CVE-2026-74255tipc: fix UAF in tipc_l2_send_msg()

Official description

In the Linux kernel, the following vulnerability has been resolved: tipc: fix UAF in tipc_l2_send_msg() Syzbot reported a slab-use-after-free in ipvlan_hard_header() when called from tipc_l2_send_msg(). The root cause is that tipc_disable_l2_media() calls synchronize_net() while b->media_ptr is still valid. This allows concurrent RCU readers to obtain the device pointer after synchronize_net() has finished. The pointer is cleared later in bearer_disable(), but without any subsequent synchronization, allowing the device to be freed while still in use by readers. Fix this by clearing b->media_ptr in tipc_disable_l2_media() before calling synchronize_net(). This is safe to do now because the call order in bearer_disable() was reversed in 0d051bf93c06 ("tipc: make bearer packet filtering generic") to call tipc_node_delete_links() (which needs the pointer) before disable_media(). https: //lore.kernel.org/netdev/6a2c1007.428ffe26.258b27.015d.GAE@google.com/T/#u

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/609ced2301be1df7e7ed2ef47d1d916674e6ba3b
• https://git.kernel.org/stable/c/71aafa16d79b107b33837f60b6cbc7d0cb8c5708
• https://git.kernel.org/stable/c/f4002f1c669cc02e3763f479fc25ff1dfa9e2420
• https://git.kernel.org/stable/c/50ff092633b06382e5091dd5b093ce943d4ac2f9
• https://git.kernel.org/stable/c/aef12b5ce793dea6b3a97a58fd0f946000ae8945
• https://git.kernel.org/stable/c/0d8a12d7143126afdf9fbe2e3d438650dd6603ed
• https://git.kernel.org/stable/c/35e0297a93c3c34a3924eeef816c03504e3ab5c5
• https://git.kernel.org/stable/c/f4c3d89fc986b0da196ddfc6cfe0ea5d5d08bec6