CVE-2026-97551

A flaw was found in the Linux kernel's XFS file system. A local user can trigger a Denial of Service (DoS) by forcing an unexpected filesystem shutdown. When updating parent pointer attributes, the kernel fails to properly initialize the block reservation counter, causing an integer underflow during storage space allocation. Under constrained storage conditions, this miscalculation leads to an unhandled allocation error that forces the filesystem to shut down.

A flaw in the Linux kernel's XFS filesystem allows a local user to cause a denial of service by forcing an unexpected filesystem shutdown. When an XFS parent pointer attribute is added or replaced, xfs_parent_da_args_init() leaves the block reservation counter (args->total) uninitialized at zero; if the attribute fork must grow, xfs_da_grow_inode_int() subtracts from that counter, causing a 32-bit integer underflow that wraps to ~0U and defeats the free-space check in xfs_alloc_space_available(). When this coincides with an allocation group that has exactly zero available blocks, the allocation is clamped and returns -ENOSPC, which xfs_defer_finish_noroll() escalates to a filesystem shutdown. Red Hat assesses this flaw as Moderate (CVSS 3.1: 5.5, AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H): a local user with write access to an XFS filesystem with parent pointers enabled can trigger the shutdown under specific low-free-space conditions, but only the availability of the local filesystem is affected, with no demonstrated confidentiality, integrity, or privilege-escalation impact.

The vulnerable parent pointer code is not present in Red Hat Enterprise Linux 6, 7, and 8, in earlier RHEL 9 minor streams (RHEL 9.2, 9.4, and 9.6, including the corresponding kernel-rt packages), or in OpenShift Container Platform releases built on those kernels, so those products are not affected. The affected Red Hat Enterprise Linux 9 (9.8 and later), RHEL 10, Red Hat In-Vehicle OS, and OpenShift Container Platform 4.22 and later streams carry a DEFER resolution: because this is a moderate-severity local denial of service, the fix will be delivered through a future scheduled update rather than an immediate z-stream erratum. The residual risk of the deferral is limited to local denial of service against XFS filesystems with parent pointers enabled.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.