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Mon, 19 Oct 2026 01:50:13 -0700 (PDT) Date: Mon, 19 Oct 2026 04:50:10 -0400 From: "Michael S. Tsirkin" To: Pranjal Kumar Singh Cc: cve@kernel.org, netdev , Pablo Neira Ayuso , Jozsef Kadlecsik , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Willem de Bruijn , Paulos Yibelo , openvswitch , stable@vger.kernel.org, "fw@strlen.de" Subject: Re: Kernel bug report: unguarded deferred skb_checksum_help() writes corrupt the previously-validated IPv6 fixed header (IPv6 counterpart of commit 6785011f8b16, "ipv4: validate checksum_start before completing checksum") Message-ID: <20261019044815-mutt-send-email-mst@kernel.org> References: Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Mon, Oct 19, 2026 at 02:13:04PM +0530, Pranjal Kumar Singh wrote: > Hello Security Team, > > The IPv4 part of this was fixed some time ago in commit 6785011f8b16 > ("ipv4: validate checksum_start before completing checksum"): a packet > whose virtio_net_hdr csum metadata points its checksum start inside the > IP header makes skb_checksum_help() (the deferred csum completion) > rewrite the header the stack has already validated (fixed checksum > offset-width write at csum_start + csum_offset).  The IPv6 paths were > not covered, and they still are not: a 2-patch series mirroring that > commit for IPv4->IPv6, including its remaining not-yet-IPv6-guarded > sinks, is reproduced below and attached as patches/0001 and 0002. Thanks, I think this has been reported already. Just to clarify, the effect is just packet header corruption past validation, right? See [PATCH net-next v2 0/7] more virtio-net csum hardening for WIP fixes. -- MST