[RogerNext]

拉取/合并请求描述：(PR description)

为什么提交这份PR (why to submit this PR)

The ls1c CAN receive path uses the raw 4-bit hardware DLC as the copy length. A malformed frame with DLC 9-15 therefore writes past the 8-byte classic CAN data buffer.

Fixes #11424.

你的解决方案是什么 (what is your solution)

Clamp the received DLC to the capacity of the hardware receive data array and use the clamped value when copying the payload. Valid classic CAN frames with DLC 0-8 are unchanged.

请提供验证的bsp和config (provide the config and bsp)

• BSP: bsp/loongson/ls1cdev
• .config: No configuration changes.
• action: Pending upstream PR CI. The local environment does not provide the mips-sde-elf cross compiler. A host boundary harness covering DLC 0-15 passed with -Wall -Wextra -Werror, and git diff --check passed.

当前拉取/合并请求的状态 Intent for your PR

必须选择一项 Choose one (Mandatory):

• 本拉取/合并请求是一个草稿版本 This PR is for a code-review and is intended to get feedback
• 本拉取/合并请求是一个成熟版本 This PR is mature, and ready to be integrated into the repo

代码质量 Code Quality：

我在这个拉取/合并请求中已经考虑了 As part of this pull request, I've considered the following:

• 已经仔细查看过代码改动的对比 Already check the difference between PR and old code
• 代码风格正确，包括缩进空格，命名及其他风格 Style guide is adhered to, including spacing, naming and other styles
• 没有垃圾代码，代码尽量精简，不包含#if 0代码，不包含已经被注释了的代码 All redundant code is removed and cleaned up
• 所有变更均有原因及合理的，并且不会影响到其他软件组件代码或BSP All modifications are justified and not affect other components or BSP
• 对难懂代码均提供对应的注释 I've commented appropriately where code is tricky
• 代码是高质量的 Code in this PR is of high quality
• 已经使用clang-format 源码格式化工具确保格式符合RT-Thread代码规范 This PR has been formatted with clang-format and complies with RT-Thread code specification
• 如果是新增bsp, 已经添加ci检查到.github/ALL_BSP_COMPILE.json 详细请参考链接BSP自查

[CLAassistant]

All committers have signed the CLA.

[github-actions]

👋 感谢您对 RT-Thread 的贡献！Thank you for your contribution to RT-Thread!

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如有问题欢迎联系我们，再次感谢您的贡献！💐
If you have any questions, feel free to reach out. Thanks again for your contribution!

[github-actions]

MemBrowse Memory Report

No memory changes detected for:

• loongson-ls1cdev