linux-kernel - [Bug] soft lockup in cleanup_mnt in Linux kernel v6.15-rc5

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Message-ID: <CAP=Rh=M3f8uNL0G=dwEALH2AQxV8tznsMjMdXJ9TWcgNhHooGg@mail.gmail.com>
Date: Wed, 21 May 2025 23:42:51 +0800
From: John <john.cs.hey@...il.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org
Subject: [Bug] soft lockup in cleanup_mnt in Linux kernel v6.15-rc5

Dear Linux Kernel Maintainers,

I hope this message finds you well.

I am writing to report a potential vulnerability I encountered during
testing of the Linux Kernel version v6.15-rc5.

Git Commit: 92a09c47464d040866cf2b4cd052bc60555185fb (tag: v6.15-rc5)

Bug Location: 0010:stack_depot_save_flags+0x133/0xa00 lib/stackdepot.c:619

Bug report: https://hastebin.com/share/jemayogixe.yaml

Complete log: https://hastebin.com/share/judumibuhe.perl

Entire kernel config: https://hastebin.com/share/padecilimo.ini

Root Cause Analysis:

A soft lockup was detected on CPU#0 during kernel execution, with the
testing process triggering the hang.
The issue occurred in the function stack_depot_save_flags() in
lib/stackdepot.c, which was invoked as part of the KASAN (Kernel
Address Sanitizer) infrastructure during a kfree() operation.
The failure originates from a pathological condition within
stack_depot_save_flags() where the kernel attempts to store a stack
trace associated with a memory deallocation event.
Specifically, the function enters a long-running or potentially
infinite loop while performing a linear search through the hash bucket
used for stack trace deduplication.

At present, I have not yet obtained a minimal reproducer for this
issue. However, I am actively working on reproducing it, and I will
promptly share any additional findings or a working reproducer as soon
as it becomes available.

Thank you very much for your time and attention to this matter. I
truly appreciate the efforts of the Linux kernel community.

Best regards,
John