Bug 2555239 (CVE-2026-98821)

Summary:	CVE-2026-98821 kernel: block: reject polled dio with user integrity metadata
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 block layer. A local user could exploit this vulnerability to cause a denial of service (DoS) by initiating polled direct I/O operations combined with user integrity metadata. Because the kernel improperly attempts to poll integrity metadata as standard block I/O request structures, an invalid pointer dereference occurs, resulting in a system crash.	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 2026-10-18 16:03:58 UTC

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

block: reject polled dio with user integrity metadata

IOCB_HAS_METADATA leaves iocb->private as a uio_meta, while
iocb_bio_iopoll() expects a bio. Since 2729a60bbfb9, metadata I/O
always uses __blkdev_direct_IO(), which never publishes the bio for
polling, so IOPOLL calls bio_poll() on the uio_meta.

Reproducer: io_uring IOPOLL plus a PI attribute on an integrity device
(scsi_debug dif=1 dix=1). KASAN reports:

  Oops: general protection fault, probably for non-canonical
  address 0xdffffc0000000004
  KASAN: null-ptr-deref in range
  [0x0000000000000020-0x0000000000000027]
  RIP: 0010:bio_poll+0x9d/0x4b0
  Call Trace:
   iocb_bio_iopoll+0x5b/0x80
   io_uring_classic_poll+0xf3/0x140
   io_do_iopoll+0x4e3/0xc00
   io_iopoll_check+0x275/0x560
   __do_sys_io_uring_enter+0x2e5/0x720

Return -EOPNOTSUPP when HIPRI is combined with user metadata.