diff mbox series

timekeeping: contribute wall clock to rng on time change

Message ID 20220623165226.1335679-1-Jason@zx2c4.com
State New
Headers show
Series timekeeping: contribute wall clock to rng on time change | expand

Commit Message

Jason A. Donenfeld June 23, 2022, 4:52 p.m. UTC
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 | 6 ++++++
 1 file changed, 6 insertions(+)
diff mbox series

Patch

diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 8e4b3c32fcf9..ad55da792f13 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -1346,6 +1346,9 @@  int do_settimeofday64(const struct timespec64 *ts)
 	if (!ret)
 		audit_tk_injoffset(ts_delta);
 
+	ktime_get_real_ts64(&xt);
+	add_device_randomness(&xt, sizeof(xt));
+
 	return ret;
 }
 EXPORT_SYMBOL(do_settimeofday64);
@@ -2475,6 +2478,9 @@  int do_adjtimex(struct __kernel_timex *txc)
 
 	ntp_notify_cmos_timer();
 
+	ktime_get_real_ts64(&ts);
+	add_device_randomness(&ts, sizeof(ts));
+
 	return ret;
 }