UBUNTU-CVE-2026-98903: Medium severity ubuntu/linux vulnerability

In the Linux kernel, the following vulnerability has been resolved: mailbox: imx: Add a channel shutdown field sashiko complained about possible teardown problem. The scenario CPU 0 CPU 1 imxmuisr() imxmushutdown() imxmuxcrrmw(priv, IMXMURCR, 0, IMXMUxCRRIEn(priv->dcfg->type, cp->idx)); imxmuspecificrx() imxmuxcrrmw(priv, IMXMURCR, IMXMUxCRRIEn(priv->dcfg->type, 0), 0); freeirq() The RX event remains enabled because in this short window the RX event was disabled in ->shutdown() while the interrupt was active and then enabled again by the ISR while ->shutdown waited in freeirq(). This race requires timing and if happens can be problematic on shared handlers if the "removed" channel triggers an interrupt. In this case the irq-core will shutdown the interrupt with the "nobody cared" message. Introduce imxmuconpriv::shutdown to signal that the channel is shutting down. This flag is set with the lock held (by imxmuxcrclrshut()). The unmask side uses imxmuxcrsetact() which only enables the event if the channel has not been shutdown and serialises on the same lock.