CVE-2026-89940iio: buffer: Tie IIO dma fence lock lifetime to the fence

Official description

In the Linux kernel, the following vulnerability has been resolved: iio: buffer: Tie IIO dma fence lock lifetime to the fence The `iio_dma_fence` implementation currently uses a lock embedded in the `iio_dmabuf_priv`. But the `iio_dma_fence` can outlive the `iio_dmabuf_priv`, which can cause a use-after-free. Tie the lifetime of the lock to the lifetime of the fence by embedding them in the same struct. We can't just hold a reference to the `iio_dmabuf_priv` from the `iio_dma_fence` since `iio_buffer_dmabuf_release()` might sleep and the fence release callback is not allowed to sleep. Note that the `dma_fence` framework now has an internal lock that gets used when the passing `NULL` for `lock` in `dma_fence_init()`, but in order to allow this patch to be backportable use an external lock.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/6865d79fca17a80fbd60c12550ca9a5e0e20e0eb
• https://git.kernel.org/stable/c/510497e31be4f241103507315a859e2085ccb081
• https://git.kernel.org/stable/c/8b3e221590181a8beb3735bbabf166df02c839b5
• https://git.kernel.org/stable/c/f25ec4627d935dedfb5fe83bd2c2678cdcc19611