netlink: fix policy dump for int with validation callback

JIRA: https://issues.redhat.com/browse/RHEL-104975

commit a968760
Author: Jakub Kicinski <kuba@kernel.org>
Date:   Fri May 9 14:27:51 2025 -0700

    netlink: fix policy dump for int with validation callback

    Recent devlink change added validation of an integer value
    via NLA_POLICY_VALIDATE_FN, for sparse enums. Handle this
    in policy dump. We can't extract any info out of the callback,
    so report only the type.

    Fixes: 429ac62 ("devlink: define enum for attr types of dynamic attributes")
    Reported-by: syzbot+01eb26848144516e7f0a@syzkaller.appspotmail.com
    Link: https://patch.msgid.link/20250509212751.1905149-1-kuba@kernel.org
    Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Signed-off-by: Ivan Vecera <ivecera@redhat.com>

Author: ivecera

include/net/netlink.h

@@ -318,7 +318,13 @@ enum nla_policy_validation {
  *    All other            Unused - but note that it's a union
  *
  * Meaning of `validate' field, use via NLA_POLICY_VALIDATE_FN:
+ *    NLA_U8, NLA_U16,
+ *    NLA_U32, NLA_U64,
+ *    NLA_S8, NLA_S16,
+ *    NLA_S32, NLA_S64,
+ *    NLA_MSECS,
  *    NLA_BINARY           Validation function called for the attribute.
+ *
  *    All other            Unused - but note that it's a union
  *
  * Example:

net/netlink/policy.c

@@ -311,6 +311,8 @@ __netlink_policy_dump_write_attr(struct netlink_policy_dump_state *state,
 					      NL_POLICY_TYPE_ATTR_PAD))
 				goto nla_put_failure;
 			break;
+		} else if (pt->validation_type == NLA_VALIDATE_FUNCTION) {
+			break;
 		}
 
 		nla_get_range_unsigned(pt, &range);
@@ -340,6 +342,9 @@ __netlink_policy_dump_write_attr(struct netlink_policy_dump_state *state,
 		else
 			type = NL_ATTR_TYPE_SINT;
 
+		if (pt->validation_type == NLA_VALIDATE_FUNCTION)
+			break;
+
 		nla_get_range_signed(pt, &range);
 
 		if (nla_put_s64(skb, NL_POLICY_TYPE_ATTR_MIN_VALUE_S,