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Filename Latest commit message Latest commit date
Jason A. Donenfeld a1a2bae5ef random: simplify entropy debiting
commit 9c07f57869e90140080cfc282cc628d123e27704 upstream.

Our pool is 256 bits, and we only ever use all of it or don't use it at
all, which is decided by whether or not it has at least 128 bits in it.
So we can drastically simplify the accounting and cmpxchg loop to do
exactly this.  While we're at it, we move the minimum bit size into a
constant so it can be shared between the two places where it matters.

The reason we want any of this is for the case in which an attacker has
compromised the current state, and then bruteforces small amounts of
entropy added to it. By demanding a particular minimum amount of entropy
be present before reseeding, we make that bruteforcing difficult.

Note that this rationale no longer includes anything about /dev/random
blocking at the right moment, since /dev/random no longer blocks (except
for at ~boot), but rather uses the crng. In a former life, /dev/random
was different and therefore required a more nuanced account(), but this
is no longer.

Behaviorally, nothing changes here. This is just a simplification of
the code.

Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Dominik Brodowski <linux@dominikbrodowski.net>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2022-06-22 14:11:08 +02:00
arch random: remove unused irq_flags argument from add_interrupt_randomness() 2022-06-22 14:11:06 +02:00
block block: fix bio_clone_blkg_association() to associate with proper blkcg_gq 2022-06-14 18:11:50 +02:00
certs
crypto crypto: cryptd - Protect per-CPU resource by disabling BH. 2022-06-14 18:11:41 +02:00
Documentation x86/speculation/mmio: Add sysfs reporting for Processor MMIO Stale Data 2022-06-16 13:23:32 +02:00
drivers random: simplify entropy debiting 2022-06-22 14:11:08 +02:00
fs compat_ioctl: remove /dev/random commands 2022-06-22 14:11:03 +02:00
include random: simplify entropy debiting 2022-06-22 14:11:08 +02:00
init Kconfig: add config option for asm goto w/ outputs 2022-06-14 18:11:50 +02:00
ipc ipc/mqueue: use get_tree_nodev() in mqueue_get_tree() 2022-06-14 18:11:41 +02:00
kernel random: remove unused irq_flags argument from add_interrupt_randomness() 2022-06-22 14:11:06 +02:00
lib lib/crypto: sha1: re-roll loops to reduce code size 2022-06-22 14:11:03 +02:00
LICENSES
mm hugetlb: fix huge_pmd_unshare address update 2022-06-14 18:11:48 +02:00
net tcp: fix tcp_mtup_probe_success vs wrong snd_cwnd 2022-06-14 18:12:03 +02:00
samples
scripts scripts/gdb: change kernel config dumping method 2022-06-14 18:12:02 +02:00
security efi: Do not import certificates from UEFI Secure Boot for T2 Macs 2022-06-14 18:11:44 +02:00
sound ALSA: hda/conexant - Fix loopback issue with CX20632 2022-06-14 18:12:02 +02:00
tools netfilter: nat: really support inet nat without l3 address 2022-06-14 18:11:57 +02:00
usr
virt KVM: Prevent module exit until all VMs are freed 2022-04-15 14:18:27 +02:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS MAINTAINERS: co-maintain random.c 2022-06-22 14:11:05 +02:00
Makefile Linux 5.4.199 2022-06-16 13:23:32 +02:00
README

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.