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3638bd90df
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()
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.