Messages in this thread Patch in this message | | | Date | Fri, 29 Aug 2008 15:42:15 -0700 | From | Andrew Morton <> | Subject | Re: drivers/char/random.c line 728 BUG |
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On Fri, 29 Aug 2008 15:31:55 -0700 Aaron Straus <aaron@merfinllc.com> wrote:
> > - if (r == &input_pool && > > - 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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