CVE-2026-97481: serial: 8250: fix possible ISR soft lockup
In the Linux kernel, the following vulnerability has been resolved:
serial: 8250: fix possible ISR soft lockup
There are rare cases in which the host gets stuck in the ISR because it is flooded with messages during the startup phase.
The reason for the soft lockup in the ISR is the missing FIFO error IRQ (FIFOE) handling. Not handling it and reporting IRQHANDLED triggers the IRQ immediately again.
Fix this by adding a check for the FIFOE status and clearing the FIFO if no data is ready (DR).
This behavior was observed on an AM62L device which uses the OMAP 8250 driver. Fix it for all 8250 drivers, since the OMAP driver's special IRQ setup handling may trigger this behavior more frequently, but it is not ensured that other 8250 drivers aren't affected.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Compensating control
For all 8250 drivers, including the OMAP 8250 driver, add a check for FIFOE status and clear the FIFO when no data is ready (DR) to prevent the ISR soft lockup.
Event History
Frequently Asked Questions
Which systems are most likely to be affected?
The issue was observed on an AM62L device using the OMAP 8250 driver. The fix applies to all 8250 drivers because other 8250-based drivers may also be affected, although the OMAP driver's IRQ setup may make the condition more likely.
When does the soft lockup occur?
It can occur during startup when the host is flooded with messages and a FIFO error IRQ is not handled. Reporting the interrupt as handled without clearing the FIFO when no data is ready can cause the IRQ to immediately retrigger and leave the host stuck in the ISR.