[PATCH v3 0/3] crypto: atmel-sha204a - multiple RNG fixes

Lothar Rubusch
2026-04-22T21:09:49Z

When testing the RNG functionality on the Atmel SHA204a hardware, I
found the following issues: rngtest reported failures and hexdump
reveiled only the first 8 bytes out of 32 provided actually entropy.

Having a closer look into it, I found a (small) memory leak, missing
to free work_data, miss-reading of the count field into the entropy
fields and parts of the 32 random bytes staying 0 due to reading the
slow i2c device.

The series proposes fixes and how fixed functionality can be/was
verified. Executing rngtest afterward showed a decent result, due
to the i2c bus a bit slow.

All setups require selecting the Atmel-sha204a as active RNG.
$ cat /sys/class/misc/hw_random/rng_available
3f104000.rng 1-0064 none

$ echo 1-0064 > /sys/class/misc/hw_random/rng_current

$ cat /sys/class/misc/hw_random/rng_current
1-0064

Testing RNG properties currently shows problematic results:
$ rngtest < /dev/hwrng
rngtest 2.6
Copyright (c) 2004 by Henrique de Moraes Holschuh
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

rngtest: starting FIPS tests...
rngtest: bits received from input: 1040032
rngtest: FIPS 140-2 successes: 0
rngtest: FIPS 140-2 failures: 52
rngtest: FIPS 140-2(2001-10-10) Monobit: 52
rngtest: FIPS 140-2(2001-10-10) Poker: 52
rngtest: FIPS 140-2(2001-10-10) Runs: 52
rngtest: FIPS 140-2(2001-10-10) Long run: 52
rngtest: FIPS 140-2(2001-10-10) Continuous run: 52
rngtest: input channel speed: (min=7.631; avg=7.804; max=7.827)Kibits/s
rngtest: FIPS tests speed: (min=32.273; avg=32.701; max=33.056)Mibits/s
rngtest: Program run time: 130177956 microseconds

Signed-off-by: Lothar Rubusch <l.rubusch@gmail.com>
---
v2 -> v3: Removal blank line, rebased
v1 -> v2: Removal of C++ style comment (I saw it too late, sry for that)
---
Lothar Rubusch (3):
crypto: atmel-sha204a - fix memory leak at non-blocking RNG work_data
crypto: atmel-sha204a - fix truncated 32-byte blocking read
crypto: atmel-sha204a - fix non-blocking read logic

drivers/crypto/atmel-sha204a.c | 60 ++++++++++++++++++++++------------
1 file changed, 39 insertions(+), 21 deletions(-)

base-commit: 3bfbf5f0a99c991769ec562721285df7ab69240b
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2.53.0