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authorTheodore Ts'o <tytso@mit.edu>2012-07-02 15:52:16 +0400
committerTheodore Ts'o <tytso@mit.edu>2012-07-15 04:17:28 +0400
commit775f4b297b780601e61787b766f306ed3e1d23eb (patch)
treee97e21669f0719636ccac0219f617bad6a0e8b54 /kernel/irq
parent74feec5dd83d879368c1081aec5b6a1cb6dd7ce2 (diff)
downloadlinux-775f4b297b780601e61787b766f306ed3e1d23eb.tar.xz
random: make 'add_interrupt_randomness()' do something sane
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> Cc: stable@vger.kernel.org
Diffstat (limited to 'kernel/irq')
-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 bdb180325551..131ca176b497 100644
--- a/kernel/irq/handle.c
+++ b/kernel/irq/handle.c
@@ -133,7 +133,7 @@ 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;
@@ -161,7 +161,7 @@ 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:
@@ -172,8 +172,7 @@ 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);