[DCCP] Ackvec: fix soft lockup in ackvec handling code
[DCCP] Ackvec: fix soft lockup in ackvec handling code

A soft lockup existed in the handling of ack vector records.
Specifically, when a tail of the list of ack vector records was
removed, it was possible to end up iterating infinitely on an element
of the tail.

Signed-off-by: Andrea Bittau <4e0cab9a142dec191ae4bcc45cbdcb69fdef43f5@cs.ucl.ac.uk>
Signed-off-by: Ian McDonald <2a05ad6b77741e349ccfbdf734f819b9b1d576cb@jandi.co.nz>
Signed-off-by: David S. Miller <fe08d3c717adf2ae63592e4c9aec6e3e404d8e3e@davemloft.net>

TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs