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Wed, 12 Feb 2025 03:34:13 -0800 (PST) From: Oscar Maes To: netdev@vger.kernel.org Cc: davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, viro@zeniv.linux.org.uk, jiri@resnulli.us, linux-kernel@vger.kernel.org, security@kernel.org, Oscar Maes , syzbot Subject: [PATCH net] net: 802: enforce underlying device type for GARP and MRP Date: Wed, 12 Feb 2025 12:32:18 +0100 Message-Id: <20250212113218.9859-1-oscmaes92@gmail.com> X-Mailer: git-send-email 2.39.5 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: kuba@kernel.org When creating a VLAN device, we initialize GARP (garp_init_applicant) and MRP (mrp_init_applicant) for the underlying device. As part of the initialization process, we add the multicast address of each applicant to the underlying device, by calling dev_mc_add. __dev_mc_add uses dev->addr_len to determine the length of the new multicast address. This causes an out-of-bounds read if dev->addr_len is greater than 6, since the multicast addresses provided by GARP and MRP are only 6 bytes long. This behaviour can be reproduced using the following commands: ip tunnel add gretest mode ip6gre local ::1 remote ::2 dev lo ip l set up dev gretest ip link add link gretest name vlantest type vlan id 100 Then, the following command will display the address of garp_pdu_rcv: ip maddr show | grep 01:80:c2:00:00:21 Fix this by enforcing the type and address length of the underlying device during GARP and MRP initialization. Fixes: 22bedad3ce11 ("net: convert multicast list to list_head") Reported-by: syzbot Closes: https://lore.kernel.org/netdev/000000000000ca9a81061a01ec20@google.com/ Signed-off-by: Oscar Maes --- net/802/garp.c | 5 +++++ net/802/mrp.c | 5 +++++ 2 files changed, 10 insertions(+) diff --git a/net/802/garp.c b/net/802/garp.c index 27f0ab146..2f383ee73 100644 --- a/net/802/garp.c +++ b/net/802/garp.c @@ -9,6 +9,7 @@ #include #include #include +#include #include #include #include @@ -574,6 +575,10 @@ int garp_init_applicant(struct net_device *dev, struct garp_application *appl) ASSERT_RTNL(); + err = -EINVAL; + if (dev->type != ARPHRD_ETHER || dev->addr_len != ETH_ALEN) + goto err1; + if (!rtnl_dereference(dev->garp_port)) { err = garp_init_port(dev); if (err < 0) diff --git a/net/802/mrp.c b/net/802/mrp.c index e0c96d0da..1efee0b39 100644 --- a/net/802/mrp.c +++ b/net/802/mrp.c @@ -12,6 +12,7 @@ #include #include #include +#include #include #include #include @@ -859,6 +860,10 @@ int mrp_init_applicant(struct net_device *dev, struct mrp_application *appl) ASSERT_RTNL(); + err = -EINVAL; + if (dev->type != ARPHRD_ETHER || dev->addr_len != ETH_ALEN) + goto err1; + if (!rtnl_dereference(dev->mrp_port)) { err = mrp_init_port(dev); if (err < 0)