Commit d9e7972619334 "hwrng: add randomness to system from rng sources"
added a call to rng_get_data() from the hwrng_register() function.
However, some rng devices need initialization before data can be read
from them.
Also, the virtio-rng device does not behave properly when this call is
made in its probe() routine - the virtio core sets the DRIVER_OK status
bit only on a successful probe, which means the host ignores all
communication from the guest, and the guest insmod or boot process just
sits there doing nothing.
[ jac: Modify the API to allow drivers to disable reading at probe, new
patch, copied Amit's commit message. ]
CC: Kees Cook <keescook@xxxxxxxxxxxx>
CC: Jason Cooper <jason@xxxxxxxxxxxxxx>
CC: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
CC: <stable@xxxxxxxxxxxxxxx> # v3.15+
Signed-off-by: Amit Shah <amit.shah@xxxxxxxxxx>
Signed-off-by: Jason Cooper <jason@xxxxxxxxxxxxxx>
---
drivers/char/hw_random/core.c | 8 +++++---
include/linux/hw_random.h | 4 ++++
2 files changed, 9 insertions(+), 3 deletions(-)
diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
index 334601cc81cf..b7b6c48ca682 100644
--- a/drivers/char/hw_random/core.c
+++ b/drivers/char/hw_random/core.c
@@ -347,9 +347,11 @@ int hwrng_register(struct hwrng *rng)
INIT_LIST_HEAD(&rng->list);
list_add_tail(&rng->list, &rng_list);
- bytes_read = rng_get_data(rng, bytes, sizeof(bytes), 1);
- if (bytes_read > 0)
- add_device_randomness(bytes, bytes_read);
+ if (!(rng->flags & HWRNG_NO_READ_AT_PROBE)) {
+ bytes_read = rng_get_data(rng, bytes, sizeof(bytes), 1);
+ if (bytes_read > 0)
+ add_device_randomness(bytes, bytes_read);
+ }
out_unlock:
mutex_unlock(&rng_mutex);
out:
diff --git a/include/linux/hw_random.h b/include/linux/hw_random.h
index b4b0eef5fddf..5e358c7f3aae 100644
--- a/include/linux/hw_random.h
+++ b/include/linux/hw_random.h
@@ -15,6 +15,8 @@
#include <linux/types.h>
#include <linux/list.h>
+#define HWRNG_NO_READ_AT_PROBE BIT(0)
+
/**
* struct hwrng - Hardware Random Number Generator driver
* @name: Unique RNG name.
@@ -28,6 +30,7 @@
* Must not be NULL. *OBSOLETE*
* @read: New API. drivers can fill up to max bytes of data
* into the buffer. The buffer is aligned for any type.
+ * @flags: per-device properties
* @priv: Private data, for use by the RNG driver.
*/
struct hwrng {
@@ -37,6 +40,7 @@ struct hwrng {
int (*data_present)(struct hwrng *rng, int wait);
int (*data_read)(struct hwrng *rng, u32 *data);
int (*read)(struct hwrng *rng, void *data, size_t max, bool wait);
+ unsigned long flags;
unsigned long priv;
/* internal. */
--
2.0.0
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