diff options
| author | Rusty Russell <rusty@rustcorp.com.au> | 2014-12-08 16:50:38 +0800 |
|---|---|---|
| committer | Herbert Xu <herbert@gondor.apana.org.au> | 2014-12-22 23:02:40 +1100 |
| commit | a027f30d72f2c4d27d6dd9bd053205d3102de7d1 (patch) | |
| tree | c430933226d1f44da1cb2aca7c418a9baea8e17b | |
| parent | 3a2c0ba5ad00c018c0bef39a2224aca950aa33f2 (diff) | |
hwrng: 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@rustcorp.com.au>
Signed-off-by: Amos Kong <akong@redhat.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
| -rw-r--r-- | drivers/char/hw_random/core.c | 12 | ||||
| -rw-r--r-- | include/linux/hw_random.h | 1 |
2 files changed, 13 insertions, 0 deletions
diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c index 089c18dc579e..8d609a026465 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 +99,11 @@ static inline void cleanup_rng(struct kref *kref) if (rng->cleanup) rng->cleanup(rng); + + /* cleanup_done should be updated after cleanup finishes */ + smp_wmb(); + rng->cleanup_done = true; + wake_up_all(&rng_done); } static void set_current_rng(struct hwrng *rng) @@ -494,6 +500,8 @@ int hwrng_register(struct hwrng *rng) add_early_randomness(rng); } + rng->cleanup_done = false; + out_unlock: mutex_unlock(&rng_mutex); out: @@ -525,6 +533,10 @@ void hwrng_unregister(struct hwrng *rng) kthread_stop(hwrng_fill); } else mutex_unlock(&rng_mutex); + + /* Just in case rng is reading right now, wait. */ + wait_event(rng_done, rng->cleanup_done && + atomic_read(&rng->ref.refcount) == 0); } EXPORT_SYMBOL_GPL(hwrng_unregister); diff --git a/include/linux/hw_random.h b/include/linux/hw_random.h index c212e71ea886..7832e5008959 100644 --- a/include/linux/hw_random.h +++ b/include/linux/hw_random.h @@ -46,6 +46,7 @@ struct hwrng { /* internal. */ struct list_head list; struct kref ref; + bool cleanup_done; }; /** Register a new Hardware Random Number Generator driver. */ |