Messages in this thread | | | From | David Laight <> | Subject | RE: [PATCH] Fix xoring of arch_get_random_long into crng->state array | Date | Wed, 29 May 2019 13:51:24 +0000 |
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From: Neil Horman > Sent: 29 May 2019 14:42 > On Tue, Apr 02, 2019 at 06:00:25PM -0400, Neil Horman wrote: > > When _crng_extract is called, any arch that has a registered > > arch_get_random_long method, attempts to mix an unsigned long value into > > the crng->state buffer, it only mixes in 32 of the 64 bits available, > > because the state buffer is an array of u32 values, even though 2 u32 > > are expected to be filled (owing to the fact that it expects indexes 14 > > and 15 to be filled). > > > > Bring the expected behavior into alignment by casting index 14 to an > > unsignled long pointer, and xoring that in instead. ... > > diff --git a/drivers/char/random.c b/drivers/char/random.c > > index 38c6d1af6d1c..8178618458ac 100644 > > --- a/drivers/char/random.c > > +++ b/drivers/char/random.c > > @@ -975,14 +975,16 @@ static void _extract_crng(struct crng_state *crng, > > __u8 out[CHACHA_BLOCK_SIZE]) > > { > > unsigned long v, flags; > > - > > + unsigned long *archrnd; > > if (crng_ready() && > > (time_after(crng_global_init_time, crng->init_time) || > > time_after(jiffies, crng->init_time + CRNG_RESEED_INTERVAL))) > > crng_reseed(crng, crng == &primary_crng ? &input_pool : NULL); > > spin_lock_irqsave(&crng->lock, flags); > > - if (arch_get_random_long(&v)) > > - crng->state[14] ^= v; > > + if (arch_get_random_long(&v)) { > > + archrnd = (unsigned long *)&crng->state[14]; > > + *archrnd ^= v; > > + }
Isn't that likely to generate a misaligned memory access?
David
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