random: make 'add_interrupt_randomness()' do something sane

commit 775f4b297b780601e61787b766f306ed3e1d23eb upstream.

We've been moving away from add_interrupt_randomness() for various
reasons: it's too expensive to do on every interrupt, and flooding the
CPU with interrupts could theoretically cause bogus floods of entropy
from a somewhat externally controllable source.

This solves both problems by limiting the actual randomness addition
to just once a second or after 64 interrupts, whicever comes first.
During that time, the interrupt cycle data is buffered up in a per-cpu
pool.  Also, we make sure the the nonblocking pool used by urandom is
initialized before we start feeding the normal input pool.  This
assures that /dev/urandom is returning unpredictable data as soon as
possible.

(Based on an original patch by Linus, but significantly modified by
tytso.)

Tested-by: Eric Wustrow <ewust@umich.edu>
Reported-by: Eric Wustrow <ewust@umich.edu>
Reported-by: Nadia Heninger <nadiah@cs.ucsd.edu>
Reported-by: Zakir Durumeric <zakir@umich.edu>
Reported-by: J. Alex Halderman <jhalderm@umich.edu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/include/linux/random.h b/include/linux/random.h
index 8f74538c96db..6ef39d7f2db1 100644
--- a/include/linux/random.h
+++ b/include/linux/random.h
@@ -52,7 +52,7 @@ extern void rand_initialize_irq(int irq);
 
 extern void add_input_randomness(unsigned int type, unsigned int code,
 				 unsigned int value);
-extern void add_interrupt_randomness(int irq);
+extern void add_interrupt_randomness(int irq, int irq_flags);
 
 extern void get_random_bytes(void *buf, int nbytes);
 void generate_random_uuid(unsigned char uuid_out[16]);