After upgrading from sys-kernel/gentoo-sources-4.1.17 to 4.1.18 it stopped booting my system, rootfs is on LUKS device, I booted to old kernel and it was fine, also tried some debugging, testing old initramfs, testing/re-generating initramfs for old kernel (I think libgcrypt was recently updated), but still latest kernel fails.
Other people having same problem:
v3.10.97, v3.14.61 and 3.18.27 are also affected.
v3.12.54 works, too because it doesn't contain the broken patch in question.
Ran into this problem as well. As explained in the upstream bug report, it can be fixed by applying 2 patches:
Tested this on 4.1.18 and it solves the problem for me.
If you follow the recent mails the first proposed patch (which just the 2 patches) is incomplete. You could also argue that dropping the incomplete patches which were added in 4.1.18 and introduced the problems could be a better solution.
For 4.1, latest proposed patch set is https://mbroz.fedorapeople.org/tmp/4.1/
The following kernel(s) are fixed:
The following kernels are still affected:
However =sys-fs/cryptsetup-1.7.1 contains a workaround.
The following kernels are now fixed (fixed by revertion):
The following kernel is still affected:
=sys-kernel/gentoo-sources-3.18.31 finally contains the patch set.
Closing because all LTS kernels are now fixed or no longer affected.