Re: [syzbot] Re: [syzbot] [net?] KASAN: slab-use-after-free Read in __ethtool_get_link_ksettings

[syzbot <syzbot+5fe14f2ff4ccbace9a26@syzkaller.appspotmail.com>]

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***

Subject: Re: [syzbot] [net?] KASAN: slab-use-after-free Read in __ethtool_get_link_ksettings
Author: leon@kernel.org

On Mon, Oct 07, 2024 at 06:44:02PM -0700, syzbot wrote:
> syzbot has bisected this issue to:
> 
> commit 5f8ca04fdd3c66a322ea318b5f1cb684dd56e5b2
> Author: Chiara Meiohas <cmeiohas@nvidia.com>
> Date:   Mon Sep 9 17:30:22 2024 +0000
> 
>     RDMA/device: Remove optimization in ib_device_get_netdev()
> 
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=16db2327980000
> start commit:   c4a14f6d9d17 ipv4: ip_gre: Fix drops of small packets in i..
> git tree:       net
> final oops:     https://syzkaller.appspot.com/x/report.txt?x=15db2327980000
> console output: https://syzkaller.appspot.com/x/log.txt?x=11db2327980000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=b2d4fdf18a83ec0b
> dashboard link: https://syzkaller.appspot.com/bug?extid=5fe14f2ff4ccbace9a26
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11eca3d0580000
> 
> Reported-by: syzbot+5fe14f2ff4ccbace9a26@syzkaller.appspotmail.com
> Fixes: 5f8ca04fdd3c ("RDMA/device: Remove optimization in ib_device_get_netdev()")
> 
> For information about bisection process see: https://goo.gl/tpsmEJ#bisection

#syz test: https://git.kernel.org/pub/scm/linux/kernel/git/rdma/rdma.git for-next

diff --git a/drivers/infiniband/core/device.c b/drivers/infiniband/core/device.c
index e029401b5680..0b7e5245ffbc 100644
--- a/drivers/infiniband/core/device.c
+++ b/drivers/infiniband/core/device.c
@@ -2061,19 +2061,14 @@ void ib_dispatch_event_clients(struct ib_event *event)
 	up_read(&event->device->event_handler_rwsem);
 }
 
-static int iw_query_port(struct ib_device *device,
-			   u32 port_num,
-			   struct ib_port_attr *port_attr)
+static int iw_query_port(struct ib_device *device, u32 port_num,
+			 struct ib_port_attr *port_attr,
+			 struct net_device *netdev)
 {
 	struct in_device *inetdev;
-	struct net_device *netdev;
 
 	memset(port_attr, 0, sizeof(*port_attr));
 
-	netdev = ib_device_get_netdev(device, port_num);
-	if (!netdev)
-		return -ENODEV;
-
 	port_attr->max_mtu = IB_MTU_4096;
 	port_attr->active_mtu = ib_mtu_int_to_enum(netdev->mtu);
 
@@ -2096,7 +2091,6 @@ static int iw_query_port(struct ib_device *device,
 		rcu_read_unlock();
 	}
 
-	dev_put(netdev);
 	return device->ops.query_port(device, port_num, port_attr);
 }
 
@@ -2134,13 +2128,27 @@ int ib_query_port(struct ib_device *device,
 		  u32 port_num,
 		  struct ib_port_attr *port_attr)
 {
+	struct net_device *netdev = NULL;
+	int ret;
+
 	if (!rdma_is_port_valid(device, port_num))
 		return -EINVAL;
 
+	if (rdma_protocol_iwarp(device, port_num) ||
+	    rdma_protocol_roce(device, port_num)) {
+		netdev = ib_device_get_netdev(device, port_num);
+		if (!netdev)
+			return -ENODEV;
+	}
+
 	if (rdma_protocol_iwarp(device, port_num))
-		return iw_query_port(device, port_num, port_attr);
+		ret = iw_query_port(device, port_num, port_attr, netdev);
 	else
-		return __ib_query_port(device, port_num, port_attr);
+		ret = __ib_query_port(device, port_num, port_attr);
+	if (netdev)
+		dev_put(netdev);
+	return ret;
+
 }
 EXPORT_SYMBOL(ib_query_port);