CVE-2022-48867

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

dmaengine: idxd: Prevent use after free on completion memory

On driver unload any pending descriptors are flushed at the time the interrupt is freed: idxd_dmaengine_drv_remove() -> drv_disable_wq() -> idxd_wq_free_irq() -> idxd_flush_pending_descs().

If there are any descriptors present that need to be flushed this flow triggers a not present page fault as below:

BUG: unable to handle page fault for address: ff391c97c70c9040 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page

The address that triggers the fault is the address of the descriptor that was freed moments earlier via: drv_disable_wq()->idxd_wq_free_resources()

Fix the use after free by freeing the descriptors after any possible usage. This is done after idxd_wq_reset() to ensure that the memory remains accessible during possible completion writes by the device.

Weakness

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory “belongs” to the code that operates on the new pointer.

Affected Software

Potential Mitigations

References

• https://git.kernel.org/stable/c/1beeec45f9ac31eba52478379f70a5fa9c2ad005
• https://git.kernel.org/stable/c/b9e8e3fcfec625fc1c2f68f684448aeeb882625b