Author: markm
Date: Mon Oct 5 07:41:12 2015
New Revision: 288703
URL: https://svnweb.freebsd.org/changeset/base/288703
Log:
It appears that under some circumstances, like virtualisiation, the
'rdrand' instruction may occasionally not return random numbers, in
spite of looping attempts to do so. The reusult is a KASSERT/panic.
Reluctantly accept this state-of-affairs, but make a noise about it.
if this 'noise' spams the console, it may be time to discontinue
using that source.
This is written in a general way to account for /any/ source that
might not supply random numbers when required.
Submitted by: jkh (report and slightly different fix)
Approved by: so (/dev/random blanket)
Modified:
head/sys/dev/random/random_harvestq.c
Modified: head/sys/dev/random/random_harvestq.c
==============================================================================
--- head/sys/dev/random/random_harvestq.c Mon Oct 5 07:40:18 2015
(r288702)
+++ head/sys/dev/random/random_harvestq.c Mon Oct 5 07:41:12 2015
(r288703)
@@ -211,7 +211,16 @@ random_sources_feed(void)
LIST_FOREACH(rrs, &source_list, rrs_entries) {
for (i = 0; i <
p_random_alg_context->ra_poolcount*(local_read_rate + 1); i++) {
n = rrs->rrs_source->rs_read(entropy, sizeof(entropy));
- KASSERT((n > 0 && n <= sizeof(entropy)), ("very bad
return from rs_read (= %d) in %s", n, __func__));
+ KASSERT((n <= sizeof(entropy)), ("%s: rs_read returned
too much data (%d > %d) in %s", __func__, n, sizeof(entropy)));
+ /* It would appear that in some circumstances (e.g.
virtualisation),
+ * the underlying hardware entropy source might not
always return
+ * random numbers. Accept this but make a noise. If too
much happens,
+ * can that source be trusted?
+ */
+ if (n == 0) {
+ printf("%s: rs_read for hardware device '%s'
returned no entropy.\n", __func__, rrs->rrs_source->rs_ident);
+ continue;
+ }
random_harvest_direct(entropy, n, (n*8)/2,
rrs->rrs_source->rs_source);
}
}
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