Merge tag 'random-5.18-rc2-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/crng/random

Pull random number generator fixes from Jason Donenfeld:

 - Another fixup to the fast_init/crng_init split, this time in how much
   entropy is being credited, from Jan Varho.

 - As discussed, we now opportunistically call try_to_generate_entropy()
   in /dev/urandom reads, as a replacement for the reverted commit. I
   opted to not do the more invasive wait_for_random_bytes() change at
   least for now, preferring to do something smaller and more obvious
   for the time being, but maybe that can be revisited as things evolve
   later.

 - Userspace can use FUSE or userfaultfd or simply move a process to
   idle priority in order to make a read from the random device never
   complete, which breaks forward secrecy, fixed by overwriting
   sensitive bytes early on in the function.

 - Jann Horn noticed that /dev/urandom reads were only checking for
   pending signals if need_resched() was true, a bug going back to the
   genesis commit, now fixed by always checking for signal_pending() and
   calling cond_resched(). This explains various noticeable signal
   delivery delays I've seen in programs over the years that do long
   reads from /dev/urandom.

 - In order to be more like other devices (e.g. /dev/zero) and to
   mitigate the impact of fixing the above bug, which has been around
   forever (users have never really needed to check the return value of
   read() for medium-sized reads and so perhaps many didn't), we now
   move signal checking to the bottom part of the loop, and do so every
   PAGE_SIZE-bytes.

* tag 'random-5.18-rc2-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/crng/random:
  random: check for signals every PAGE_SIZE chunk of /dev/[u]random
  random: check for signal_pending() outside of need_resched() check
  random: do not allow user to keep crng key around on stack
  random: opportunistically initialize on /dev/urandom reads
  random: do not split fast init input in add_hwgenerator_randomness()

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