git: 40f9f2279c0f - stable/13 - kern: random: drop read_rate and associated functionality

The branch stable/13 has been updated by kevans:

URL: https://cgit.FreeBSD.org/src/commit/?id=40f9f2279c0fd6f9e1829f786eea3d49e45c9f32

commit 40f9f2279c0fd6f9e1829f786eea3d49e45c9f32
Author:     Kyle Evans <kevans@FreeBSD.org>
AuthorDate: 2021-09-20 04:59:09 +0000
Commit:     Kyle Evans <kevans@FreeBSD.org>
CommitDate: 2021-10-06 06:41:18 +0000

    kern: random: drop read_rate and associated functionality
    
    Refer to discussion in PR 230808 for a less incomplete discussion, but
    the gist of this change is that we currently collect orders of magnitude
    more entropy than we need.
    
    The excess comes from bytes being read out of /dev/*random.  The default
    rate at which we collect entropy without the read_rate increase is
    already more than we need to recover from a compromise of an internal
    state.
    
    For stable/13, the read_rate_increment symbol remains as a stub to avoid
    breaking loadable random modules.
    
    (cherry picked from commit 6895cade9421238abf541f24fb9327ebd19e94ff)
---
 sys/dev/random/random_harvestq.c | 13 +++----------
 sys/dev/random/randomdev.c       |  2 --
 2 files changed, 3 insertions(+), 12 deletions(-)

diff --git a/sys/dev/random/random_harvestq.c b/sys/dev/random/random_harvestq.c
index 6838cf23fb2e..1c0ba0774687 100644
--- a/sys/dev/random/random_harvestq.c
+++ b/sys/dev/random/random_harvestq.c
@@ -75,8 +75,6 @@ __FBSDID("$FreeBSD$");
 static void random_kthread(void);
 static void random_sources_feed(void);
 
-static u_int read_rate;
-
 /*
  * Random must initialize much earlier than epoch, but we can initialize the
  * epoch code before SMP starts.  Prior to SMP, we can safely bypass
@@ -231,7 +229,7 @@ random_sources_feed(void)
 	uint32_t entropy[HARVESTSIZE];
 	struct epoch_tracker et;
 	struct random_sources *rrs;
-	u_int i, n, local_read_rate;
+	u_int i, n;
 	bool rse_warm;
 
 	rse_warm = epoch_inited;
@@ -240,15 +238,10 @@ random_sources_feed(void)
 	 * Step over all of live entropy sources, and feed their output
 	 * to the system-wide RNG.
 	 */
-	local_read_rate = atomic_readandclear_32(&read_rate);
-	/* Perform at least one read per round */
-	local_read_rate = MAX(local_read_rate, 1);
-	/* But not exceeding RANDOM_KEYSIZE_WORDS */
-	local_read_rate = MIN(local_read_rate, RANDOM_KEYSIZE_WORDS);
 	if (rse_warm)
 		epoch_enter_preempt(rs_epoch, &et);
 	CK_LIST_FOREACH(rrs, &source_list, rrs_entries) {
-		for (i = 0; i < p_random_alg_context->ra_poolcount*local_read_rate; i++) {
+		for (i = 0; i < p_random_alg_context->ra_poolcount; i++) {
 			n = rrs->rrs_source->rs_read(entropy, sizeof(entropy));
 			KASSERT((n <= sizeof(entropy)), ("%s: rs_read returned too much data (%u > %zu)", __func__, n, sizeof(entropy)));
 			/*
@@ -276,7 +269,7 @@ void
 read_rate_increment(u_int chunk)
 {
 
-	atomic_add_32(&read_rate, chunk);
+	/* Stubbed to maintain KBI; removed in FreeBSD 14.0. */
 }
 
 /* ARGSUSED */
diff --git a/sys/dev/random/randomdev.c b/sys/dev/random/randomdev.c
index 114246415aa6..4b032cd3feb9 100644
--- a/sys/dev/random/randomdev.c
+++ b/sys/dev/random/randomdev.c
@@ -187,7 +187,6 @@ int
 	if (error != 0)
 		return (error);
 
-	read_rate_increment(howmany(uio->uio_resid + 1, sizeof(uint32_t)));
 	total_read = 0;
 
 	/* Easy to deal with the trivial 0 byte case. */
@@ -286,7 +285,6 @@ void
 
 		(void)randomdev_wait_until_seeded(SEEDWAIT_UNINTERRUPTIBLE);
 	}
-	read_rate_increment(roundup2(len, sizeof(uint32_t)));
 	p_random_alg_context->ra_read(random_buf, len);
 }