CVE-2024-40970

In the Linux kernel, the following vulnerability has been resolved:

Avoid hw_desc array overrun in dw-axi-dmac

I have a use case where nr_buffers = 3 and in which each descriptor is composed by 3 segments, resulting in the DMA channel descs_allocated to be 9. Since axi_desc_put() handles the hw_desc considering the descs_allocated, this scenario would result in a kernel panic (hw_desc array will be overrun).

To fix this, the proposal is to add a new member to the axi_dma_desc structure, where we keep the number of allocated hw_descs (axi_desc_alloc()) and use it in axi_desc_put() to handle the hw_desc array correctly.

Additionally I propose to remove the axi_chan_start_first_queued() call after completing the transfer, since it was identified that unbalance can occur (started descriptors can be interrupted and transfer ignored due to DMA channel not being enabled).

Affected Software

References

• https://git.kernel.org/stable/c/333e11bf47fa8d477db90e2900b1ed3c9ae9b697
• https://git.kernel.org/stable/c/7c3bb96a20cd8db3b8824b2ff08b6cde4505c7e5
• https://git.kernel.org/stable/c/9004784e8d68bcd1ac1376407ba296fa28f04dbe
• https://git.kernel.org/stable/c/dd42570018f5962c10f215ad9c21274ed5d3541e
• https://git.kernel.org/stable/c/e151ae1ee065cf4b8ce4394ddb9d9c8df6370c66