lkml.org 
[lkml]   [2013]   [Nov]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 1/4] random: use device attach events for entropy
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@mit.edu>
> Cc: stable@vger.kernel.org
> ---
> 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


\
 
 \ /
  Last update: 2013-11-03 16:01    [W:0.107 / U:0.852 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site