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a=rsa-sha256; c=relaxed/relaxed; d=foxmail.com; s=s201512; t=1793350678; bh=ozF9/5H+ecB+0UlehZ2yh0Si0DSQDpCL5DtZtA/tSm4=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=ro3NaZnPQcvQFxALMVrHOJa0DVV5T0Ul5Bd4oF7Wc+QBeGibQZfQaxG2DwRHzwqYZ la6MAWO9i3LxEDaAbyJfsPYctkpbNSYfvmNoRFRxt04bB3PrAYQmHpwlCrVWEFj3p2 BLMey5WC9ZuuG8TmzVQdO4C+v6o9bh+t01e1wRT8= Received: from HAPYCAO-MC1.tencent.com ([61.151.228.147]) by newxmesmtplogicsvrsza73-0.qq.com (NewEsmtp) with SMTP id E76B24F3; Fri, 30 Oct 2026 16:57:54 +0800 X-QQ-mid: xmsmtpt1793350674tdb2v2rsf Message-ID: X-QQ-XMAILINFO: M0msBj/q2J/m8IWtBXjfMlJsKdykaDyR4hK6S95T3OWzPyYwUYijwqapkxDZtc sp3NatzKx24/AES82aaA3/vb7qvlwDY7J1OP4J8Y7q1r7WXZZx46csdLugek73MBDl7+FLHaL6Vm OXtyzAIwEf4KTvH+ALR1Wyd1uf3atABfnuLSHA+gxwUGUjXcX5wX+bgPuKhAtaiHWOCT8OXYQsWy aWpUCixuU5Kg5C7cmCJm+9hyVNyIidR5y3j+QmqL7gx/wtHC2Ph0JqnLkGYjnCCGxbe6rw0xM0yy cADImU6u4BSd9KDDeklLnlBdom/ob8mux/01h2OqV/hypNpwzDq1WyRIyOyS/nwh/Eay/C8Eqq+t TR4jAVwubN2aoIZV8x/Ab8FgcOp66McV0kvZKtCQcRfZ/KmRwPBV1hUMZak0e3SFKKzgrDCfSahs poBj666Y89fl7eBPB8uG3y0svx5T9fp17txefRQ5AlYT+K6aNSZJEgs4O8ZxL8womaOl7MLd4b6E tgRkABVm2ByskLEOCGnF9N+sK7FoC0Wd+tGq50ks4RjXugBPRpZjqzgws09IhUtBq0zNy3SDdYKs YBc+0oyu78MOgGnxgum3kKkH5a9IrFoDhTclAR7raBOP4SJBGBn4I5jq+G1pmZPNgtTcbpCh7L4d CCmmcujOr20xzSzsN1RCYfniQktgN8J9vy2ir9121yKU0riW4ZhLon7GoI5xs3yGCMa1y2ePEpZj BAZ2xdQiurDE4aREgvzSqxtcYp8AwsZ4XAO0c6CFvUJdyTrx5nsQXIo8v7zZ5GqktpJX+F8MokeX 5C6/OXYeaQETdb0gqLJixYogDVi/L5k0LMfuGqSyR8K9NK1LMGqSxnKsTmKCdREkDeP1x0YxoW3o 8yFFXVF8xi9an1nW/i1lKolQQQ5QXEAuPDtqPPkQWcowGS9DvY+RVuVYGWbiOpjcRksGwfRbek7E J7sW4i2oWbyOvSwWirkfNXsMJlG8grzSMiCvWD05fJRFxbqpcDhqjlI9Uoohy5n+YsHvdldNaecn vKDIthBRW9NryXNIS7OSCpYjF9AFf3AcQajf3faweeCGAb2QGYkslPj0GERgZERclYgX3+BbD/5O H3tlOIx03crLMUwR4ahSRVAgfIWrFbIIS0X1AhzBdjHDATbr026ZbP07643Q== X-QQ-XMRINFO: MPJ6Tf5t3I/ylTmHUqvI8+Wpn+Gzalws3A== From: bo cao To: netdev-bot+sinfo@kernel.org Cc: davem@davemloft.net, dsahern@kernel.org, edumazet@kernel.org, horms@kernel.org, idosch@nvidia.com, kuba@kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, pabeni@redhat.com, stable@vger.kernel.org Subject: Re: [PATCH net v3] ipv6: fix dead half of the MTU guard in __ip6_append_data() Date: Fri, 30 Oct 2026 16:57:54 +0800 X-OQ-MSGID: <20261030085754.83762-1-treebacker@foxmail.com> X-Mailer: git-send-email 2.39.5 (Apple Git-154) In-Reply-To: <179335042941.3327.2302494904520671268@kernel.org> References: <179335042941.3327.2302494904520671268@kernel.org> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The issue was found during an LLM-assisted source audit of the IPv6 fragmentation path (manual code inspection with an LLM's help, not a production hit or a syzbot report). It was then verified at runtime with a standalone reproducer: a single sendmsg() on a raw IPv6 socket with a 1240-byte HOPOPTS cmsg and IPV6_MTU set to fragheaderlen + 1 triggers the skb_over_panic() described in the commit message (tested on 6.x, MSG_MORE on a device without NETIF_F_SG). The xfrm transport-mode variant from the v2 discussion was identified the same way, by inspection of the ip6_append_data_mtu() recompute path. bo cao