netdev - [Bug] soft lockup in ipv6_list

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Message-ID: <CALm_T+1s19Kr0=v94oUJEbN5ciGcumZDZp-hbn5=z_wPefqG1Q@mail.gmail.com>
Date: Tue, 8 Jul 2025 15:30:00 +0800
From: Luka <luka.2016.cs@...il.com>
To: "David S. Miller" <davem@...emloft.net>, David Ahern <dsahern@...nel.org>, 
	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 ipv6_list_rcv in Linux kernel v6.15

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.

Git Commit: 0ff41df1cb268fc69e703a08a57ee14ae967d0ca (tag: v6.15)

Bug Location: net/ipv6/ip6_input.c

Bug report: https://pastebin.com/vw0Vrd2m

Complete log: https://pastebin.com/HsUKHEpJ

Entire kernel config: https://pastebin.com/jQ30sdLk

Root Cause Analysis:

This bug is caused by a logic error in the ipv6_list_rcv() function
within the IPv6 input processing pipeline. During the handling of
multicast packets, specifically in the ip6_mc_input() and subsequent
calls, improper synchronization and premature release of socket
buffers (skb) through kfree_skb() lead to corrupted memory access.
This results in the triggering of a soft lockup condition where the
CPU becomes unresponsive due to prolonged execution in
skb_release_data() without yielding control. The issue is likely
rooted in incorrect reference management or double-free conditions on
shared skb structures under concurrent processing scenarios.

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