CVE ID:	CVE-2023-52527
Description:	In the Linux kernel, the following vulnerability has been resolved: ipv4, ipv6: Fix handling of transhdrlen in __ip{,6}_append_data() Including the transhdrlen in length is a problem when the packet is partially filled (e.g. something like send(MSG_MORE) happened previously) when appending to an IPv4 or IPv6 packet as we don't want to repeat the transport header or account for it twice. This can happen under some circumstances, such as splicing into an L2TP socket. The symptom observed is a warning in __ip6_append_data(): WARNING: CPU: 1 PID: 5042 at net/ipv6/ip6_output.c:1800 __ip6_append_data.isra.0+0x1be8/0x47f0 net/ipv6/ip6_output.c:1800 that occurs when MSG_SPLICE_PAGES is used to append more data to an already partially occupied skbuff. The warning occurs when 'copy' is larger than the amount of data in the message iterator. This is because the requested length includes the transport header length when it shouldn't. This can be triggered by, for example: sfd = socket(AF_INET6, SOCK_DGRAM, IPPROTO_L2TP); bind(sfd, ...); // ::1 connect(sfd, ...); // ::1 port 7 send(sfd, buffer, 4100, MSG_MORE); sendfile(sfd, dfd, NULL, 1024); Fix this by only adding transhdrlen into the length if the write queue is empty in l2tp_ip6_sendmsg(), analogously to how UDP does things. l2tp_ip_sendmsg() looks like it won't suffer from this problem as it builds the UDP packet itself.
Test IDs:	None available
Cross References:	Common Vulnerability Exposure (CVE) ID: CVE-2023-52527 https://git.kernel.org/stable/c/1fc793d68d50dee4782ef2e808913d5dd880bcc6 https://git.kernel.org/stable/c/1fc793d68d50dee4782ef2e808913d5dd880bcc6 https://git.kernel.org/stable/c/559d697c5d072593d22b3e0bd8b8081108aeaf59 https://git.kernel.org/stable/c/559d697c5d072593d22b3e0bd8b8081108aeaf59 https://git.kernel.org/stable/c/7626b9fed53092aa2147978070e610ecb61af844 https://git.kernel.org/stable/c/7626b9fed53092aa2147978070e610ecb61af844 https://git.kernel.org/stable/c/96b2e1090397217839fcd6c9b6d8f5d439e705ed https://git.kernel.org/stable/c/96b2e1090397217839fcd6c9b6d8f5d439e705ed https://git.kernel.org/stable/c/9d4c75800f61e5d75c1659ba201b6c0c7ead3070 https://git.kernel.org/stable/c/9d4c75800f61e5d75c1659ba201b6c0c7ead3070 https://git.kernel.org/stable/c/cd1189956393bf850b2e275e37411855d3bd86bb https://git.kernel.org/stable/c/cd1189956393bf850b2e275e37411855d3bd86bb https://git.kernel.org/stable/c/f6a7182179c0ed788e3755ee2ed18c888ddcc33f https://git.kernel.org/stable/c/f6a7182179c0ed788e3755ee2ed18c888ddcc33f https://git.kernel.org/stable/c/fe80658c08e3001c80c5533cd41abfbb0e0e28fd https://git.kernel.org/stable/c/fe80658c08e3001c80c5533cd41abfbb0e0e28fd