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Brian Masney ab9337c7cb crypto: qcom-rng - ensure buffer for generate is completely filled 
commit a680b1832c upstream.

The generate function in struct rng_alg expects that the destination
buffer is completely filled if the function returns 0. qcom_rng_read()
can run into a situation where the buffer is partially filled with
randomness and the remaining part of the buffer is zeroed since
qcom_rng_generate() doesn't check the return value. This issue can
be reproduced by running the following from libkcapi:

    kcapi-rng -b 9000000 > OUTFILE

The generated OUTFILE will have three huge sections that contain all
zeros, and this is caused by the code where the test
'val & PRNG_STATUS_DATA_AVAIL' fails.

Let's fix this issue by ensuring that qcom_rng_read() always returns
with a full buffer if the function returns success. Let's also have
qcom_rng_generate() return the correct value.

Here's some statistics from the ent project
(https://www.fourmilab.ch/random/) that shows information about the
quality of the generated numbers:

    $ ent -c qcom-random-before
    Value Char Occurrences Fraction
      0           606748   0.067416
      1            33104   0.003678
      2            33001   0.003667
    ...
    253   �        32883   0.003654
    254   �        33035   0.003671
    255   �        33239   0.003693

    Total:       9000000   1.000000

    Entropy = 7.811590 bits per byte.

    Optimum compression would reduce the size
    of this 9000000 byte file by 2 percent.

    Chi square distribution for 9000000 samples is 9329962.81, and
    randomly would exceed this value less than 0.01 percent of the
    times.

    Arithmetic mean value of data bytes is 119.3731 (127.5 = random).
    Monte Carlo value for Pi is 3.197293333 (error 1.77 percent).
    Serial correlation coefficient is 0.159130 (totally uncorrelated =
    0.0).

Without this patch, the results of the chi-square test is 0.01%, and
the numbers are certainly not random according to ent's project page.
The results improve with this patch:

    $ ent -c qcom-random-after
    Value Char Occurrences Fraction
      0            35432   0.003937
      1            35127   0.003903
      2            35424   0.003936
    ...
    253   �        35201   0.003911
    254   �        34835   0.003871
    255   �        35368   0.003930

    Total:       9000000   1.000000

    Entropy = 7.999979 bits per byte.

    Optimum compression would reduce the size
    of this 9000000 byte file by 0 percent.

    Chi square distribution for 9000000 samples is 258.77, and randomly
    would exceed this value 42.24 percent of the times.

    Arithmetic mean value of data bytes is 127.5006 (127.5 = random).
    Monte Carlo value for Pi is 3.141277333 (error 0.01 percent).
    Serial correlation coefficient is 0.000468 (totally uncorrelated =
    0.0).

This change was tested on a Nexus 5 phone (msm8974 SoC).

Signed-off-by: Brian Masney <bmasney@redhat.com>
Fixes: ceec5f5b59 ("crypto: qcom-rng - Add Qcom prng driver")
Cc: stable@vger.kernel.org # 4.19+
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Reviewed-by: Andrew Halaney <ahalaney@redhat.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
 		2022-03-23 09:16:40 +01:00
Documentation swiotlb: rework "fix info leak with DMA_FROM_DEVICE" 2022-03-16 14:23:43 +01:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
arch x86/module: Fix the paravirt vs alternative order 2022-03-19 13:47:51 +01:00
block block: drop unused includes in <linux/genhd.h> 2022-03-16 14:23:46 +01:00
certs certs: Add support for using elliptic curve keys for signing modules 2021-08-23 19:55:42 +03:00
crypto crypto: api - Move cryptomgr soft dependency into algapi 2022-02-11 09:10:26 +01:00
drivers crypto: qcom-rng - ensure buffer for generate is completely filled 2022-03-23 09:16:40 +01:00
fs btrfs: make send work with concurrent block group relocation 2022-03-16 14:23:46 +01:00
include xfrm: Check if_id in xfrm_migrate 2022-03-19 13:47:46 +01:00
init init: make unknown command line param message clearer 2021-11-18 19:17:11 +01:00
ipc ipc/sem: do not sleep with a spin lock held 2022-02-08 18:34:03 +01:00
kernel watch_queue: Make comment about setting ->defunct more accurate 2022-03-16 14:23:45 +01:00
lib ARM: 9178/1: fix unmet dependency on BITREVERSE for HAVE_ARCH_BITREVERSE 2022-03-19 13:47:48 +01:00
mm memfd: fix F_SEAL_WRITE after shmem huge page allocated 2022-03-08 19:12:48 +01:00
net tcp: make tcp_read_sock() more robust 2022-03-19 13:47:50 +01:00
samples samples: bpf: Fix 'unknown warning group' build warning on Clang 2022-01-27 11:03:29 +01:00
scripts kconfig: fix failing to generate auto.conf 2022-02-23 12:03:20 +01:00
security selinux: fix misuse of mutex_is_locked() 2022-03-02 11:47:48 +01:00
sound ASoC: cs4265: Fix the duplicated control name 2022-03-08 19:12:47 +01:00
tools kselftest/vm: fix tests build with old libc 2022-03-19 13:47:50 +01:00
usr usr/include/Makefile: add linux/nfc.h to the compile-test coverage 2022-02-01 17:27:15 +01:00
virt KVM: Fix lockdep false negative during host resume 2022-03-16 14:23:40 +01:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap mailmap: add Andrej Shadura 2021-10-18 20:22:03 -10:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Daniel Drake to credits 2021-09-21 08:34:58 +03:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS MAINTAINERS: adjust file entry for of_net.c after movement 2022-03-08 19:12:53 +01:00
Makefile Linux 5.15.30 2022-03-19 13:47:51 +01:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

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.