Patch "timekeeping: contribute wall clock to rng on time change" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    timekeeping: contribute wall clock to rng on time change

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     timekeeping-contribute-wall-clock-to-rng-on-time-cha.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit cd57e246465d84fac3e0eb2b338b665c889a0319
Author: Jason A. Donenfeld <Jason@xxxxxxxxx>
Date:   Sun Jul 17 23:53:34 2022 +0200

    timekeeping: contribute wall clock to rng on time change
    
    [ Upstream commit b8ac29b40183a6038919768b5d189c9bd91ce9b4 ]
    
    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@xxxxxxxxxxxxxxx
    Reviewed-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
    Reviewed-by: Eric Biggers <ebiggers@xxxxxxxxxx>
    Signed-off-by: Jason A. Donenfeld <Jason@xxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 871c912860ed..d6a0ff68df41 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"
@@ -1326,8 +1327,10 @@ 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));
+	}
 
 	return ret;
 }
@@ -2413,6 +2416,7 @@ int do_adjtimex(struct __kernel_timex *txc)
 	ret = timekeeping_validate_timex(txc);
 	if (ret)
 		return ret;
+	add_device_randomness(txc, sizeof(*txc));
 
 	if (txc->modes & ADJ_SETOFFSET) {
 		struct timespec64 delta;
@@ -2430,6 +2434,7 @@ int do_adjtimex(struct __kernel_timex *txc)
 	audit_ntp_init(&ad);
 
 	ktime_get_real_ts64(&ts);
+	add_device_randomness(&ts, sizeof(ts));
 
 	raw_spin_lock_irqsave(&timekeeper_lock, flags);
 	write_seqcount_begin(&tk_core.seq);