Description: loop: fix concurrent lo_open/lo_release
References:
Notes:
 bwh> Appears to have been introduced by commit f8933667953e "block: loop:
 bwh> don't hold lo_ctl_mutex in lo_open".
Bugs:
upstream: released (4.15-rc8) [ae6650163c66a7eff1acd6eb8b0f752dcfa8eba5]
4.9-upstream-stable: released (4.9.80) [56bc086358cac1a2949783646eabd57447b9d672]
3.16-upstream-stable: N/A "Vulnerability introduced later"
3.2-upstream-stable: N/A "Vulnerability introduced later"
sid: released (4.14.17-1)
4.9-stretch-security: released (4.9.80-1)
3.16-jessie-security: N/A "Vulnerability introduced later"
3.2-wheezy-security: N/A "Vulnerability introduced later"