CVE-2025-71221

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.