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a=rsa-sha256; c=relaxed/relaxed; d=foxmail.com; s=s201512; t=1793585906; bh=LzpH6ZlFtWx3iq/V4Ca3j+tPjclLZq1yC4pTJfDWRc8=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=S6zdqfibLP8H6Zdr9umZyiK2q3aifHaVmVT+mJIwGHRyMZ1iwn8x6OiBXEUOw3Q0s FBF4FEs6/dP2rlHkxmArRQC1L8rDn7rcPl1qe9+b5V8H5GAlUIo7XPCEeSGPowGkiL cD14CqSnLHr6RgSyXe5wiJQwzyATBjQmczsDcG/0= Received: from HAPYCAO-MC1.tencent.com ([61.151.228.151]) by newxmesmtplogicsvrsza63-0.qq.com (NewEsmtp) with SMTP id 496A20BF; Mon, 02 Nov 2026 10:18:22 +0800 X-QQ-mid: xmsmtpt1793585902tmd4v4x7m Message-ID: X-QQ-XMAILINFO: NiqzJuKCE4mBRyz1QDXp2j/ZkT+xuxIe05NGxcYlTGV8GEezSHfKoryJkXsZJB 1llyNa6yFZVVAWVwGw2fcqVeLmCNexacwb9sjrqMnP1KNLc2zgrOakwYCyeU0NKEalvdlbVslc4A JQVh0rwZKlLhZ2D8ivvJ6iGPrQLLdGqREiDVaS//QGSItB0EY6IR+lrtvJ5Q98HWxEtBKmmGX6Uq M+bd/HUqom9qy+6Nqnu9xEQ73N+vIYg0gVIEp8ONZF6VOm/skfCLnMaxa11Y+2Mc5WGpCOrxp9M9 YUswaPHdYazWoLHqPd6cXZoOnVhuyW1o3puWAppADPw532wOt+QKtb+rVAb6s5H5lYabvq0hSpe8 jzRQfAeCkWmkGSSPkPGeGMJ4e6fWkSELkpzlJVA/S3TVkzGlsl2JnKW/biFAfmWtK1/qsxbU2w29 EsO3nDwVNeHNdCO8jGJjapLHkII/0fDa4U1hQq0dsg1n3zjHraJQgbWtvMo+ho681zTOSrFgDf+N GMDHMPr8Fksc+V0qg69mY/G2gjZpY2gAjJg+m4Uthzs681jKtUrCM6SyBQRwj22gqo3ND7mB/waj p00aTFP1v9lcFTDv8EXCVVvKX61jp/22RJjg9WB+QqutSo959MJD7C1R2L0kb31hGgAs0YZACt2l eNAGqHumSaVelopu/qC+DxQe2LORC7qgtzqywZ92cu3um258yLASOCGGqhwNsMjeH2UCobJSt19M CkrX8JsDMnozeYutGbrTc4Ja+c5lWTv+jrCDjcrq6ly2mfsSsOOcG3q81TqWkTh3AwO5gUNT1QCr 3xMH9loKXjkv3+z88I+4uFZk2F7Em7Rn7jtp0EWiJS90NEEPc5nBMaMmpXpyFaYhCeg7aO4O2inO N8f3TOSaMNcwZFITlFIhu2fKBFXqyYHr6/hbxcBn7k5Q9jvT4dyQsqUP5d4xPi9JmnVfrX6tbcCS qVXGc//tb+iFT7PeODR4/LyswXItgIkYnjfjlZqKanvbhkcagXa6V2PLaOvNbJFRRj9Qs7t43G66 CjnKe8OwAvJCWs4OMXMAIy2jNeSwjwkYh/nIN9+TPaiaDFKebLMWuIF1vWBLegcXQdpV6xVNTzkI dTkdXjTKso12NDPMB0gTLcPslB+Y3uWM7lbE32xr8GXRLs4VM5xN14dD1hAFGiJsJlQs4tUDRx8Y UkXu4lMyler4tHSn6EBUv3t0bObpYaT2K3sN0CCsyJ5RxxMgs9b2BDJeKiPFxmlZHYHU4= X-QQ-XMRINFO: MSVp+SPm3vtSI1QTLgDHQqIV1w2oNKDqfg== 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, treebacker@foxmail.com, willemdebruijn.kernel@gmail.com Subject: Re: [PATCH net v4] ipv6: fix dead half of the MTU guard in __ip6_append_data() Date: Mon, 2 Nov 2026 10:18:22 +0800 X-OQ-MSGID: <20261102021822.91796-1-treebacker@foxmail.com> X-Mailer: git-send-email 2.39.5 (Apple Git-154) In-Reply-To: <179358500215.3286.12801503551646664009@kernel.org> References: <179358500215.3286.12801503551646664009@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 Apologies -- this information was already provided in the v3 thread, and it was my oversight not to carry it into the v4 commit message as the bot had asked. It will be included in the commit message of any future revision. As replied on the v3 thread: 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