linux-kernel - [PATCH 4.19 16/88] batman-adv: Avoid uninitialized chaddr when handling DHCP

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Tue,  8 Sep 2020 17:25:17 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        syzbot+ab16e463b903f5a37036@...kaller.appspotmail.com,
        Sven Eckelmann <sven@...fation.org>,
        Antonio Quartulli <a@...table.cc>,
        Simon Wunderlich <sw@...onwunderlich.de>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.19 16/88] batman-adv: Avoid uninitialized chaddr when handling DHCP

From: Sven Eckelmann <sven@...fation.org>

[ Upstream commit 303216e76dcab6049c9d42390b1032f0649a8206 ]

The gateway client code can try to optimize the delivery of DHCP packets to
avoid broadcasting them through the whole mesh. But also transmissions to
the client can be optimized by looking up the destination via the chaddr of
the DHCP packet.

But the chaddr is currently only done when chaddr is fully inside the
non-paged area of the skbuff. Otherwise it will not be initialized and the
unoptimized path should have been taken.

But the implementation didn't handle this correctly. It didn't retrieve the
correct chaddr but still tried to perform the TT lookup with this
uninitialized memory.

Reported-by: syzbot+ab16e463b903f5a37036@...kaller.appspotmail.com
Fixes: 6c413b1c22a2 ("batman-adv: send every DHCP packet as bat-unicast")
Signed-off-by: Sven Eckelmann <sven@...fation.org>
Acked-by: Antonio Quartulli <a@...table.cc>
Signed-off-by: Simon Wunderlich <sw@...onwunderlich.de>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 net/batman-adv/gateway_client.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/batman-adv/gateway_client.c b/net/batman-adv/gateway_client.c
index 140c61a3f1ecf..0c59fefc13719 100644
--- a/net/batman-adv/gateway_client.c
+++ b/net/batman-adv/gateway_client.c
@@ -714,8 +714,10 @@ batadv_gw_dhcp_recipient_get(struct sk_buff *skb, unsigned int *header_len,
 
 	chaddr_offset = *header_len + BATADV_DHCP_CHADDR_OFFSET;
 	/* store the client address if the message is going to a client */
-	if (ret == BATADV_DHCP_TO_CLIENT &&
-	    pskb_may_pull(skb, chaddr_offset + ETH_ALEN)) {
+	if (ret == BATADV_DHCP_TO_CLIENT) {
+		if (!pskb_may_pull(skb, chaddr_offset + ETH_ALEN))
+			return BATADV_DHCP_NO;
+
 		/* check if the DHCP packet carries an Ethernet DHCP */
 		p = skb->data + *header_len + BATADV_DHCP_HTYPE_OFFSET;
 		if (*p != BATADV_DHCP_HTYPE_ETHERNET)
-- 
2.25.1