On Sun, Nov 03, 2013 at 08:33:12AM -0500, Theodore Ts'o wrote: > Some investigation from FreeBSD shows that there is entropy available > from measuring the device attach times: > > http://lists.randombit.net/pipermail/cryptography/2013-October/005689.html > > This will hopefully help us more quickly initialize the entropy pools > while the system is booting (which is one of the times when we really > badly need more entropy, especially in the case of the first boot > after an consumer electronics device is taken out of the box). > > Measurements indicate this makes a huge improvement in the security of > /dev/urandom during the boot sequence, so I'm cc'ing this to the > stable kernel series. Especially for embedded systems, which use > flash and which don't necessarily have the network enabled when they > first generate ssh or x.509 keys (sigh), this can be a big deal. > > Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx> > Cc: stable@xxxxxxxxxxxxxxx > --- > drivers/base/core.c | 3 +++ > drivers/char/random.c | 7 +++++++ > include/linux/random.h | 2 ++ > 3 files changed, 12 insertions(+) > > diff --git a/drivers/base/core.c b/drivers/base/core.c > index 8856d74..5e98fc3 100644 > --- a/drivers/base/core.c > +++ b/drivers/base/core.c > @@ -26,6 +26,7 @@ > #include <linux/async.h> > #include <linux/pm_runtime.h> > #include <linux/netdevice.h> > +#include <linux/random.h> > > #include "base.h" > #include "power/power.h" > @@ -1156,6 +1157,8 @@ int device_add(struct device *dev) > class_intf->add_dev(dev, class_intf); > mutex_unlock(&dev->class->p->mutex); > } > + add_device_attach_randomness(dev); > + > done: > put_device(dev); > return error; > diff --git a/drivers/char/random.c b/drivers/char/random.c > index f126bd2..51153fe 100644 > --- a/drivers/char/random.c > +++ b/drivers/char/random.c > @@ -829,6 +829,13 @@ void add_input_randomness(unsigned int type, unsigned int code, > } > EXPORT_SYMBOL_GPL(add_input_randomness); > > +void add_device_attach_randomness(struct device *dev) > +{ > + static struct timer_rand_state attach_state = { 0, }; > + > + add_timer_randomness(&attach_state, dev->devt); Is it an issue that dev->devt will almost always be 0,0 for this function call? Why not use the name instead here, that's more "unique" and every device has one, not just a tiny %. thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-crypto" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
