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authorJason A. Donenfeld <Jason@zx2c4.com>2022-09-20 16:12:00 +0200
committerJason A. Donenfeld <Jason@zx2c4.com>2022-09-23 12:27:57 +0200
commitd775335e350fc07e1322960ee291dc9079ab938e (patch)
tree9459588ff43af5215f615cf945fd2db7fbefe43a /drivers/char/random.c
parent745558f9588551b1fef9609d165e239bce30d3e8 (diff)
random: throttle hwrng writes if no entropy is credited
If a hwrng source does not provide an entropy estimate, it currently does not contribute at all to the CRNG. In order to help fix this, in case add_hwgenerator_randomness() is called with the entropy parameter set to zero, go to sleep until one reseed interval has passed. While the hwrng thread currently only runs under conditions where this is non-zero, this change is not harmful and prepares for future updates to the hwrng core. Cc: Herbert Xu <herbert@gondor.apana.org.au> Reviewed-by: Dominik Brodowski <linux@dominikbrodowski.net> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Diffstat (limited to 'drivers/char/random.c')
-rw-r--r--drivers/char/random.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/drivers/char/random.c b/drivers/char/random.c
index 16e0c5f6cf2f..520a385c7dab 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -865,9 +865,9 @@ void add_hwgenerator_randomness(const void *buf, size_t len, size_t entropy)
/*
* Throttle writing to once every reseed interval, unless we're not yet
- * initialized.
+ * initialized or no entropy is credited.
*/
- if (!kthread_should_stop() && crng_ready())
+ if (!kthread_should_stop() && (crng_ready() || !entropy))
schedule_timeout_interruptible(crng_reseed_interval());
}
EXPORT_SYMBOL_GPL(add_hwgenerator_randomness);