[ Upstream commit 87b3593bed1868b2d9fe096c01bcdf0ea86cbebf ] Ensure there is sufficient room to access the protocol field of the PPPoe header. Validate it once before the flowtable lookup, then use a helper function to access protocol field. Reported-by: syzbot+b6f07e1c07ef40199081@syzkaller.appspotmail.com Fixes: 72efd585f714 ("netfilter: flowtable: add pppoe support") Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org> Signed-off-by: Sasha Levin <sashal@kernel.org>