CVE-2026-72476
Summary
by MITRE • 08/15/2026
In the Linux kernel, the following vulnerability has been resolved:
dmaengine: Fix possible use after free
In dma_release_channel(), check chan->device->privatecnt after call dma_chan_put(). However, dma_chan_put() call dma_device_put() which could release the last reference of the device if the DMA provider is already gone and hence free it.
Fixes it by moving dma_chan_put() after the check.
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Analysis
by VulDB Data Team • 08/15/2026
This vulnerability exists within the linux kernel's dmaengine subsystem where a use-after-free condition can occur during channel cleanup operations. The flaw manifests in the dma_release_channel function where the code attempts to access chan->device->privatecnt after calling dma_chan_put(). This ordering issue creates a race condition that can lead to accessing freed memory structures. When dma_chan_put() executes, it internally calls dma_device_put() which may decrement the device reference count and ultimately release the entire device structure if the DMA provider has already been removed from the system. The vulnerability stems from improper resource management sequencing where the device reference is released before the subsequent access to device-specific data structures occurs.
The technical implementation of this flaw demonstrates a classic use-after-free vulnerability pattern that aligns with CWE-416 and CWE-125 categories. The issue occurs when the kernel attempts to maintain reference counting for DMA channels and their associated devices, but fails to properly sequence the operations during cleanup. The dma_release_channel function exhibits problematic temporal coupling between resource release and data access operations, creating a window where memory that was freed by dma_device_put() can still be referenced through chan->device->privatecnt. This scenario represents a fundamental flaw in kernel memory management where the ordering of reference counting operations directly impacts system stability.
The operational impact of this vulnerability extends beyond simple memory corruption to potentially enable privilege escalation or system instability. When an attacker can trigger the specific sequence leading to the use-after-free condition, they may be able to manipulate the freed memory contents or cause the kernel to execute code from corrupted data structures. This type of vulnerability is particularly dangerous in kernel space because it operates at the highest privilege level and can compromise the entire system. The timing requirements for exploitation make this a sophisticated attack vector that typically requires precise control over DMA channel operations and device removal sequences.
The fix implemented addresses this issue by reordering the operations within the dma_release_channel function to ensure proper resource management sequence. By moving dma_chan_put() to execute after the check of chan->device->privatecnt, the vulnerability is resolved through correct temporal ordering that prevents access to freed memory structures. This mitigation aligns with established kernel security practices for reference counting and memory management. The solution follows ATT&CK technique T1068 by addressing a privilege escalation vector through proper resource handling. The change ensures that device references remain valid during all necessary access operations, maintaining the integrity of the DMA subsystem and preventing potential exploitation scenarios that could otherwise lead to system compromise or denial of service conditions.