On Fri, 29 Aug 2008 15:31:55 -0700

Aaron Straus  wrote:
> > -	if (r == &input_pool &&

quoted text
> > -	    r->entropy_count >= random_read_wakeup_thresh) {

> > +	if (r == &input_pool && entropy_count >= random_read_wakeup_thresh) {

> >  		wake_up_interruptible(&random_read_wait);

> >  		kill_fasync(&fasync, SIGIO, POLL_IN);

> >  	}

> > -

> > +	r->entropy_count = entropy_count;

>

> Here you set the entropy_count in the pool *after* waking up the reader.

> I was a little worried the reader would find the entropy_count unchanged

> and go back to sleep.

> 

Probably it doesn't matter because of the coverage of the lock but yes,

let's do the assignment first.
--- a/drivers/char/random.c~drivers-char-randomc-fix-a-race-which-can-lead-to-a-bogus-bug-fix-fix

+++ a/drivers/char/random.c

@@ -535,13 +535,13 @@ static void credit_entropy_bits(struct e

 		entropy_count = 0;

 	} else if (entropy_count > r->poolinfo->POOLBITS)

 		entropy_count = r->poolinfo->POOLBITS;

+	r->entropy_count = entropy_count;
 	/* should we wake readers? */

 	if (r == &input_pool && entropy_count >= random_read_wakeup_thresh) {

 		wake_up_interruptible(&random_read_wait);

 		kill_fasync(&fasync, SIGIO, POLL_IN);

 	}

-	r->entropy_count = entropy_count;

 	spin_unlock_irqrestore(&r->lock, flags);

 }
_
--

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