CVE-2022-49728

In the Linux kernel, the following vulnerability has been resolved:

ipv6: Fix signed integer overflow in _ip6append_data

Resurrect ubsan overflow checks and ubsan report this warning, fix it by change the variable [length] type to size_t.

UBSAN: signed-integer-overflow in net/ipv6/ip6output.c:1489:19 2147479552 + 8567 cannot be represented in type 'int' CPU: 0 PID: 253 Comm: err Not tainted 5.16.0+ #1 Hardware name: linux,dummy-virt (DT) Call trace: dumpbacktrace+0x214/0x230 showstack+0x30/0x78 dumpstacklvl+0xf8/0x118 dumpstack+0x18/0x30 ubsanepilogue+0x18/0x60 handleoverflow+0xd0/0xf0 ubsanhandleaddoverflow+0x34/0x44 _ip6appenddata.isra.48+0x1598/0x1688 ip6appenddata+0x128/0x260 udpv6sendmsg+0x680/0xdd0 inet6sendmsg+0x54/0x90 socksendmsg+0x70/0x88 _syssendmsg+0xe8/0x368 _syssendmsg+0x98/0xe0 _syssendmmsg+0xf4/0x3b8 _arm64syssendmmsg+0x34/0x48 invokesyscall+0x64/0x160 el0svccommon.constprop.4+0x124/0x300 doel0svc+0x44/0xc8 el0svc+0x3c/0x1e8 el0t64synchandler+0x88/0xb0 el0t64sync+0x16c/0x170

Changes since v1: -Change the variable [length] type to unsigned, as Eric Dumazet suggested. Changes since v2: -Don't change exthdrlen type in ip6makeskb, as Paolo Abeni suggested. Changes since v3: -Don't change ulen type in udpv6sendmsg and l2tpip6_sendmsg, as Jakub Kicinski suggested.