CVE-2026-98344

A flaw was found in the Linux kernel's DMA (Direct Memory Access) engine subsystem. This vulnerability can lead to a Denial of Service (DoS) when a local user triggers concurrent channel acquisition and release operations. Because the dma_chan_put() function unconditionally decrements device reference counts during fast-path operations, the counter can prematurely drop to zero, causing subsequent DMA channel lookups to fail.

A Low impact local denial of service flaw was found in the Linux kernel DMA engine subsystem shipped in Red Hat Enterprise Linux, RHIVOS, and the RHEL CoreOS kernels used by Red Hat OpenShift. The dma_chan_get() function only takes a reference on the DMA device on the slow path (when a channel has no existing clients), while dma_chan_put() drops that reference unconditionally. As a result, every fast-path channel get/put pair releases one extra device reference. A local user able to trigger concurrent DMA channel acquisition and release operations can drive the device reference count down to zero while the provider module is still loaded, after which dma_find_channel() can no longer return the affected channel and DMA-dependent functionality becomes unavailable. Confidentiality and integrity are not affected.

The CVSS:3.1 base score is 5.5 (AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H, moderate). Red Hat rates the impact of this flaw as Low because exploitation requires local access with low privileges and depends on the specific combination of a non-private DMA provider that has a persistent client holding a channel while another client repeatedly cycles channel acquisition and release.

Red Hat Enterprise Linux 7 (kernel and kernel-rt) is not affected because the vulnerable code is not present in that code base; Red Hat Enterprise Linux 6 Extended Lifecycle Support is out of support scope. For the affected products, the fix has been deferred to a future update due to the Low impact rating. The residual risk of deferring the fix is limited to local denial of service affecting DMA-dependent subsystems in configurations that meet the preconditions described above.

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.