linux-kernel - [Bug] "possible deadlock in rtnl

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Message-ID: <CAP=Rh=OEsn4y_2LvkO3UtDWurKcGPnZ_NPSXK=FbgygNXL37Sw@mail.gmail.com>
Date: Thu, 22 May 2025 08:52:57 +0800
From: John <john.cs.hey@...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] "possible deadlock in rtnl_newlink" 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: rtnl_newlink+0x86c/0x1dd0 net/core/rtnetlink.c:4011

Bug report: https://hastebin.com/share/ajavibofik.bash

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

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

Root Cause Analysis:
The deadlock warning is caused by a circular locking dependency
between two subsystems:

Path A (CPU 0):
Holds rtnl_mutex in rtnl_newlink() →
Then calls e1000_close() →
Triggers e1000_down_and_stop() →
Calls __cancel_work_sync() →
Tries to flush adapter->reset_task (→ needs work_completion lock)

Path B (CPU 1):
Holds work_completion lock while running e1000_reset_task() →
Then calls e1000_down() →
Which tries to acquire rtnl_mutex
These two execution paths result in a circular dependency:

CPU 0: rtnl_mutex → work_completion
CPU 1: work_completion → rtnl_mutex

This violates lock ordering and can lead to a deadlock under contention.
This bug represents a classic case of lock inversion between
networking core (rtnl_mutex) and a device driver (e1000 workqueue
reset`).
It is a design-level concurrency flaw that can lead to deadlocks under
stress or fuzzing workloads.

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