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Commit 3e4543bf authored by Pierre-Yves MORDRET's avatar Pierre-Yves MORDRET Committed by Vinod Koul
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dmaengine: stm32-dmamux: fix a potential buffer overflow 



The bitfield dma_inuse is allocated of size dma_requests bits, thus a
valid bit address is from 0 to (dma_requests - 1).
When find_first_zero_bit() fails, it returns dma_requests as invalid
address.
Using such address for the following set_bit() is incorrect and, if
dma_requests is a multiple of BITS_PER_LONG, it will cause a buffer
overflow.
Currently this driver is only used in DT stm32h743.dtsi where a safe value
dma_requests=16 is not triggering the buffer overflow.

Fixed by checking the return value of find_first_zero_bit() _before_
using it.

Signed-off-by: default avatarAntonio Borneo <borneo.antonio@gmail.com>
Signed-off-by: default avatarPierre-Yves MORDRET <pierre-yves.mordret@st.com>
Signed-off-by: default avatarVinod Koul <vinod.koul@intel.com>
parent 0c8efd61

drivers/dma/stm32-dmamux.c

+6 −3
Original line number Diff line number Diff line
@@ -118,14 +118,15 @@ static void *stm32_dmamux_route_allocate(struct of_phandle_args *dma_spec, 
	spin_lock_irqsave(&dmamux->lock, flags);

	mux->chan_id = find_first_zero_bit(dmamux->dma_inuse,

					   dmamux->dma_requests);

	set_bit(mux->chan_id, dmamux->dma_inuse);

	spin_unlock_irqrestore(&dmamux->lock, flags);



	if (mux->chan_id == dmamux->dma_requests) {

		spin_unlock_irqrestore(&dmamux->lock, flags);

		dev_err(&pdev->dev, "Run out of free DMA requests\n");

		ret = -ENOMEM;

		goto error;

		goto error_chan_id;

	}

	set_bit(mux->chan_id, dmamux->dma_inuse);

	spin_unlock_irqrestore(&dmamux->lock, flags);



	/* Look for DMA Master */

	for (i = 1, min = 0, max = dmamux->dma_reqs[i];
@@ -173,6 +174,8 @@ static void *stm32_dmamux_route_allocate(struct of_phandle_args *dma_spec, 


error:

	clear_bit(mux->chan_id, dmamux->dma_inuse);



error_chan_id:

	kfree(mux);

	return ERR_PTR(ret);

}