# CVE-2025-39713: media: rainshadow-cec: fix TOCTOU race condition in rain\_interrupt()

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2025-09-05 · Updated: 2026-05-12

## Affected

- Linux: version range not reported
- Linux: 4.12

## Description

In the Linux kernel, the following vulnerability has been resolved: media: rainshadow-cec: fix TOCTOU race condition in rain_interrupt() In the interrupt handler rain_interrupt(), the buffer full check on rain->buf_len is performed before acquiring rain->buf_lock. This creates a Time-of-Check to Time-of-Use (TOCTOU) race condition, as rain->buf_len is concurrently accessed and modified in the work handler rain_irq_work_handler() under the same lock. Multiple interrupt invocations can race, with each reading buf_len before it becomes full and then proceeding. This can lead to both interrupts attempting to write to the buffer, incrementing buf_len beyond its capacity (DATA_SIZE) and causing a buffer overflow. Fix this bug by moving the spin_lock() to before the buffer full check. This ensures that the check and the subsequent buffer modification are performed atomically, preventing the race condition. An corresponding spin_unlock() is added to the overflow path to correctly release the lock. This possible bug was found by an experimental static analysis tool developed by our team.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory per the references below.
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## 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/2964dbe631fd21ad7873b1752b895548d3c12496
- https://git.kernel.org/stable/c/6aaef1a75985865d8c6c5b65fb54152060faba48
- https://git.kernel.org/stable/c/fbc81e78d75bf28972bc22b1599559557b1a1b83
- https://git.kernel.org/stable/c/3c3e33b7edca7a2d6a96801f287f9faeb684d655
- https://git.kernel.org/stable/c/1c2769dc80255824542ea5a4ff1a07dcdeb1603f
- https://git.kernel.org/stable/c/ed905fe7cba03cf22ae0b84cf1b73cd1c070423a
- https://git.kernel.org/stable/c/ff9dd3db6cd4c6b54a2ecbc58151bea4ec63bc59
- https://git.kernel.org/stable/c/7af160aea26c7dc9e6734d19306128cce156ec40

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