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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: Antonio Borneo <borneo.antonio@gmail.com> Signed-off-by: Pierre-Yves MORDRET <pierre-yves.mordret@st.com> Signed-off-by: Vinod Koul <vinod.koul@intel.com>
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@ -118,14 +118,15 @@ static void *stm32_dmamux_route_allocate(struct of_phandle_args *dma_spec,
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spin_lock_irqsave(&dmamux->lock, flags);
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mux->chan_id = find_first_zero_bit(dmamux->dma_inuse,
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dmamux->dma_requests);
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set_bit(mux->chan_id, dmamux->dma_inuse);
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spin_unlock_irqrestore(&dmamux->lock, flags);
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if (mux->chan_id == dmamux->dma_requests) {
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spin_unlock_irqrestore(&dmamux->lock, flags);
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dev_err(&pdev->dev, "Run out of free DMA requests\n");
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ret = -ENOMEM;
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goto error;
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goto error_chan_id;
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}
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set_bit(mux->chan_id, dmamux->dma_inuse);
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spin_unlock_irqrestore(&dmamux->lock, flags);
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/* Look for DMA Master */
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for (i = 1, min = 0, max = dmamux->dma_reqs[i];
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@ -173,6 +174,8 @@ static void *stm32_dmamux_route_allocate(struct of_phandle_args *dma_spec,
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error:
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clear_bit(mux->chan_id, dmamux->dma_inuse);
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error_chan_id:
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kfree(mux);
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return ERR_PTR(ret);
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}
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