@@ -8,6 +8,7 @@
#include <linux/clk.h>
#include <linux/crypto.h>
#include <linux/io.h>
+#include <linux/iopoll.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
@@ -43,16 +44,19 @@ static int qcom_rng_read(struct qcom_rng *rng, u8 *data, unsigned int max)
{
unsigned int currsize = 0;
u32 val;
+ int ret;
/* read random data from hardware */
do {
- val = readl_relaxed(rng->base + PRNG_STATUS);
- if (!(val & PRNG_STATUS_DATA_AVAIL))
- break;
+ ret = readl_poll_timeout(rng->base + PRNG_STATUS, val,
+ val & PRNG_STATUS_DATA_AVAIL,
+ 200, 10000);
+ if (ret)
+ return ret;
val = readl_relaxed(rng->base + PRNG_DATA_OUT);
if (!val)
- break;
+ return -EINVAL;
if ((max - currsize) >= WORD_SZ) {
memcpy(data, &val, WORD_SZ);
@@ -61,11 +65,10 @@ static int qcom_rng_read(struct qcom_rng *rng, u8 *data, unsigned int max)
} else {
/* copy only remaining bytes */
memcpy(data, &val, max - currsize);
- break;
}
} while (currsize < max);
- return currsize;
+ return 0;
}
static int qcom_rng_generate(struct crypto_rng *tfm,
@@ -87,7 +90,7 @@ static int qcom_rng_generate(struct crypto_rng *tfm,
mutex_unlock(&rng->lock);
clk_disable_unprepare(rng->clk);
- return 0;
+ return ret;
}
static int qcom_rng_seed(struct crypto_rng *tfm, const u8 *seed,
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: ceec5f5b5988 ("crypto: qcom-rng - Add Qcom prng driver") Cc: stable@vger.kernel.org # 4.19+ --- drivers/crypto/qcom-rng.c | 17 ++++++++++------- 1 file changed, 10 insertions(+), 7 deletions(-)