published August 15, 2026
In the Linux kernel, the following vulnerability has been resolved:
dmaengine: dma-axi-dmac: use DMA pool to manange DMA descriptor
For architectures like Microblaze or arm64 (where this IP is used),
DMA_DIRECT_REMAP is set which means that dma_alloc_coherent() might
remap (and hence vmalloc()) some memory. This became visible in a design
where dma_direct_use_pool() is not possible.
With the above, when calling dma_free_coherent(), vunmap() would be
called from softirq context and thus leading to a BUG().
To fix it, use a dma pool that is allocated in
.device_alloc_chan_resources() and allocate blocks from it. The key
point is that now dma_pool_free() is used in axi_dmac_free_desc() to
free the blocks and that just frees the blocks from the pool in the
sense they can be used again. In other words, no actual call to
dma_free_coherent() happens. That only happens when destroying the pool
in axi_dmac_free_chan_resources() which does not happen in any interrupt
context.