fix: audio_free_buffers() add a NULL check.

[lichaofan2008]

On the Zhaoxin processor, there is a probabilistic occurrence of null pointer/double-free issues with audio_buffers[i].data, so a NULL check needs to be added.
在兆芯处理器上，audio_buffers[i].data 概率性出现空指针/重复释放的情况，所以需要增加 NULL 判断。

Bug: https://pms.uniontech.com/bug-view-345713.html

v20 BUG 分支合一到v25主线
Task: https://pms.uniontech.com/task-view-383481.html

Summary by Sourcery

Bug Fixes:

• Prevent null-pointer and double-free errors in audio_free_buffers() by skipping null entries and resetting freed buffer pointers to NULL.

[sourcery-ai]

Reviewer's guide (collapsed on small PRs)

Reviewer's Guide

Adds defensive NULL handling when freeing audio buffers to avoid double-free and null-pointer issues on specific processors.

State diagram for audio_buffers[i].data pointer lifecycle after fix

stateDiagram-v2
    [*] --> Uninitialized

    Uninitialized --> Allocated: buffer_allocated
    Allocated --> Freed: audio_free_buffers free
    Freed --> Null: audio_free_buffers set_to_NULL

    Allocated --> Null: explicit_set_NULL
    Null --> [*]

Loading

File-Level Changes

Change	Details	Files
Harden audio_free_buffers() against NULL and double-free issues for buffer data pointers.	Add a NULL check for each audio_buffers[i].data before calling free() Set audio_buffers[i].data to NULL immediately after freeing it to prevent subsequent double-free Document in-code (Chinese comment) that the check is required due to probabilistic NULL/double-free issues on Zhaoxin processors	libcam/libcam_audio/audio.c

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[deepin-ci-robot]

deepin pr auto review

这段代码修改主要是为了解决在特定硬件平台（兆芯处理器）上出现的内存管理问题。以下是对该 git diff 的详细审查意见，包括语法逻辑、代码质量、性能和安全性方面的分析：

1. 语法逻辑

• 审查结果：通过。
• 分析：
  • 引入了 if (audio_buffers[i].data == NULL) 判断，逻辑上是合理的。在 C 语言中，标准规定对 NULL 指针调用 free() 是安全的（不会产生副作用），但这段代码显然是为了应对更复杂的场景（如“重复释放”或“内存已被破坏导致指针异常”）。
  • 在 free 之后立即将指针置为 NULL (audio_buffers[i].data = NULL)，这是防止“悬垂指针”的标准做法，逻辑正确。

2. 代码质量

• 审查结果：良好，但有小幅提升空间。
• 分析：
  • 注释清晰：代码中明确添加了注释解释了修改原因（兆芯处理器上的概率性空指针/重复释放问题），这对于后续维护非常重要。
  • 防御性编程：增加了非空判断和置空操作，体现了防御性编程的思想，提高了代码的健壮性。
• 改进建议：
  • 考虑到 audio_buffers 本身也是一个指针，在循环结束后才 free(audio_buffers)。如果 audio_buffers 是全局变量或静态变量（看起来是静态的），且在 free(audio_buffers) 之后没有立即置为 NULL，那么如果其他地方有代码再次调用 audio_free_buffers，可能会导致 audio_buffers 变成悬垂指针，进而引发崩溃。
  • 建议：在函数末尾增加 audio_buffers = NULL;。

3. 代码性能

• 审查结果：影响极小，可忽略。
• 分析：
  • 增加了一次 if 判断和一次赋值操作。由于 AUDBUFF_NUM 通常是一个较小的常数（音频缓冲区数量），且此函数 audio_free_buffers 通常只在程序结束或关闭设备时调用（非热路径），因此性能损耗完全可以忽略不计。

4. 代码安全

• 审查结果：显著提升。
• 分析：
  • 防止重复释放：这是本次修改的核心。虽然在标准 C 库中 free(NULL) 是安全的，但如果指针指向的内存已经被释放且未被置空，再次调用 free 将导致 Double Free（双重释放）漏洞，可能引发程序崩溃或被攻击利用。将指针置为 NULL 彻底杜绝了这种情况。
  • 防止悬垂指针：释放后置空，防止了后续代码误用已释放的内存。
  • 应对硬件异常：注释提到兆芯处理器上概率性出现空指针，这可能是由于编译器优化、缓存一致性或硬件层面的内存对齐问题导致的。显式的 NULL 检查和置空增加了代码的确定性，有助于规避此类底层硬件兼容性问题。

总结与建议修改后的代码

这段修改是非常必要的，主要解决了内存安全和特定硬件兼容性问题。为了进一步提高代码质量，建议补充对 audio_buffers 自身的置空操作。

建议优化后的代码片段：

static void audio_free_buffers()
{
	int i;

	// 增加 audio_buffers 自身的非空判断，防止函数被重复调用时崩溃
	if (audio_buffers == NULL) {
		return;
	}

	for(i = 0; i < AUDBUFF_NUM; ++i)
	{
		// 在兆芯处理器上，audio_buffers[i].data 概率性出现空指针/重复释放的情况，所以这里需要增加判断
		if (audio_buffers[i].data != NULL) {
			free(audio_buffers[i].data);
			audio_buffers[i].data = NULL;
		}
	}

	free(audio_buffers);
	
	// 修复：释放主指针后立即置空，防止产生悬垂指针
	audio_buffers = NULL;
}

[sourcery-ai]

Hey - I've left some high level feedback:

• Instead of tying the comment to a specific processor, consider rephrasing it in generic terms (e.g., explaining that audio_free_buffers may be called multiple times and we guard against double free / NULL) so the rationale is clear and future-proof.
• If audio_free_buffers can be called concurrently, this change alone may not fully prevent double-free or race issues; you might want to confirm and, if needed, guard calls with appropriate synchronization rather than relying solely on a NULL check.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- Instead of tying the comment to a specific processor, consider rephrasing it in generic terms (e.g., explaining that audio_free_buffers may be called multiple times and we guard against double free / NULL) so the rationale is clear and future-proof.
- If audio_free_buffers can be called concurrently, this change alone may not fully prevent double-free or race issues; you might want to confirm and, if needed, guard calls with appropriate synchronization rather than relying solely on a NULL check.

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[deepin-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: lichaofan2008, lzwind

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[lichaofan2008]

/forcemerge

[deepin-bot]

This pr force merged! (status: unstable)