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Date: Thu, 18 Sep 2014 12:18:24 +0930 From: Rusty Russell <rusty@...tcorp.com.au> To: Amos Kong <akong@...hat.com>, virtualization@...ts.linux-foundation.org, kvm@...r.kernel.org, herbert@...dor.apana.org.au, m@...s.ch, mb@...sch.de, mpm@...enic.com, amit.shah@...hat.com, linux-kernel@...r.kernel.org Cc: Rusty Russell <rusty@...tcorp.com.au> Subject: [PATCH 3/5] hw_random: fix unregister race. The previous patch added one potential problem: we can still be reading from a hwrng when it's unregistered. Add a wait for zero in the hwrng_unregister path. Signed-off-by: Rusty Russell <rusty@...tcorp.com.au> --- drivers/char/hw_random/core.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c index dc9092a1075d..b4a21e9521cf 100644 --- a/drivers/char/hw_random/core.c +++ b/drivers/char/hw_random/core.c @@ -60,6 +60,7 @@ static DEFINE_MUTEX(rng_mutex); static DEFINE_MUTEX(reading_mutex); static int data_avail; static u8 *rng_buffer, *rng_fillbuf; +static DECLARE_WAIT_QUEUE_HEAD(rng_done); static unsigned short current_quality; static unsigned short default_quality; /* = 0; default to "off" */ @@ -98,6 +99,7 @@ static inline void cleanup_rng(struct kref *kref) if (rng->cleanup) rng->cleanup(rng); + wake_up_all(&rng_done); } static void set_current_rng(struct hwrng *rng) @@ -529,6 +531,9 @@ void hwrng_unregister(struct hwrng *rng) } mutex_unlock(&rng_mutex); + + /* Just in case rng is reading right now, wait. */ + wait_event(rng_done, atomic_read(&rng->ref.refcount) == 0); } EXPORT_SYMBOL_GPL(hwrng_unregister); -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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