| Message ID | 20220623190014.1355583-1-Jason@zx2c4.com |
|---|---|
| State | New |
| Headers | show |
| Series | [v3] timekeeping: contribute wall clock to rng on time change | expand |
On Thu, Jun 23, 2022 at 9:10 PM Eric Biggers <ebiggers@kernel.org> wrote: > > 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)); This simple patch... I swear I know C, I promise... Thanks again, and sorry. Jason
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)); + } 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);
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(-)