[PATCH net v3 0/2] team: fix header_ops type confusion and add selftest

[PATCH net v3 0/2] team: fix header_ops type confusion and add selftest

[Jiayuan Chen]

Hi,

This patch series fixes a panic reported by syzkaller in the team/bond/gre
stacked non-Ethernet configuration:
https://syzkaller.appspot.com/bug?extid=3d8bc31c45e11450f24c

The first patch fixes the header_ops type confusion / parse recursion
context issue in team. The second patch adds a selftest to reproduce the
reported scenario and prevent regressions in the future.

Thanks.

---
Changes in v3:
- Clarify syzbot crash path in commit message
- Fix shellcheck warnings in selftest
- Fix config entry sorting order
- Update comment per AI review feedback

Changes in v2:
- The same fix approach was applied to bonding first, but could cause
  infinite recursion in bond_header_parse(). Eric spotted the issue and
  fixed it in:
  b7405dcf7385 ("bonding: prevent potential infinite loop in bond_header_parse()")
  After that fix landed, we continue with the same approach to fix team.

v1: https://lore.kernel.org/netdev/20260314062306.212765-1-jiayuan.chen@linux.dev/
v2: https://lore.kernel.org/netdev/20260317124606.157035-1-jiayuan.chen@linux.dev/

Jiayuan Chen (2):
  team: fix header_ops type confusion with non-Ethernet ports
  selftests: team: add non-Ethernet header_ops reproducer

 drivers/net/team/team_core.c                  | 65 ++++++++++++++++++-
 .../selftests/drivers/net/team/Makefile       |  1 +
 .../testing/selftests/drivers/net/team/config |  2 +
 .../drivers/net/team/non_ether_header_ops.sh  | 41 ++++++++++++
 4 files changed, 108 insertions(+), 1 deletion(-)
 create mode 100755 tools/testing/selftests/drivers/net/team/non_ether_header_ops.sh

-- 
2.43.0

[PATCH net v3 1/2] team: fix header_ops type confusion with non-Ethernet ports

[Jiayuan Chen]

From: Jiayuan Chen <jiayuan.chen@shopee.com>

Similar to commit 950803f72547 ("bonding: fix type confusion in
bond_setup_by_slave()") team has the same class of header_ops type
confusion.

For non-Ethernet ports, team_setup_by_port() copies port_dev->header_ops
directly. When the team device later calls dev_hard_header() or
dev_parse_header(), these callbacks can run with the team net_device
instead of the real lower device, so netdev_priv(dev) is interpreted as
the wrong private type and can crash.

The syzbot report shows a crash in bond_header_create(), but the root
cause is in team: the topology is gre -> bond -> team, and team calls
the inherited header_ops with its own net_device instead of the lower
device, so bond_header_create() receives a team device and interprets
netdev_priv() as bonding private data, causing a type confusion crash.

Fix this by introducing team header_ops wrappers for create/parse,
selecting a team port under RCU, and calling the lower device callbacks
with port->dev, so each callback always sees the correct net_device
context.

Also pass the selected lower device to the lower parse callback, so
recursion is bounded in stacked non-Ethernet topologies and parse
callbacks always run with the correct device context.

Fixes: 1d76efe1577b ("team: add support for non-ethernet devices")
Reported-by: syzbot+3d8bc31c45e11450f24c@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/69b46af7.050a0220.36eb34.000e.GAE@google.com/T/
Cc: Jiayuan Chen <jiayuan.chen@linux.dev>
Signed-off-by: Jiayuan Chen <jiayuan.chen@shopee.com>
---
 drivers/net/team/team_core.c | 65 +++++++++++++++++++++++++++++++++++-
 1 file changed, 64 insertions(+), 1 deletion(-)

diff --git a/drivers/net/team/team_core.c b/drivers/net/team/team_core.c
index b7282f5c9632..120aeb539d9f 100644
--- a/drivers/net/team/team_core.c
+++ b/drivers/net/team/team_core.c
@@ -2058,6 +2058,68 @@ static const struct ethtool_ops team_ethtool_ops = {
  * rt netlink interface
  ***********************/
 
+/* For tx path we need a linkup && enabled port and for parse any port
+ * suffices.
+ */
+static struct team_port *team_header_port_get_rcu(struct team *team,
+						  bool txable)
+{
+	struct team_port *port;
+
+	list_for_each_entry_rcu(port, &team->port_list, list) {
+		if (!txable || team_port_txable(port))
+			return port;
+	}
+
+	return NULL;
+}
+
+static int team_header_create(struct sk_buff *skb, struct net_device *team_dev,
+			      unsigned short type, const void *daddr,
+			      const void *saddr, unsigned int len)
+{
+	struct team *team = netdev_priv(team_dev);
+	const struct header_ops *port_ops;
+	struct team_port *port;
+	int ret = 0;
+
+	rcu_read_lock();
+	port = team_header_port_get_rcu(team, true);
+	if (port) {
+		port_ops = READ_ONCE(port->dev->header_ops);
+		if (port_ops && port_ops->create)
+			ret = port_ops->create(skb, port->dev,
+					       type, daddr, saddr, len);
+	}
+	rcu_read_unlock();
+	return ret;
+}
+
+static int team_header_parse(const struct sk_buff *skb,
+			     const struct net_device *team_dev,
+			     unsigned char *haddr)
+{
+	struct team *team = netdev_priv(team_dev);
+	const struct header_ops *port_ops;
+	struct team_port *port;
+	int ret = 0;
+
+	rcu_read_lock();
+	port = team_header_port_get_rcu(team, false);
+	if (port) {
+		port_ops = READ_ONCE(port->dev->header_ops);
+		if (port_ops && port_ops->parse)
+			ret = port_ops->parse(skb, port->dev, haddr);
+	}
+	rcu_read_unlock();
+	return ret;
+}
+
+static const struct header_ops team_header_ops = {
+	.create		= team_header_create,
+	.parse		= team_header_parse,
+};
+
 static void team_setup_by_port(struct net_device *dev,
 			       struct net_device *port_dev)
 {
@@ -2066,7 +2128,8 @@ static void team_setup_by_port(struct net_device *dev,
 	if (port_dev->type == ARPHRD_ETHER)
 		dev->header_ops	= team->header_ops_cache;
 	else
-		dev->header_ops	= port_dev->header_ops;
+		dev->header_ops	= port_dev->header_ops ?
+				  &team_header_ops : NULL;
 	dev->type = port_dev->type;
 	dev->hard_header_len = port_dev->hard_header_len;
 	dev->needed_headroom = port_dev->needed_headroom;
-- 
2.43.0

[PATCH net v3 2/2] selftests: team: add non-Ethernet header_ops reproducer

[Jiayuan Chen]

From: Jiayuan Chen <jiayuan.chen@shopee.com>

Add a team selftest that sets up:
  g0 (gre) -> b0 (bond) -> t0 (team)

and triggers IPv6 traffic on t0. This reproduces the non-Ethernet
header_ops confusion scenario and protects against regressions in stacked
team/bond/gre configurations.

Using this script, the panic reported by syzkaller can be reproduced [1].

After the fix:

  # ./non_ether_header_ops.sh
  PASS: non-Ethernet header_ops stacking did not crash

[1] https://syzkaller.appspot.com/bug?extid=3d8bc31c45e11450f24c

Cc: Jiayuan Chen <jiayuan.chen@linux.dev>
Signed-off-by: Jiayuan Chen <jiayuan.chen@shopee.com>
---
 .../selftests/drivers/net/team/Makefile       |  1 +
 .../testing/selftests/drivers/net/team/config |  2 +
 .../drivers/net/team/non_ether_header_ops.sh  | 41 +++++++++++++++++++
 3 files changed, 44 insertions(+)
 create mode 100755 tools/testing/selftests/drivers/net/team/non_ether_header_ops.sh

diff --git a/tools/testing/selftests/drivers/net/team/Makefile b/tools/testing/selftests/drivers/net/team/Makefile
index 45a3e7ad3dcb..02d6f51d5a06 100644
--- a/tools/testing/selftests/drivers/net/team/Makefile
+++ b/tools/testing/selftests/drivers/net/team/Makefile
@@ -3,6 +3,7 @@
 
 TEST_PROGS := \
 	dev_addr_lists.sh \
+	non_ether_header_ops.sh \
 	options.sh \
 	propagation.sh \
 	refleak.sh \
diff --git a/tools/testing/selftests/drivers/net/team/config b/tools/testing/selftests/drivers/net/team/config
index 558e1d0cf565..5d36a22ef080 100644
--- a/tools/testing/selftests/drivers/net/team/config
+++ b/tools/testing/selftests/drivers/net/team/config
@@ -1,7 +1,9 @@
+CONFIG_BONDING=y
 CONFIG_DUMMY=y
 CONFIG_IPV6=y
 CONFIG_MACVLAN=y
 CONFIG_NETDEVSIM=m
+CONFIG_NET_IPGRE=y
 CONFIG_NET_TEAM=y
 CONFIG_NET_TEAM_MODE_ACTIVEBACKUP=y
 CONFIG_NET_TEAM_MODE_LOADBALANCE=y
diff --git a/tools/testing/selftests/drivers/net/team/non_ether_header_ops.sh b/tools/testing/selftests/drivers/net/team/non_ether_header_ops.sh
new file mode 100755
index 000000000000..948a43576bdc
--- /dev/null
+++ b/tools/testing/selftests/drivers/net/team/non_ether_header_ops.sh
@@ -0,0 +1,41 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# shellcheck disable=SC2154
+#
+# Reproduce the non-Ethernet header_ops confusion scenario with:
+#   g0 (gre) -> b0 (bond) -> t0 (team)
+#
+# Before the fix, direct header_ops inheritance in this stack could call
+# callbacks with the wrong net_device context and crash.
+
+lib_dir=$(dirname "$0")
+source "$lib_dir"/../../../net/lib.sh
+
+trap cleanup_all_ns EXIT
+
+setup_ns ns1
+
+ip -n "$ns1" link add d0 type dummy
+ip -n "$ns1" addr add 10.10.10.1/24 dev d0
+ip -n "$ns1" link set d0 up
+
+ip -n "$ns1" link add g0 type gre local 10.10.10.1
+ip -n "$ns1" link add b0 type bond mode active-backup
+ip -n "$ns1" link add t0 type team
+
+ip -n "$ns1" link set g0 master b0
+ip -n "$ns1" link set b0 master t0
+
+ip -n "$ns1" link set g0 up
+ip -n "$ns1" link set b0 up
+ip -n "$ns1" link set t0 up
+
+# IPv6 address assignment triggers MLD join reports that call
+# dev_hard_header() on t0, exercising the inherited header_ops path.
+ip -n "$ns1" -6 addr add 2001:db8:1::1/64 dev t0 nodad
+for i in $(seq 1 20); do
+	ip netns exec "$ns1" ping -6 -I t0 ff02::1 -c1 -W1 &>/dev/null || true
+done
+
+echo "PASS: non-Ethernet header_ops stacking did not crash"
+exit "$EXIT_STATUS"
-- 
2.43.0

Re: [PATCH net v3 0/2] team: fix header_ops type confusion and add selftest

[patchwork-bot+netdevbpf]

Hello:

This series was applied to netdev/net.git (main)
by Paolo Abeni <pabeni@redhat.com>:

On Fri, 20 Mar 2026 15:21:25 +0800 you wrote:
> Hi,
> 
> This patch series fixes a panic reported by syzkaller in the team/bond/gre
> stacked non-Ethernet configuration:
> https://syzkaller.appspot.com/bug?extid=3d8bc31c45e11450f24c
> 
> The first patch fixes the header_ops type confusion / parse recursion
> context issue in team. The second patch adds a selftest to reproduce the
> reported scenario and prevent regressions in the future.
> 
> [...]

Here is the summary with links:
  - [net,v3,1/2] team: fix header_ops type confusion with non-Ethernet ports
    https://git.kernel.org/netdev/net/c/425000dbf173
  - [net,v3,2/2] selftests: team: add non-Ethernet header_ops reproducer
    https://git.kernel.org/netdev/net/c/56063823b9f0

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html