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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        syzbot+de00a87b8644a582ae79@syzkaller.appspotmail.com,
        Xin Long <lucien.xin@gmail.com>,
        "David S. Miller" <davem@davemloft.net>
Subject: [PATCH 4.9 28/41] tipc: check link name with right length in tipc_nl_compat_link_set
Date:   Tue, 30 Apr 2019 13:38:39 +0200
Message-Id: <20190430113531.365800624@linuxfoundation.org>
In-Reply-To: <20190430113524.451237916@linuxfoundation.org>
References: <20190430113524.451237916@linuxfoundation.org>
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From: Xin Long <lucien.xin@gmail.com>

commit 8c63bf9ab4be8b83bd8c34aacfd2f1d2c8901c8a upstream.

A similar issue as fixed by Patch "tipc: check bearer name with right
length in tipc_nl_compat_bearer_enable" was also found by syzbot in
tipc_nl_compat_link_set().

The length to check with should be 'TLV_GET_DATA_LEN(msg->req) -
offsetof(struct tipc_link_config, name)'.

Reported-by: syzbot+de00a87b8644a582ae79@syzkaller.appspotmail.com
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 net/tipc/netlink_compat.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

--- a/net/tipc/netlink_compat.c
+++ b/net/tipc/netlink_compat.c
@@ -768,7 +768,12 @@ static int tipc_nl_compat_link_set(struc
 
 	lc = (struct tipc_link_config *)TLV_DATA(msg->req);
 
-	len = min_t(int, TLV_GET_DATA_LEN(msg->req), TIPC_MAX_LINK_NAME);
+	len = TLV_GET_DATA_LEN(msg->req);
+	len -= offsetof(struct tipc_link_config, name);
+	if (len <= 0)
+		return -EINVAL;
+
+	len = min_t(int, len, TIPC_MAX_LINK_NAME);
 	if (!string_is_valid(lc->name, len))
 		return -EINVAL;