Date: Mon, 5 Oct 2015 07:41:13 +0000 (UTC) From: Mark Murray <markm@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r288703 - head/sys/dev/random Message-ID: <201510050741.t957fDXG084032@repo.freebsd.org>
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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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