Medium [CVE-2026-53300] fix NTMP DMA use-after-free issue

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.