From 92f853f0645aebf1d05d333e97ab7c342ace1892 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Nuno=20S=C3=A1?= Date: Fri, 24 Apr 2026 18:40:14 +0100 Subject: [PATCH] dmaengine: Fix possible use after free MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit In dma_release_channel(), check chan->device->privatecnt after call dma_chan_put(). However, dma_chan_put() call dma_device_put() which could release the last reference of the device if the DMA provider is already gone and hence free it. Fixes it by moving dma_chan_put() after the check. Fixes: 0f571515c332 ("dmaengine: Add privatecnt to revert DMA_PRIVATE property") Signed-off-by: Nuno Sá Reviewed-by: Frank Li Link: https://patch.msgid.link/20260424-dma-dmac-handle-vunmap-v4-1-90f43412fdc0@analog.com Signed-off-by: Vinod Koul --- drivers/dma/dmaengine.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c index 405bd2fbb4a3..9049171df857 100644 --- a/drivers/dma/dmaengine.c +++ b/drivers/dma/dmaengine.c @@ -905,11 +905,12 @@ void dma_release_channel(struct dma_chan *chan) mutex_lock(&dma_list_mutex); WARN_ONCE(chan->client_count != 1, "chan reference count %d != 1\n", chan->client_count); - dma_chan_put(chan); /* drop PRIVATE cap enabled by __dma_request_channel() */ if (--chan->device->privatecnt == 0) dma_cap_clear(DMA_PRIVATE, chan->device->cap_mask); + dma_chan_put(chan); + if (chan->slave) { sysfs_remove_link(&chan->dev->device.kobj, DMA_SLAVE_NAME); sysfs_remove_link(&chan->slave->kobj, chan->name);