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Sun, 08 Nov 2026 14:23:01 -0800 (PST) Received: from L9JK9NPFH9.lan ([104.28.20.58]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-c4d69f944a1sm91809566b.14.2026.11.08.14.22.59 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Sun, 08 Nov 2026 14:23:00 -0800 (PST) From: Tianyi Gao To: Jason Xing Cc: sashiko-bot@kernel.org, bpf@vger.kernel.org, netdev@vger.kernel.org, Magnus Karlsson , Maciej Fijalkowski , Stanislav Fomichev , kernel-team@cloudflare.com Subject: Re: [PATCH net-next 2/8] net: reserve extra TX headroom for local egress Date: Sun, 8 Nov 2026 22:22:56 +0000 Message-ID: <20261108222257.16997-1-tianyi@cloudflare.com> X-Mailer: git-send-email 2.56.0 In-Reply-To: References: <4b2f20b9a7bcca58fced690d20916efab55ad31a.1794020868.git.tianyi@cloudflare.com> 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=us-ascii Content-Transfer-Encoding: 8bit On Sun, Nov 08, 2026 at 03:35:12AM +0000, sashiko-bot@kernel.org wrote: > [Severity: High] > This problem wasn't introduced by this patch, but can hr + csum_start > overflow the u16 skb->csum_start field in xsk_skb_metadata() [1]? [ ... ] > When a UMEM is registered with chunk_size equal to PAGE_SIZE on a 64KB > page kernel (or with a large headroom reservation), desc->len can be up to > 65536 and hr + csum_start can exceed U16_MAX while still passing the > desc->len check. Truncating the sum into skb->csum_start wraps it below > skb_headroom(skb), making skb_checksum_start_offset() negative and > triggering skb_dump() and WARN_ONCE() in skb_checksum_help() or passing a > malformed skb to the driver in validate_xmit_skb(). This is a pre-existing issue, not introduced by this series. Jason already planned to fix it [2][3], but it has been five months. Jason, are you still planning to send the fix? If not, I can send it to net. [2] https://lore.kernel.org/all/CAL+tcoCp19F2rNxYL_LoGsY5MuBZ6cGKSZsj6D7kvQZcYp0wJg@mail.gmail.com/ [3] https://lore.kernel.org/all/CAL+tcoCgXG5MdPVzXavwMwk=jmPXgcB5aKpLK+TNXMVrsGmS9w@mail.gmail.com/