Currently, init_std_data calls ktime_get_real(). This imposes
awkward constraints on when init_std_data can be called, and
init_std_data is unlikely to collect the full unpredictable data
available to the timekeeping code, especially after resume.
Remove this code from random.c and add the appropriate
add_device_randomness calls to timekeeping.c instead.
Cc: John Stultz <john.stultz@xxxxxxxxxx>
Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
---
drivers/char/random.c | 2 --
kernel/time/timekeeping.c | 11 +++++++++++
2 files changed, 11 insertions(+), 2 deletions(-)
diff --git a/drivers/char/random.c b/drivers/char/random.c
index 7673e60..8dc3e3a 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -1263,12 +1263,10 @@ static void seed_entropy_store(void *ctx, u32 data)
static void init_std_data(struct entropy_store *r)
{
int i;
- ktime_t now = ktime_get_real();
unsigned long rv;
char log_prefix[128];
r->last_pulled = jiffies;
- mix_pool_bytes(r, &now, sizeof(now), NULL);
for (i = r->poolinfo->poolbytes; i > 0; i -= sizeof(rv)) {
rv = random_get_entropy();
mix_pool_bytes(r, &rv, sizeof(rv), NULL);
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 32d8d6a..9609db9 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -23,6 +23,7 @@
#include <linux/stop_machine.h>
#include <linux/pvclock_gtod.h>
#include <linux/compiler.h>
+#include <linux/random.h>
#include "tick-internal.h"
#include "ntp_internal.h"
@@ -835,6 +836,9 @@ void __init timekeeping_init(void)
memcpy(&shadow_timekeeper, &timekeeper, sizeof(timekeeper));
write_seqcount_end(&timekeeper_seq);
+
+ add_device_randomness(tk, sizeof(tk));
+
raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
}
@@ -976,6 +980,13 @@ static void timekeeping_resume(void)
timekeeping_suspended = 0;
timekeeping_update(tk, TK_MIRROR | TK_CLOCK_WAS_SET);
write_seqcount_end(&timekeeper_seq);
+
+ /*
+ * The timekeeping state has a decent chance of differing
+ * between resumptions of the same image.
+ */
+ add_device_randomness(tk, sizeof(tk));
+
raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
touch_softlockup_watchdog();
--
1.9.3
--
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