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Start for freedmaengine: mmp_pdma: Fix race condition in mmp_pdma_residue()
In the Linux kernel, the following vulnerability has been resolved:
dmaengine: mmp_pdma: Fix race condition in mmp_pdma_residue()
Add proper locking in mmp_pdma_residue() to prevent use-after-free when accessing descriptor list and descriptor contents.
The race occurs when multiple threads call tx_status() while the tasklet on another CPU is freeing completed descriptors:
CPU 0 CPU 1
mmp_pdma_tx_status() mmp_pdma_residue() -> NO LOCK held list_for_each_entry(sw, ..) DMA interrupt dma_do_tasklet() -> spin_lock(&desc_lock) list_move(sw->node, ...) spin_unlock(&desc_lock) | dma_pool_free(sw) <- FREED! -> access sw->desc <- UAF!
This issue can be reproduced when running dmatest on the same channel with multiple threads (threads_per_chan > 1).
Fix by protecting the chain_running list iteration and descriptor access with the chan->desc_lock spinlock.