When collecting TCP flags we check that the IP header indicates that
a TCP header is present but not that the packet is actually long
enough to contain the header. This adds a check to prevent reading
off the end of the packet.
In practice, this is only likely to result in reading of bad data and
not a crash due to the presence of struct skb_shared_info at the end
of the packet.
Signed-off-by: Jesse Gross <jesse@nicira.com>
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