Affected: Linux

In the Linux kernel, the following vulnerability has been resolved:

crypto: qat - fix DMA transfer direction

When CONFIG_DMA_API_DEBUG is selected, while running the crypto self test on the QAT crypto algorithms, the function add_dma_entry() reports a warning similar to the one below, saying that overlapping mappings are not supported. This occurs in tests where the input and the output scatter list point to the same buffers (i.e. two different scatter lists which point to the same chunks of memory).

The logic that implements the mapping uses the flag DMA_BIDIRECTIONAL for both the input and the output scatter lists which leads to overlapped write mappings. These are not supported by the DMA layer.

Fix by specifying the correct DMA transfer directions when mapping buffers. For in-place operations where the input scatter list matches the output scatter list, buffers are mapped once with DMA_BIDIRECTIONAL, otherwise input buffers are mapped using the flag DMA_TO_DEVICE and output buffers are mapped with DMA_FROM_DEVICE. Overlapping a read mapping with a write mapping is a valid case in dma-coherent devices like QAT. The function that frees and unmaps the buffers, qat_alg_free_bufl() has been changed accordingly to the changes to the mapping function.

DMA-API: 4xxx 0000:06:00.0: cacheline tracking EEXIST, overlapping mappings aren't supported WARNING: CPU: 53 PID: 4362 at kernel/dma/debug.c:570 add_dma_entry+0x1e9/0x270 ... Call Trace: dma_map_page_attrs+0x8…