From eba0c75670c022cb1f948600db972524bcfe8166 Mon Sep 17 00:00:00 2001 From: Guodong Xu Date: Sat, 28 Feb 2026 14:47:36 +0800 Subject: [PATCH] dmaengine: mmp_pdma: Fix race condition in mmp_pdma_residue() [ Upstream commit a143545855bc2c6e1330f6f57ae375ac44af00a7 ] 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. Signed-off-by: Juan Li Signed-off-by: Guodong Xu Link: https://patch.msgid.link/20251216-mmp-pdma-race-v1-1-976a224bb622@riscstar.com Signed-off-by: Vinod Koul [ Minor context conflict resolved. ] Signed-off-by: Wenshan Lan Signed-off-by: Greg Kroah-Hartman --- drivers/dma/mmp_pdma.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/dma/mmp_pdma.c b/drivers/dma/mmp_pdma.c index ebdfdcbb4f7a..046358e328eb 100644 --- a/drivers/dma/mmp_pdma.c +++ b/drivers/dma/mmp_pdma.c @@ -764,6 +764,7 @@ static unsigned int mmp_pdma_residue(struct mmp_pdma_chan *chan, { struct mmp_pdma_desc_sw *sw; u32 curr, residue = 0; + unsigned long flags; bool passed = false; bool cyclic = chan->cyclic_first != NULL; @@ -779,6 +780,8 @@ static unsigned int mmp_pdma_residue(struct mmp_pdma_chan *chan, else curr = readl(chan->phy->base + DSADR(chan->phy->idx)); + spin_lock_irqsave(&chan->desc_lock, flags); + list_for_each_entry(sw, &chan->chain_running, node) { u32 start, end, len; @@ -822,6 +825,7 @@ static unsigned int mmp_pdma_residue(struct mmp_pdma_chan *chan, continue; if (sw->async_tx.cookie == cookie) { + spin_unlock_irqrestore(&chan->desc_lock, flags); return residue; } else { residue = 0; @@ -829,6 +833,8 @@ static unsigned int mmp_pdma_residue(struct mmp_pdma_chan *chan, } } + spin_unlock_irqrestore(&chan->desc_lock, flags); + /* We should only get here in case of cyclic transactions */ return residue; }