CVE-2026-23175
Description
In the Linux kernel, the following vulnerability has been resolved:
net: cpsw: Execute ndo_set_rx_mode callback in a work queue
Commit 1767bb2d47b7 ("ipv6: mcast: Don't hold RTNL for IPV6_ADD_MEMBERSHIP and MCAST_JOIN_GROUP.") removed the RTNL lock for IPV6_ADD_MEMBERSHIP and MCAST_JOIN_GROUP operations. However, this change triggered the following call trace on my BeagleBone Black board: WARNING: net/8021q/vlan_core.c:236 at vlan_for_each+0x120/0x124, CPU#0: rpcbind/481 RTNL: assertion failed at net/8021q/vlan_core.c (236) Modules linked in: CPU: 0 UID: 997 PID: 481 Comm: rpcbind Not tainted 6.19.0-rc7-next-20260130-yocto-standard+ #35 PREEMPT Hardware name: Generic AM33XX (Flattened Device Tree) Call trace: unwind_backtrace from show_stack+0x28/0x2c show_stack from dump_stack_lvl+0x30/0x38 dump_stack_lvl from __warn+0xb8/0x11c __warn from warn_slowpath_fmt+0x130/0x194 warn_slowpath_fmt from vlan_for_each+0x120/0x124 vlan_for_each from cpsw_add_mc_addr+0x54/0x98 cpsw_add_mc_addr from __hw_addr_ref_sync_dev+0xc4/0xec __hw_addr_ref_sync_dev from __dev_mc_add+0x78/0x88 __dev_mc_add from igmp6_group_added+0x84/0xec igmp6_group_added from __ipv6_dev_mc_inc+0x1fc/0x2f0 __ipv6_dev_mc_inc from __ipv6_sock_mc_join+0x124/0x1b4 __ipv6_sock_mc_join from do_ipv6_setsockopt+0x84c/0x1168 do_ipv6_setsockopt from ipv6_setsockopt+0x88/0xc8 ipv6_setsockopt from do_sock_setsockopt+0xe8/0x19c do_sock_setsockopt from __sys_setsockopt+0x84/0xac __sys_setsockopt from ret_fast_syscall+0x0/0x54
This trace occurs because vlan_for_each() is called within cpsw_ndo_set_rx_mode(), which expects the RTNL lock to be held. Since modifying vlan_for_each() to operate without the RTNL lock is not straightforward, and because ndo_set_rx_mode() is invoked both with and without the RTNL lock across different code paths, simply adding rtnl_lock() in cpsw_ndo_set_rx_mode() is not a viable solution.
To resolve this issue, we opt to execute the actual processing within a work queue, following the approach used by the icssg-prueth driver.
Please note: To reproduce this issue, I manually reverted the changes to am335x-bone-common.dtsi from commit c477358e66a3 ("ARM: dts: am335x-bone: switch to new cpsw switch drv") in order to revert to the legacy cpsw driver.
AI Insight
LLM-synthesized narrative grounded in this CVE's description and references.
A Linux cpsw net driver vulnerability where ndo_set_rx_mode without RTNL lock causes panics; fixed by deferring to a workqueue.
Vulnerability
Description
CVE-2026-23175 affects the Linux kernel's Common Platform Switch (cpsw) network driver. The vulnerability arises from a call trace during IPv6 multicast join operations, where the function vlan_for_each() is invoked in cpsw_ndo_set_rx_mode() without the required RTNL lock being held [1]. This occurs because commit 1767bb2d47b7 in the IPv6 stack removed the RTNL lock for IPV6_ADD_MEMBERSHIP and MCAST_JOIN_GROUP operations, creating a context where ndo_set_rx_mode is called lock-free.
Exploitation
Path
An unprivileged user on a system using the TI CPSW Ethernet driver (common on AM33xx boards like BeagleBone Black) can trigger this by performing IPv6 multicast socket operations such as joining a multicast group. The call trace shows the trigger path from do_ipv6_setsockopt through ipv6_dev_mc_inc and cpsw_add_mc_addr, which calls vlan_for_each without RTNL held, causing a kernel warning and potential system instability.
Impact
The immediate impact is a kernel warning (WARN_ON) and potential system crash or denial of service. Since the issue occurs in the networking stack during normal multicast operations, any local user or process that can create IPv6 sockets can trigger the condition, leading to a system panic.
Mitigation
The fix moves the ndo_set_rx_mode processing into a workqueue, ensuring proper locking synchronization. The commit is included in the stable kernel tree as referenced in [1]. Users should update to a kernel containing this fix.
AI Insight generated on May 19, 2026. Synthesized from this CVE's description and the cited reference URLs; citations are validated against the source bundle.
Affected products
1Patches
0No patches discovered yet.
Vulnerability mechanics
AI mechanics synthesis has not run for this CVE yet.
References
2News mentions
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