linux-kernel - Re: [PATCH v8 00/27] mm/ksw: Introduce KStackWatch debugging tool

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Message-ID: <aRIh4pBs7KCDhQOp@casper.infradead.org>
Date: Mon, 10 Nov 2025 17:33:22 +0000
From: Matthew Wilcox <willy@...radead.org>
To: Jinchao Wang <wangjinchao600@...il.com>
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Subject: Re: [PATCH v8 00/27] mm/ksw: Introduce KStackWatch debugging tool

On Tue, Nov 11, 2025 at 12:35:55AM +0800, Jinchao Wang wrote:
> Earlier this year, I debugged a stack corruption panic that revealed the
> limitations of existing debugging tools. The bug persisted for 739 days
> before being fixed (CVE-2025-22036), and my reproduction scenario
> differed from the CVE report—highlighting how unpredictably these bugs
> manifest.

Well, this demonstrates the dangers of keeping this problem siloed
within your own exfat group.  The fix made in 1bb7ff4204b6 is wrong!
It was fixed properly in 7375f22495e7 which lists its Fixes: as
Linux-2.6.12-rc2, but that's simply the beginning of git history.
It's actually been there since v2.4.6.4 where it's documented as simply:

      - some subtle fs/buffer.c race conditions (Andrew Morton, me)

As far as I can tell the changes made in 1bb7ff4204b6 should be
reverted.

> Initially, I enabled KASAN, but the bug did not reproduce. Reviewing the
> code in __blk_flush_plug(), I found it difficult to trace all logic
> paths due to indirect function calls through function pointers.

So why is the solution here not simply to fix KASAN instead of this
giant patch series?