Module Name: src
Committed By: riastradh
Date: Wed Feb 17 00:43:43 UTC 2016
Modified Files:
src/sys/kern: kern_rndq.c
src/sys/sys: rndsource.h
Log Message:
Add rnd_add_data_sync for synchronous on-demand rndsource callbacks.
Avoids lock recursion in rndsinks:
rndsink user holds lock
calls rndsink_request
calls rnd_getmore
calls an rndsource callback
calls rnd_add_data
calls rnd_process_events
calls rndsinks_distribute
calls rndsink callback
acquires rndsink user lock.
This can happen only before the rnd_process_events softint is
established, but that's enough to cause a problem and is the main
reason why all our HWRNG drivers are so byzantine (soon to be
fixed!).
ok tls
To generate a diff of this commit:
cvs rdiff -u -r1.75 -r1.76 src/sys/kern/kern_rndq.c
cvs rdiff -u -r1.4 -r1.5 src/sys/sys/rndsource.h
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/kern/kern_rndq.c
diff -u src/sys/kern/kern_rndq.c:1.75 src/sys/kern/kern_rndq.c:1.76
--- src/sys/kern/kern_rndq.c:1.75 Mon Jan 11 14:55:52 2016
+++ src/sys/kern/kern_rndq.c Wed Feb 17 00:43:42 2016
@@ -1,4 +1,4 @@
-/* $NetBSD: kern_rndq.c,v 1.75 2016/01/11 14:55:52 tls Exp $ */
+/* $NetBSD: kern_rndq.c,v 1.76 2016/02/17 00:43:42 riastradh Exp $ */
/*-
* Copyright (c) 1997-2013 The NetBSD Foundation, Inc.
@@ -32,7 +32,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_rndq.c,v 1.75 2016/01/11 14:55:52 tls Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_rndq.c,v 1.76 2016/02/17 00:43:42 riastradh Exp $");
#include <sys/param.h>
#include <sys/atomic.h>
@@ -156,7 +156,7 @@ static void rnd_intr(void *);
static void rnd_wake(void *);
static void rnd_process_events(void);
static void rnd_add_data_ts(krndsource_t *, const void *const,
- uint32_t, uint32_t, uint32_t);
+ uint32_t, uint32_t, uint32_t, bool);
static inline void rnd_schedule_process(void);
int rnd_ready = 0;
@@ -299,6 +299,18 @@ rnd_getmore(size_t byteswanted)
rs->name, byteswanted);
}
mutex_spin_exit(&rnd_global.lock);
+
+ /*
+ * Assume some callback is likely to have entered entropy
+ * synchronously. In that case, we may need to distribute
+ * entropy to waiters. Do that, if we can do it
+ * asynchronously. (Otherwise we may end up trying to
+ * distribute to the very rndsink that is trying to get more
+ * entropy in the first place, leading to lock recursion in
+ * that rndsink's callback.)
+ */
+ if (__predict_true(rnd_process))
+ rnd_schedule_process();
}
/*
@@ -789,7 +801,7 @@ _rnd_add_uint32(krndsource_t *rs, uint32
*/
entropy = rnd_estimate(rs, ts, val);
- rnd_add_data_ts(rs, &val, sizeof(val), entropy, ts);
+ rnd_add_data_ts(rs, &val, sizeof(val), entropy, ts, true);
}
void
@@ -813,7 +825,7 @@ _rnd_add_uint64(krndsource_t *rs, uint64
*/
entropy = rnd_estimate(rs, ts, (uint32_t)(val & (uint64_t)0xffffffff));
- rnd_add_data_ts(rs, &val, sizeof(val), entropy, ts);
+ rnd_add_data_ts(rs, &val, sizeof(val), entropy, ts, true);
}
void
@@ -831,13 +843,22 @@ rnd_add_data(krndsource_t *rs, const voi
rndpool_add_data(&rnd_global.pool, data, len, entropy);
mutex_spin_exit(&rnd_global.lock);
} else {
- rnd_add_data_ts(rs, data, len, entropy, rnd_counter());
+ rnd_add_data_ts(rs, data, len, entropy, rnd_counter(), true);
}
}
+void
+rnd_add_data_sync(krndsource_t *rs, const void *data, uint32_t len,
+ uint32_t entropy)
+{
+
+ KASSERT(rs != NULL);
+ rnd_add_data_ts(rs, data, len, entropy, rnd_counter(), false);
+}
+
static void
rnd_add_data_ts(krndsource_t *rs, const void *const data, uint32_t len,
- uint32_t entropy, uint32_t ts)
+ uint32_t entropy, uint32_t ts, bool schedule)
{
rnd_sample_t *state = NULL;
const uint8_t *p = data;
@@ -942,8 +963,9 @@ rnd_add_data_ts(krndsource_t *rs, const
}
mutex_spin_exit(&rnd_samples.lock);
- /* Cause processing of queued samples */
- rnd_schedule_process();
+ /* Cause processing of queued samples, if caller wants it. */
+ if (schedule)
+ rnd_schedule_process();
}
static int
Index: src/sys/sys/rndsource.h
diff -u src/sys/sys/rndsource.h:1.4 src/sys/sys/rndsource.h:1.5
--- src/sys/sys/rndsource.h:1.4 Tue Feb 16 23:07:58 2016
+++ src/sys/sys/rndsource.h Wed Feb 17 00:43:43 2016
@@ -1,4 +1,4 @@
-/* $NetBSD: rndsource.h,v 1.4 2016/02/16 23:07:58 riastradh Exp $ */
+/* $NetBSD: rndsource.h,v 1.5 2016/02/17 00:43:43 riastradh Exp $ */
/*-
* Copyright (c) 1997 The NetBSD Foundation, Inc.
@@ -89,6 +89,8 @@ void _rnd_add_uint32(krndsource_t *, ui
void _rnd_add_uint64(krndsource_t *, uint64_t);
void rnd_add_data(krndsource_t *, const void *const, uint32_t,
uint32_t);
+void rnd_add_data_sync(krndsource_t *, const void *, uint32_t,
+ uint32_t);
void rnd_attach_source(krndsource_t *, const char *,
uint32_t, uint32_t);
void rnd_detach_source(krndsource_t *);
