CVE-2026-89940

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.