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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