l2tp: fix reading optional fields of L2TPv3
Use pskb_may_pull() to make sure the optional fields are in skb linear parts, so we can safely read them later. It's easy to reproduce the issue with a net driver that supports paged skb data. Just create a L2TPv3 over IP tunnel and then generates some network traffic. Once reproduced, rx err in /sys/kernel/debug/l2tp/tunnels will increase. Changes in v4: 1. s/l2tp_v3_pull_opt/l2tp_v3_ensure_opt_in_linear/ 2. s/tunnel->version != L2TP_HDR_VER_2/tunnel->version == L2TP_HDR_VER_3/ 3. Add 'Fixes' in commit messages. Changes in v3: 1. To keep consistency, move the code out of l2tp_recv_common. 2. Use "net" instead of "net-next", since this is a bug fix. Changes in v2: 1. Only fix L2TPv3 to make code simple. To fix both L2TPv3 and L2TPv2, we'd better refactor l2tp_recv_common. It's complicated to do so. 2. Reloading pointers after pskb_may_pull Fixes: f7faffa3 ("l2tp: Add L2TPv3 protocol support") Fixes: 0d76751f ("l2tp: Add L2TPv3 IP encapsulation (no UDP) support") Fixes: a32e0eec ("l2tp: introduce L2TPv3 IP encapsulation support for IPv6") Signed-off-by: NJacob Wen <jian.w.wen@oracle.com> Acked-by: NGuillaume Nault <gnault@redhat.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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