ip: validate header length on virtual device xmit
KMSAN detected read beyond end of buffer in vti and sit devices when passing truncated packets with PF_PACKET. The issue affects additional ip tunnel devices. Extend commit 76c0ddd8 ("ip6_tunnel: be careful when accessing the inner header") and commit ccfec9e5 ("ip_tunnel: be careful when accessing the inner header"). Move the check to a separate helper and call at the start of each ndo_start_xmit function in net/ipv4 and net/ipv6. Minor changes: - convert dev_kfree_skb to kfree_skb on error path, as dev_kfree_skb calls consume_skb which is not for error paths. - use pskb_network_may_pull even though that is pedantic here, as the same as pskb_may_pull for devices without llheaders. - do not cache ipv6 hdrs if used only once (unsafe across pskb_may_pull, was more relevant to earlier patch) Reported-by: Nsyzbot <syzkaller@googlegroups.com> Signed-off-by: NWillem de Bruijn <willemb@google.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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