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authorTheodore Ts'o <tytso@mit.edu>2012-07-02 07:52:16 -0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2012-08-15 12:04:12 -0700
commitaa88dea2270f685349ab7b92169600452fe73b62 (patch)
treeb37b8609441ecb28a12e369795aea4e70bc6794c /kernel/irq/handle.c
parentf5a1367c1bc150e70e8db9bb6f2892e8e31648c7 (diff)
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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>
Diffstat (limited to 'kernel/irq/handle.c')
-rw-r--r--kernel/irq/handle.c7
1 files changed, 3 insertions, 4 deletions
diff --git a/kernel/irq/handle.c b/kernel/irq/handle.c
index 470d08c..10e0772 100644
--- a/kernel/irq/handle.c
+++ b/kernel/irq/handle.c
@@ -117,7 +117,7 @@ irqreturn_t
handle_irq_event_percpu(struct irq_desc *desc, struct irqaction *action)
{
irqreturn_t retval = IRQ_NONE;
- unsigned int random = 0, irq = desc->irq_data.irq;
+ unsigned int flags = 0, irq = desc->irq_data.irq;
do {
irqreturn_t res;
@@ -145,7 +145,7 @@ handle_irq_event_percpu(struct irq_desc *desc, struct irqaction *action)
/* Fall through to add to randomness */
case IRQ_HANDLED:
- random |= action->flags;
+ flags |= action->flags;
break;
default:
@@ -156,8 +156,7 @@ handle_irq_event_percpu(struct irq_desc *desc, struct irqaction *action)
action = action->next;
} while (action);
- if (random & IRQF_SAMPLE_RANDOM)
- add_interrupt_randomness(irq);
+ add_interrupt_randomness(irq, flags);
if (!noirqdebug)
note_interrupt(irq, desc, retval);