linux-kernel - [PATCH] netlink: policy: correct validation type check

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Message-Id: <20200831202805.8ca5a2fe1ffb.I46f0d5bee0a774517aeec539620895a473dd2299@changeid>
Date:   Mon, 31 Aug 2020 20:28:05 +0200
From:   Johannes Berg <johannes@...solutions.net>
To:     netdev@...r.kernel.org
Cc:     kuba@...nel.org, linux-kernel@...r.kernel.org, davem@...emloft.net,
        syzkaller-bugs@...glegroups.com,
        Johannes Berg <johannes.berg@...el.com>,
        syzbot+353df1490da781637624@...kaller.appspotmail.com
Subject: [PATCH] netlink: policy: correct validation type check

From: Johannes Berg <johannes.berg@...el.com>

In the policy export for binary attributes I erroneously used
a != NLA_VALIDATE_NONE comparison instead of checking for the
two possible values, which meant that if a validation function
pointer ended up aliasing the min/max as negatives, we'd hit
a warning in nla_get_range_unsigned().

Fix this to correctly check for only the two types that should
be handled here, i.e. range with or without warn-too-long.

Reported-by: syzbot+353df1490da781637624@...kaller.appspotmail.com
Fixes: 8aa26c575fb3 ("netlink: make NLA_BINARY validation more flexible")
Signed-off-by: Johannes Berg <johannes.berg@...el.com>
---
 net/netlink/policy.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/netlink/policy.c b/net/netlink/policy.c
index 7b1f50531cd3..5c9e7530865f 100644
--- a/net/netlink/policy.c
+++ b/net/netlink/policy.c
@@ -264,7 +264,8 @@ int netlink_policy_dump_write(struct sk_buff *skb, unsigned long _state)
 		else
 			type = NL_ATTR_TYPE_BINARY;
 
-		if (pt->validation_type != NLA_VALIDATE_NONE) {
+		if (pt->validation_type == NLA_VALIDATE_RANGE ||
+		    pt->validation_type == NLA_VALIDATE_RANGE_WARN_TOO_LONG) {
 			struct netlink_range_validation range;
 
 			nla_get_range_unsigned(pt, &range);
-- 
2.26.2