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SubjectRe: [PATCH v3] timekeeping: contribute wall clock to rng on time change
On Thu, Jun 23, 2022 at 09:00:14PM +0200, Jason A. Donenfeld wrote:
> The rng's random_init() function contributes the real time to the rng at
> boot time, so that events can at least start in relation to something
> particular in the real world. But this clock might not yet be set that
> point in boot, so nothing is contributed. In addition, the relation
> between minor clock changes from, say, NTP, and the cycle counter is
> potentially useful entropic data.
>
> This commit addresses this by mixing in a time stamp on calls to
> settimeofday and adjtimex. No entropy is credited in doing so, so it
> doesn't make initialization faster, but it is still useful input to
> have.
>
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Cc: stable@vger.kernel.org
> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
> ---
> kernel/time/timekeeping.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
> index 8e4b3c32fcf9..49ee8ef16544 100644
> --- a/kernel/time/timekeeping.c
> +++ b/kernel/time/timekeeping.c
> @@ -23,6 +23,7 @@
> #include <linux/pvclock_gtod.h>
> #include <linux/compiler.h>
> #include <linux/audit.h>
> +#include <linux/random.h>
>
> #include "tick-internal.h"
> #include "ntp_internal.h"
> @@ -1343,8 +1344,10 @@ int do_settimeofday64(const struct timespec64 *ts)
> /* Signal hrtimers about time change */
> clock_was_set(CLOCK_SET_WALL);
>
> - if (!ret)
> + if (!ret) {
> audit_tk_injoffset(ts_delta);
> + add_device_randomness(&ts, sizeof(ts));
> + }

It should be:

add_device_randomness(ts, sizeof(*ts));

- Eric

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