Bug 2535270 (CVE-2026-89906)

Summary:	CVE-2026-89906 kernel: LoongArch: BPF: Refactor jump offset calculation in tail call
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security <prodsec-ir-bot>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
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 Berkeley Packet Filter (BPF) component for LoongArch architecture. An issue with the jump offset calculation in BPF tail calls, caused by using a stale prior-pass code stride, can lead to incorrect branch offsets. This vulnerability could result in soft lockups under extra Just-In-Time (JIT) passes, potentially causing a Denial of Service (DoS) for the system.	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 2026-09-16 11:44:59 UTC

In the Linux kernel, the following vulnerability has been resolved:

LoongArch: BPF: Refactor jump offset calculation in tail call

The old macro-based jmp_offset calculation derives the jump distance
from a stale prior-pass code stride, which can lead to wrong branch
offsets and soft lockups under extra JIT passes.

Fix this by calculating the offset directly on the absolute target:
"ctx->offset[insn + 1] - ctx->idx".

To avoid a false 16-bit range check abort during size estimation, add
a "ctx->image == NULL" guard to inject a safe dummy offset.