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authorJason A. Donenfeld <Jason@zx2c4.com>2022-07-17 23:53:34 +0200
committerJason A. Donenfeld <Jason@zx2c4.com>2022-07-18 15:04:04 +0200
commitb8ac29b40183a6038919768b5d189c9bd91ce9b4 (patch)
tree89cd406730b8343d5c1a470cf2933272d0a8d3ec
parent049f9ae93d033be6758ad865a9b89650f9f075ec (diff)
timekeeping: contribute wall clock to rng on time change
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 Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
-rw-r--r--kernel/time/timekeeping.c7
1 files changed, 6 insertions, 1 deletions
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 8e4b3c32fcf9..f72b9f1de178 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 @@ out:
/* 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;
}
@@ -2430,6 +2433,7 @@ 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;
@@ -2447,6 +2451,7 @@ 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);