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dmaengine: mmp_pdma: Fix race condition in mmp_pdma_residue()

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[ Upstream commit a143545855 ]

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 <lijuan@linux.spacemit.com>
Signed-off-by: Guodong Xu <guodong@riscstar.com>
Link: https://patch.msgid.link/20251216-mmp-pdma-race-v1-1-976a224bb622@riscstar.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
[ Minor context conflict resolved. ]
Signed-off-by: Wenshan Lan <jetlan9@163.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Guodong Xu
2026-03-25 11:06:00 +01:00
committed by Greg Kroah-Hartman
parent 33743ec667
commit eba0c75670
1 changed files with 6 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files
drivers/dma/mmp_pdma.c
+6
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@@ -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;
}