Linux Kernel EUVD-2026-58906

The DesignWare Enhanced DMA (dw-edma) engine is a hardware IP block frequently embedded in PCIe endpoint controllers and used on platforms where the Linux dmaengine subsystem manages channel setup via the dw_edma_v0_core_start() function. The DONE_INT_MASK and ABORT_INT_MASK registers are memory-mapped hardware registers shared across all DMA channels on a given controller instance. Because the driver performed a non-atomic read-modify-write sequence - reading the current mask, ORing in or clearing the relevant channel bit, then writing back - two kernel threads or interrupt contexts racing to start separate DMA channels could read the same stale register value simultaneously, each write back a partial update, and thereby silently drop interrupt mask bits for one or both channels. This is a classic CWE-362 (Concurrent Execution Using Shared Resource with Improper Synchronization) pattern at the MMIO register level. The fix serializes the read-modify-write with a spinlock added to the dw_edma structure, preventing simultaneous access.