netdev - [PATCH net-next] netlink: fix policy dump for int with validation callback

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Message-ID: <20250509212751.1905149-1-kuba@kernel.org>
Date: Fri,  9 May 2025 14:27:51 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: davem@...emloft.net
Cc: netdev@...r.kernel.org,
	edumazet@...gle.com,
	pabeni@...hat.com,
	andrew+netdev@...n.ch,
	horms@...nel.org,
	Jakub Kicinski <kuba@...nel.org>,
	syzbot+01eb26848144516e7f0a@...kaller.appspotmail.com,
	jiri@...nulli.us,
	saeedm@...dia.com
Subject: [PATCH net-next] 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: 429ac6211494 ("devlink: define enum for attr types of dynamic attributes")
Reported-by: syzbot+01eb26848144516e7f0a@...kaller.appspotmail.com
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
---
CC: jiri@...nulli.us
CC: saeedm@...dia.com
---
 include/net/netlink.h | 6 ++++++
 net/netlink/policy.c  | 5 +++++
 2 files changed, 11 insertions(+)

diff --git a/include/net/netlink.h b/include/net/netlink.h
index 82e07e272290..90a560dc167a 100644
--- a/include/net/netlink.h
+++ b/include/net/netlink.h
@@ -321,7 +321,13 @@ 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:
diff --git a/net/netlink/policy.c b/net/netlink/policy.c
index 1f8909c16f14..99458da6be32 100644
--- a/net/netlink/policy.c
+++ b/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,
-- 
2.49.0