CVE-2026-53300 in Linux
Summary
by MITRE • 06/26/2026
In the Linux kernel, the following vulnerability has been resolved:
net: enetc: fix NTMP DMA use-after-free issue
The AI-generated review reported a potential DMA use-after-free issue [1]. If netc_xmit_ntmp_cmd() times out and returns an error, the pending
command is not explicitly aborted, while ntmp_free_data_mem() unconditionally frees the DMA buffer. If the buffer has already been reallocated elsewhere, this may lead to silent memory corruption. Because the hardware eventually processes the pending command and perform a DMA write of the response to the physical address of the freed buffer.
To resolve this issue, this patch does the following modifications:
1. Convert cbdr->ring_lock from a spinlock to a mutex
The lock was originally a spinlock in case NTMP operations might be invoked from atomic context. After downstream support for all NTMP tables, no such usage has materialized. A mutex lock is now required because the driver now needs to reclaim used BDs and release associated DMA memory within the lock's context, while dma_free_coherent() might sleep.
2. Introduce software command BD (struct netc_swcbd)
The hardware write-back overwrites the addr and len fields of the BD, so the driver cannot rely on the hardware BD to free the associated DMA memory. The driver now maintains a software shadow BD storing the DMA buffer pointer, DMA address, and size. And netc_xmit_ntmp_cmd() only reclaims older BDs when the number of used BDs reaches NETC_CBDR_CLEAN_WORK (16). The software BD enables correct DMA memory release. With this, struct ntmp_dma_buf and ntmp_free_data_mem() are no longer needed and are removed.
3. Require callers to hold ring_lock across netc_xmit_ntmp_cmd()
netc_xmit_ntmp_cmd() releases the ring_lock before the caller finishes consuming the response. At this point, if a concurrent thread submits a new command, it may trigger ntmp_clean_cbdr() and free the DMA buffer while it is still in use. Move ring_lock ownership to the caller to ensure the response buffer cannot be reclaimed prematurely. So the helpers ntmp_select_and_lock_cbdr() and ntmp_unlock_cbdr() are added.
These changes eliminate the DMA use-after-free condition and ensure safe and consistent BD reclamation and DMA buffer lifecycle management.
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Analysis
by VulDB Data Team • 06/26/2026
The vulnerability described in this CVE relates to a DMA use-after-free issue within the Linux kernel's enetc network driver, specifically affecting the NTMP (Network Table Management Protocol) functionality. This flaw represents a critical memory safety concern that could potentially lead to system instability or security exploitation. The issue arises from improper handling of DMA buffer lifecycle management during command execution, where hardware operations interact with memory that has already been freed by the software component.
The technical root cause stems from the interaction between the netc_xmit_ntmp_cmd() function and the ntmp_free_data_mem() cleanup routine. When a transmission command times out and returns an error condition, the system fails to explicitly abort the pending command before proceeding with memory deallocation. This creates a race condition where the DMA buffer gets freed unconditionally by ntmp_free_data_mem(), while the hardware may later process the same command and perform a DMA write operation to the physical address of the already-freed memory region. This scenario results in silent memory corruption that can persist undetected until system instability manifests.
The patch implementation addresses this vulnerability through three primary modifications that fundamentally restructure how the driver manages command buffers and synchronization. First, the conversion of cbdr->ring_lock from a spinlock to a mutex represents a crucial architectural change that acknowledges the evolving requirements of the driver. Originally designed to support atomic context operations, the spinlock was no longer necessary after downstream support for all NTMP tables was completed. The mutex implementation becomes essential because it allows for safe execution of dma_free_coherent() calls within the lock's critical section, as this function may sleep during memory deallocation operations that would be incompatible with spinlock behavior.
The introduction of software command BD structures (struct netc_swcbd) creates a more robust mechanism for tracking DMA buffer ownership and lifecycle management. This change addresses the fundamental problem that hardware write-back operations overwrite the address and length fields of the BD structure, making it unreliable for memory cleanup purposes. By maintaining a separate software shadow BD that stores the DMA buffer pointer, physical address, and size information, the driver can accurately determine when and how to release associated memory resources. This approach eliminates the need for the struct ntmp_dma_buf and ntmp_free_data_mem() components that were contributing to the vulnerability.
The third critical modification involves requiring callers to maintain ring_lock ownership throughout the complete execution of netc_xmit_ntmp_cmd(), including response processing. This change prevents a race condition where concurrent threads could submit new commands while an existing command's response is still being consumed, potentially triggering ntmp_clean_cbdr() and freeing memory that remains in use. The introduction of helper functions ntmp_select_and_lock_cbdr() and ntmp_unlock_cbdr() formalizes this locking pattern and ensures consistent protection across all command execution paths. This approach aligns with security best practices for concurrent access control and memory management, addressing potential issues identified under CWE-415 and CWE-416 categories that relate to double-free conditions and use-after-free vulnerabilities.
The overall impact of these changes represents a comprehensive solution that eliminates the DMA use-after-free condition while maintaining system performance and reliability. The modifications ensure proper BD reclamation and DMA buffer lifecycle management through improved synchronization mechanisms, software state tracking, and consistent locking practices. This vulnerability resolution demonstrates the importance of careful memory management in kernel drivers, particularly when dealing with hardware interaction patterns that involve DMA operations and concurrent access scenarios. The solution aligns with ATT&CK framework considerations for privilege escalation and system stability maintenance, as it prevents potential exploitation through memory corruption vulnerabilities that could lead to unauthorized system access or denial-of-service conditions.