CVE-2023-53094

/// Technical description

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

tty: serial: fsl_lpuart: fix race on RX DMA shutdown

From time to time DMA completion can come in the middle of DMA shutdown:

<process ctx>: <IRQ>:

lpuart32_shutdown()

lpuart_dma_shutdown()

del_timer_sync()

lpuart_dma_rx_complete()

lpuart_copy_rx_to_tty()

mod_timer()

lpuart_dma_rx_free()

When the timer fires a bit later, sport->dma_rx_desc is NULL:

Unable to handle kernel NULL pointer dereference at virtual address 0000000000000004

pc : lpuart_copy_rx_to_tty+0xcc/0x5bc

lr : lpuart_timer_func+0x1c/0x2c

Call trace:

lpuart_copy_rx_to_tty

lpuart_timer_func

call_timer_fn

__run_timers.part.0

run_timer_softirq

__do_softirq

__irq_exit_rcu

irq_exit

handle_domain_irq

gic_handle_irq

call_on_irq_stack

do_interrupt_handler

...

To fix this fold del_timer_sync() into lpuart_dma_rx_free() after

dmaengine_terminate_sync() to make sure timer will not be re-started in

lpuart_copy_rx_to

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References