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[222.167.244.67]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3ae5a944acasm192658a91.7.2026.10.27.15.51.58 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Tue, 27 Oct 2026 15:52:02 -0700 (PDT) From: Guoshuai Yang To: netdev-bot+sashiko@kernel.org Cc: Guoshuai Yang , Steffen Klassert , Herbert Xu , Sabrina Dubroca , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , David Ahern , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH net v3] xfrm: esp: reset outer TCP GSO metadata on espintcp input Date: Wed, 28 Oct 2026 06:51:55 +0800 Message-ID: <20261027225155.49607-1-yangguoshuai@gmail.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: <179308626642.3134.14988418944940808850@kernel.org> References: <20261023065311.65031-1-yangguoshuai@gmail.com> <179308626642.3134.14988418944940808850@kernel.org> X-Mailing-List: netdev@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On Tue, Oct 27, 2026 at 07:31:06AM +0000, netdev-bot+sashiko@kernel.org wrote: > [Severity: Low] > Is enabling rx-gro-list enough on its own to reach this case? ... > Could the commit message describe that topology? Could it also say that > this half of the fix depends on TCP fraglist GRO? That feature is much > newer than e27cca96cd68 from the Fixes: tag, so on stable trees without it > the pre-pass does nothing. > > [Severity: Medium] > Is there still a BUG_ON() at this point? In the tree this patch targets, > skb_segment() handles the condition like this: ... > Could the commit message say which kernel the trace came from? Could it > also describe the behavior on the kernels this patch targets? > > [Severity: Medium] > Can fragp point at the ->next field of a member that is still shared when > this store happens? ... > This relink pattern looks like it comes from ___pskb_trim(). That function > handles skb_shared() on every member before skipping any, so it never > writes through a shared predecessor. Would it be safer to privatize every > member walked so far, including the skipped ones, or to copy from the first > shared member onward the way skb_cow_data() does? Thank you for the detailed review. All three points are valid: 1. In esp_reset_espintcp_fraglist_gso(), skipping a shared predecessor before checking skb_shared(frag) means a subsequent *fragp = frag store would overwrite the shared predecessor's ->next pointer across both clones. Unsharing every walked frag_list member first (as ___pskb_trim() does) before checking SKB_GSO_FRAGLIST guarantees that fragp always points into an unshared predecessor. 2. In the commit message, I will clarify that the BUG_ON(!list_skb->head_frag) oops trace was captured on a 6.12 LTS kernel, whereas on current mainline kernels skb_segment() hits DEBUG_NET_WARN_ON_ONCE(1) and returns -EINVAL, causing validate_xmit_skb() to drop the packet. 3. I will also clarify the topology required for TCP fraglist GRO (SKB_GSO_FRAGLIST) to reach esp_input() (e.g., rx-gro-list on a device in an outer netns forwarded across veth into the netns hosting the espintcp socket) and note that this pre-pass applies to kernels with TCP fraglist GRO support. I will send a v4 with these updates. pw-bot: cr