linux-kernel - [Bug] soft lockup in __sk_free in Linux kernel v6.13

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Message-ID: <CALm_T+3Fxe4tiKiV9RpWyOpchgb6588d4qvgHn6qmDE5aMwKjg@mail.gmail.com>
Date: Tue, 8 Jul 2025 15:58:06 +0800
From: Luka <luka.2016.cs@...il.com>
To: "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>
Cc: Simon Horman <horms@...nel.org>, netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [Bug] soft lockup in __sk_free in Linux kernel v6.13

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 v6.13.

Git Commit: ffd294d346d185b70e28b1a28abe367bbfe53c04 (tag: v6.13)

Bug Location: __sk_free+0x1a9/0x4b0 net/core/sock.c:2322

Bug report: https://pastebin.com/0T4EFSse

Entire kernel config: https://pastebin.com/LepsHYGb

Root Cause Analysis:

A soft lockup is triggered during socket deallocation due to prolonged
execution in __sk_free(), where the destruction of socket-related
resources under heavy task context and scheduler pressure leads to
excessive CPU time consumption without preemption, ultimately stalling
the CPU and activating the watchdog.

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,
Luka