CVE-2026-98347IB/IPoIB: Avoid restoring OPER_UP after multicast flush

Official description

In the Linux kernel, the following vulnerability has been resolved: IB/IPoIB: Avoid restoring OPER_UP after multicast flush ipoib_ib_dev_flush_light() temporarily clears IPOIB_FLAG_OPER_UP to prevent multicast joins while ipoib_mcast_dev_flush() is running, and restores the flag afterwards if it was previously set. This restore races with ipoib_ib_dev_down(). If the interface is brought down while the flush is in progress, ipoib_ib_dev_down() clears IPOIB_FLAG_OPER_UP, but the flush path may set it again after the device has already gone down. Since commit 894021a75291 ("IB/ipoib: Make the carrier_on_task race aware"), ipoib_mcast_carrier_on_task() relies on IPOIB_FLAG_OPER_UP being cleared to terminate its rtnl_trylock() retry loop. If the flag is left set after shutdown, the workqueue retries forever, causing teardown to deadlock when ipoib_ndo_uninit() waits in destroy_workqueue() while holding RTNL. Instead of overloading IPOIB_FLAG_OPER_UP to block multicast joins during a light flush, introduce a dedicated IPOIB_FLAG_MCAST_FLUSH flag. Use it together with IPOIB_FLAG_OPER_UP to determine whether multicast joins are allowed, avoiding the race with device shutdown.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/f973769fb7cb33ba0d4a64b7dcfee0cabaead938
• https://git.kernel.org/stable/c/b72f38929f4b5aa83161fd3b22a7327207e51ec5
• https://git.kernel.org/stable/c/1b11e4b55b41d9e69a8e8d07622614202e2eaca9
• https://git.kernel.org/stable/c/326f7d34bd7e64de535566b65c0533b640df5a81
• https://git.kernel.org/stable/c/5ad925d45f28464a5e043c9620880bb6a030da89
• https://git.kernel.org/stable/c/188b334a6db36a8e0bfaaf59bc4020639a0f3aad
• https://git.kernel.org/stable/c/1ff3add37c329704ec46181b4ae4f00f9f16ce6f
• https://git.kernel.org/stable/c/9a141d3dc869d18b2eab35e999f4790a9b84e40f