Description: packet: fix races in fanout_add()
References:
Notes:
 bwh> The races can clearly lead to a UAF since 4.2.  The impact may be
 bwh> less severe in earlier versions but still needs to be fixed.
Bugs:
upstream: released (4.10) [d199fab63c11998a602205f7ee7ff7c05c97164b]
4.9-upstream-stable: released (4.9.13) [722737f27774b14be5a1d2d3b9281dcded7c48b2]
3.16-upstream-stable: released (3.16.42) [packet-fix-races-in-fanout_add.patch]
3.2-upstream-stable: released (3.2.87) [packet-fix-races-in-fanout_add.patch]
sid: released (4.9.13-1)
3.16-jessie-security: released (3.16.39-1+deb8u2) [bugfix/all/packet-fix-races-in-fanout_add.patch]
3.2-wheezy-security: released (3.2.86-1) [bugfix/all/packet-fix-races-in-fanout_add.patch]