Bug 2528540 (CVE-2026-80788)

Summary:	CVE-2026-80788 kernel: nvmet-tcp: Do not WARN on remotely-controlled oversized SGL allocations
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
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 nvmet-tcp component. A remote attacker can send a specially crafted command with an oversized Scatter-Gather List (SGL) allocation. This can lead to an excessive memory allocation, triggering a kernel warning. On systems configured to panic on warnings, this could result in a denial of service.	Story Points:	---
Clone Of:		Environment:
Last Closed:		Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-09-04 15:32:05 UTC

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

nvmet-tcp: Do not WARN on remotely-controlled oversized SGL allocations

When fuzzing the nvme target code, I tripped a kernel warning in
nvmet_tcp_map_data() because the length passed into the allocator is
controlled by the remote initiator.

A remote initiator that sends a command with an SGL claiming a huge
number, can create a scatterlist and iovec allocation of over 1 million
entries, which causes the backing kmalloc call to exceed MAX_PAGE_ORDER
and then the page allocator will trip on a WARN_ON_ONCE_GFP() message:

  WARNING: mm/page_alloc.c:5280 __alloc_frozen_pages_noprof
  Workqueue: nvmet_tcp_wq nvmet_tcp_io_work
  ...
  sgl_alloc_order
  nvmet_tcp_map_data
  nvmet_tcp_try_recv_pdu

As it's never good to trip a kernel warning remotely due to many systems
having panic-on-warn enabled, let's silence it by just add GFP_NOWARN to
the allocation flags.

Comment 1 Mauro Matteo Cascella 2026-09-04 18:03:03 UTC

Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-80788.mbox