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69efea712f
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Jason A. Donenfeld 69efea712f random: always use batched entropy for get_random_u{32,64} 
It turns out that RDRAND is pretty slow. Comparing these two
constructions:

  for (i = 0; i < CHACHA_BLOCK_SIZE; i += sizeof(ret))
    arch_get_random_long(&ret);

and

  long buf[CHACHA_BLOCK_SIZE / sizeof(long)];
  extract_crng((u8 *)buf);

it amortizes out to 352 cycles per long for the top one and 107 cycles
per long for the bottom one, on Coffee Lake Refresh, Intel Core i9-9880H.

And importantly, the top one has the drawback of not benefiting from the
real rng, whereas the bottom one has all the nice benefits of using our
own chacha rng. As get_random_u{32,64} gets used in more places (perhaps
beyond what it was originally intended for when it was introduced as
get_random_{int,long} back in the md5 monstrosity era), it seems like it
might be a good thing to strengthen its posture a tiny bit. Doing this
should only be stronger and not any weaker because that pool is already
initialized with a bunch of rdrand data (when available). This way, we
get the benefits of the hardware rng as well as our own rng.

Another benefit of this is that we no longer hit pitfalls of the recent
stream of AMD bugs in RDRAND. One often used code pattern for various
things is:

  do {
  	val = get_random_u32();
  } while (hash_table_contains_key(val));

That recent AMD bug rendered that pattern useless, whereas we're really
very certain that chacha20 output will give pretty distributed numbers,
no matter what.

So, this simplification seems better both from a security perspective
and from a performance perspective.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20200221201037.30231-1-Jason@zx2c4.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2020-02-27 23:21:52 -05:00
..
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acpi ACPI: PM: s2idle: Check fixed wakeup events in acpi_s2idle_wake() 2020-02-21 10:01:25 -08:00
amba
android for-5.6/io_uring-vfs-2020-01-29 2020-01-29 18:53:37 -08:00
ata libata-5.6-2020-02-05 2020-02-06 06:11:50 +00:00
atm Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next 2020-01-28 16:02:33 -08:00
auxdisplay
base ARM: SoC-related driver updates 2020-02-08 14:04:19 -08:00
bcma Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next 2020-01-28 16:02:33 -08:00
block Merge branch 'merge.nfs-fs_parse.1' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2020-02-08 13:26:41 -08:00
bluetooth Bluetooth: btrtl: Use kvmalloc for FW allocations 2020-01-24 19:57:53 +01:00
bus bus: moxtet: fix potential stack buffer overflow 2020-02-15 10:33:19 -08:00
cdrom
char random: always use batched entropy for get_random_u{32,64} 2020-02-27 23:21:52 -05:00
clk ARM: SoC: late updates 2020-02-08 14:17:27 -08:00
clocksource ARM: SoC: late updates 2020-02-08 14:17:27 -08:00
connector
counter
cpufreq Merge branch 'pm-cpufreq' 2020-02-14 10:40:48 +01:00
cpuidle ARM: SoC-related driver updates 2020-02-08 14:04:19 -08:00
crypto Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next 2020-01-28 16:02:33 -08:00
dax dax: Get rid of fs_dax_get_by_host() helper 2020-01-16 09:52:27 -08:00
dca
devfreq PM / devfreq: Add debugfs support with devfreq_summary file 2020-01-16 19:14:49 +09:00
dio
dma ARM: Device-tree updates 2020-02-08 13:58:44 -08:00
dma-buf
edac EDAC/sysfs: Remove csrow objects on errors 2020-02-13 13:29:41 +01:00
eisa
extcon
firewire
firmware ARM: SoC-related driver updates 2020-02-08 14:04:19 -08:00
fpga
fsi fsi: aspeed: add unspecified HAS_IOMEM dependency 2020-02-10 13:45:49 -08:00
gnss
gpio gpio: sifive: fix static checker warning 2020-02-10 13:54:17 +01:00
gpu Merge tag 'drm-intel-fixes-2020-02-20' of git://anongit.freedesktop.org/drm/drm-intel into drm-fixes 2020-02-21 12:46:54 +10:00
greybus
hid drm pull for 5.6-rc1 2020-01-30 08:04:01 -08:00
hsi
hv - Most of the commits here are work to enable host-initiated hibernation 2020-02-03 14:42:03 +00:00
hwmon hwmon: (w83627ehf) Fix crash seen with W83627DHG-P 2020-02-21 09:16:24 -08:00
hwspinlock hwspinlock: sirf: Use devm_hwspin_lock_register() to register hwlock controller 2020-01-21 16:16:36 -08:00
hwtracing
i2c Merge branch 'i2c/for-5.6' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux 2020-02-07 12:54:13 -08:00
i3c
ide proc: convert everything to "struct proc_ops" 2020-02-04 03:05:26 +00:00
idle intel_idle: Introduce 'states_off' module parameter 2020-02-03 11:57:18 +01:00
iio chrome platform changes for 5.6 2020-02-04 07:17:41 +00:00
infiniband SCSI fixes on 20200221 2020-02-22 11:00:52 -08:00
input Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input 2020-02-15 16:49:25 -08:00
interconnect
iommu iommu/arm-smmu: Restore naming of driver parameter prefix 2020-02-19 12:03:21 +01:00
ipack
irqchip irqchip/gic-v4.1: Avoid 64bit division for the sake of 32bit ARM 2020-02-09 15:47:37 -08:00
isdn proc: convert everything to "struct proc_ops" 2020-02-04 03:05:26 +00:00
leds leds: lm3532: add pointer to documentation and fix typo 2020-01-22 21:08:24 +01:00
lightnvm
macintosh powerpc updates for 5.6 2020-02-04 13:06:46 +00:00
mailbox
mcb
md block-5.6-2020-02-16 2020-02-16 12:35:52 -08:00
media chrome platform changes for 5.6 2020-02-04 07:17:41 +00:00
memory mvebu drivers for 5.6 (part 1) 2020-01-16 10:45:44 -08:00
memstick
message Merge ra.kernel.org:/pub/scm/linux/kernel/git/netdev/net 2020-01-19 22:10:04 +01:00
mfd chrome platform changes for 5.6 2020-02-04 07:17:41 +00:00
misc habanalabs: patched cb equals user cb in device memset 2020-02-11 11:12:47 +02:00
mmc ioremap changes for 5.6 2020-01-27 13:03:00 -08:00
mtd treewide: remove redundant IS_ERR() before error code check 2020-02-04 03:05:27 +00:00
mux
net bnxt_en: Issue PCIe FLR in kdump kernel to cleanup pending DMAs. 2020-02-20 16:05:42 -08:00
nfc nfc: pn544: Fix occasional HW initialization failure 2020-02-19 11:09:27 -08:00
ntb
nubus
nvdimm mm: Cleanup __put_devmap_managed_page() vs ->page_free() 2020-01-31 10:30:37 -08:00
nvme block-5.6-2020-02-22 2020-02-22 11:09:06 -08:00
nvmem Merge branch 'i2c/for-5.6' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux 2020-02-07 12:54:13 -08:00
of ARM: SoC-related driver updates 2020-02-08 14:04:19 -08:00
opp ioremap changes for 5.6 2020-01-27 13:03:00 -08:00
oprofile
parisc proc: convert everything to "struct proc_ops" 2020-02-04 03:05:26 +00:00
parport
pci pci-v5.6-fixes-1 2020-02-06 14:17:38 +00:00
pcmcia
perf perf/smmuv3: Use platform_get_irq_optional() for wired interrupt 2020-02-10 18:14:46 +00:00
phy treewide: remove redundant IS_ERR() before error code check 2020-02-04 03:05:27 +00:00
pinctrl pinctrl: fix pxa2xx.c build warnings 2020-02-04 03:05:24 +00:00
platform Merge branch 'akpm' (patches from Andrew) 2020-02-04 07:24:48 +00:00
pnp proc: convert everything to "struct proc_ops" 2020-02-04 03:05:26 +00:00
power ARM: SoC platform updates 2020-02-08 13:55:25 -08:00
powercap
pps
ps3
ptp Merge ra.kernel.org:/pub/scm/linux/kernel/git/netdev/net 2020-01-19 22:10:04 +01:00
pwm pwm: Remove set but not set variable 'pwm' 2020-01-20 15:40:49 +01:00
rapidio
ras
regulator - New Drivers 2020-02-03 14:51:57 +00:00
remoteproc remoteproc: qcom: q6v5-mss: Improve readability of reset_assert 2020-01-24 09:34:07 -08:00
reset
rpmsg rpmsg: add rpmsg support for mt8183 SCP. 2020-01-20 10:29:56 -08:00
rtc chrome platform changes for 5.6 2020-02-04 07:17:41 +00:00
s390 s390 updates for 5.6-rc3 2020-02-22 10:43:41 -08:00
sbus
scsi scsi: megaraid_sas: silence a warning 2020-02-12 19:13:48 -05:00
sfi
sh
siox
slimbus
soc soc/tegra: fuse: Fix build with Tegra194 configuration 2020-02-11 15:00:15 -08:00
soundwire soundwire: cadence: fix kernel-doc parameter descriptions 2020-01-16 17:34:38 +05:30
spi treewide: remove redundant IS_ERR() before error code check 2020-02-04 03:05:27 +00:00
spmi spmi: pmic-arb: Set lockdep class for hierarchical irq domains 2020-02-10 13:16:04 +01:00
ssb
staging staging: rtl8723bs: Remove unneeded goto statements 2020-02-10 10:32:38 -08:00
target scsi: Revert "target: iscsi: Wait for all commands to finish before freeing a session" 2020-02-14 17:13:54 -05:00
tc The main MIPS changes for 5.6: 2020-01-31 11:28:31 -08:00
tee ARM: SoC-related driver updates 2020-02-08 14:04:19 -08:00
thermal - Fix a SEVERE docs build failure for cpu idle cooling device (Randy Dunlap) 2020-01-31 14:39:21 -08:00
thunderbolt thunderbolt: Prevent crash if non-active NVMem file is read 2020-02-13 04:59:30 -08:00
tty vt: selection, close sel_buffer race 2020-02-13 12:10:07 -08:00
uio
usb USB: misc: iowarrior: add support for the 100 device 2020-02-17 10:44:43 +01:00
vfio VFIO updates for v5.6-rc1 2020-02-03 22:22:05 +00:00
vhost
video Kbuild updates for v5.6 (2nd) 2020-02-09 16:05:50 -08:00
virt
virtio virtio_balloon: Fix memory leaks on errors in virtballoon_probe() 2020-02-06 03:40:27 -05:00
visorbus
vlynq
vme Char/Misc driver changes for 5.6-rc1 2020-01-29 10:35:54 -08:00
w1 Char/Misc driver changes for 5.6-rc1 2020-01-29 10:35:54 -08:00
watchdog watchdog: da9062: Add dependency on I2C 2020-02-17 13:19:08 +01:00
xen xen: branch for v5.6-rc3 2020-02-21 16:10:10 -08:00
zorro Kbuild updates for v5.6 (2nd) 2020-02-09 16:05:50 -08:00
Kconfig
Makefile