Bug 2540379 (CVE-2026-97481)

Summary:	CVE-2026-97481 kernel: serial: 8250: fix possible ISR soft lockup
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security <prodsec-ir-bot>
Status:	NEW ---	QA Contact:
Severity:	low	Docs Contact:
Priority:	low
Version:	unspecified	CC:	akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	---
Doc Text:	A flaw was found in the Linux kernel's 8250 serial port driver. An attacker communicating over the serial interface can cause a Denial of Service (DoS) by flooding the port with messages during the system startup phase. Due to missing error handling for First-In, First-Out (FIFO) buffer interrupts, the system repeatedly re-triggers the interrupt without clearing it. This results in a continuous loop within the interrupt service routine (ISR), leading to a kernel soft lockup and system unresponsiveness.	Story Points:	---
Clone Of:		Environment:
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Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-09-24 16:35:46 UTC

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 IRQ_HANDLED 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.

Comment 1 Mauro Matteo Cascella 2026-09-29 19:23:16 UTC

Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-97481.mbox