp, fn, ...) {		\
 	.type = NLA_ENSURE_NO_VALIDATION_PTR(tp),	\
 	.validation_type = NLA_VALIDATE_FUNCTION,	\
diff --git a/lib/nlattr.c b/lib/nlattr.c
index 0d84f79..c94b014 100644
--- a/lib/nlattr.c
+++ b/lib/nlattr.c
@@ -154,6 +154,37 @@ static int nla_validate_int_range(const struct nla_policy *pt,
 	return 0;
 }
 
+static int nla_validate_mask(const struct nla_policy *pt,
+			     const struct nlattr *nla,
+			     struct netlink_ext_ack *extack)
+{
+	u64 value;
+
+	switch (pt->type) {
+	case NLA_U8:
+		value = nla_get_u8(nla);
+		break;
+	case NLA_U16:
+		value = nla_get_u16(nla);
+		break;
+	case NLA_U32:
+		value = nla_get_u32(nla);
+		break;
+	case NLA_U64:
+		value = nla_get_u64(nla);
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	if (value & ~(u64)pt->mask) {
+		NL_SET_ERR_MSG_ATTR(extack, nla, "reserved bit set");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
 static int validate_nla(const struct nlattr *nla, int maxtype,
 			const struct nla_policy *policy, unsigned int validate,
 			struct netlink_ext_ack *extack)
@@ -339,6 +370,11 @@ static int validate_nla(const struct nlattr *nla, int maxtype,
 		if (err)
 			return err;
 		break;
+	case NLA_VALIDATE_MASK:
+		err = nla_validate_mask(pt, nla, extack);
+		if (err)
+			return err;
+		break;
 	case NLA_VALIDATE_FUNCTION:
 		if (pt->validate) {
 			err = pt->validate(nla, extack);
-- 
1.8.3.1