Module Name: src
Committed By: tls
Date: Tue Apr 10 14:02:28 UTC 2012
Modified Files:
src/sys/kern: kern_rndq.c subr_cprng.c
src/sys/lib/libkern: arc4random.c
src/sys/sys: rnd.h
Log Message:
Add a spin mutex to the rndsink structure; it is used to avoid lock
ordering and sleep-holding-locks problems when rekeying, and thus
to avoid a nasty race between cprng destruction and reseeding.
To generate a diff of this commit:
cvs rdiff -u -r1.1 -r1.2 src/sys/kern/kern_rndq.c
cvs rdiff -u -r1.5 -r1.6 src/sys/kern/subr_cprng.c
cvs rdiff -u -r1.31 -r1.32 src/sys/lib/libkern/arc4random.c
cvs rdiff -u -r1.29 -r1.30 src/sys/sys/rnd.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:1.1 src/sys/kern/kern_rndq.c:1.2
--- src/sys/kern/kern_rndq.c:1.1 Thu Feb 2 19:43:07 2012
+++ src/sys/kern/kern_rndq.c Tue Apr 10 14:02:27 2012
@@ -1,4 +1,4 @@
-/* $NetBSD: kern_rndq.c,v 1.1 2012/02/02 19:43:07 tls Exp $ */
+/* $NetBSD: kern_rndq.c,v 1.2 2012/04/10 14:02:27 tls Exp $ */
/*-
* Copyright (c) 1997-2011 The NetBSD Foundation, Inc.
@@ -32,7 +32,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_rndq.c,v 1.1 2012/02/02 19:43:07 tls Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_rndq.c,v 1.2 2012/04/10 14:02:27 tls Exp $");
#include <sys/param.h>
#include <sys/ioctl.h>
@@ -109,13 +109,17 @@ volatile int rnd_timeout_pending;
SIMPLEQ_HEAD(, _rnd_sample_t) rnd_samples;
kmutex_t rnd_mtx;
+
/*
* Entropy sinks: usually other generators waiting to be rekeyed.
*
* A sink's callback MUST NOT re-add the sink to the list, or
- * list corruption will occur.
+ * list corruption will occur. The list is protected by the
+ * rndsink_mtx, which must be released before calling any sink's
+ * callback.
*/
TAILQ_HEAD(, rndsink) rnd_sinks;
+kmutex_t rndsink_mtx;
/*
* Memory pool for sample buffers
@@ -215,6 +219,7 @@ rnd_wakeup_readers(void)
/*
* First, take care of in-kernel consumers needing rekeying.
*/
+ mutex_spin_enter(&rndsink_mtx);
TAILQ_FOREACH_SAFE(sink, &rnd_sinks, tailq, tsink) {
if ((sink->len + RND_ENTROPY_THRESHOLD) * 8 <
rndpool_get_entropy_count(&rnd_pool)) {
@@ -225,11 +230,16 @@ rnd_wakeup_readers(void)
panic("could not extract estimated "
"entropy from pool");
}
+ /* Skip if busy, else mark in-progress */
+ if (!mutex_tryenter(&sink->mtx)) {
+ continue;
+ }
/* Move this sink to the list of pending callbacks */
TAILQ_REMOVE(&rnd_sinks, sink, tailq);
TAILQ_INSERT_HEAD(&sunk, sink, tailq);
}
}
+ mutex_spin_exit(&rndsink_mtx);
/*
* If we still have enough new bits to do something, feed userspace.
@@ -261,6 +271,7 @@ rnd_wakeup_readers(void)
#endif
sink->cb(sink->arg);
TAILQ_REMOVE(&sunk, sink, tailq);
+ mutex_spin_exit(&sink->mtx);
}
}
@@ -362,6 +373,7 @@ rnd_init(void)
return;
mutex_init(&rnd_mtx, MUTEX_DEFAULT, IPL_VM);
+ mutex_init(&rndsink_mtx, MUTEX_DEFAULT, IPL_VM);
callout_init(&rnd_callout, CALLOUT_MPSAFE);
callout_setfunc(&rnd_callout, rnd_timeout, NULL);
@@ -962,9 +974,12 @@ rndsink_attach(rndsink_t *rs)
printf("rnd: entropy sink \"%s\" wants %d bytes of data.\n",
rs->name, (int)rs->len);
#endif
- mutex_spin_enter(&rndpool_mtx);
+
+ KASSERT(mutex_owned(&rs->mtx));
+
+ mutex_spin_enter(&rndsink_mtx);
TAILQ_INSERT_TAIL(&rnd_sinks, rs, tailq);
- mutex_spin_exit(&rndpool_mtx);
+ mutex_spin_exit(&rndsink_mtx);
mutex_spin_enter(&rnd_mtx);
if (rnd_timeout_pending == 0) {
rnd_timeout_pending = 1;
@@ -980,13 +995,16 @@ rndsink_detach(rndsink_t *rs)
#ifdef RND_VERBOSE
printf("rnd: entropy sink \"%s\" no longer wants data.\n", rs->name);
#endif
- mutex_spin_enter(&rndpool_mtx);
+
+ KASSERT(mutex_owned(&rs->mtx));
+
+ mutex_spin_enter(&rndsink_mtx);
TAILQ_FOREACH_SAFE(sink, &rnd_sinks, tailq, tsink) {
if (sink == rs) {
TAILQ_REMOVE(&rnd_sinks, rs, tailq);
}
}
- mutex_spin_exit(&rndpool_mtx);
+ mutex_spin_exit(&rndsink_mtx);
}
void
Index: src/sys/kern/subr_cprng.c
diff -u src/sys/kern/subr_cprng.c:1.5 src/sys/kern/subr_cprng.c:1.6
--- src/sys/kern/subr_cprng.c:1.5 Sat Dec 17 20:05:39 2011
+++ src/sys/kern/subr_cprng.c Tue Apr 10 14:02:28 2012
@@ -1,4 +1,4 @@
-/* $NetBSD: subr_cprng.c,v 1.5 2011/12/17 20:05:39 tls Exp $ */
+/* $NetBSD: subr_cprng.c,v 1.6 2012/04/10 14:02:28 tls Exp $ */
/*-
* Copyright (c) 2011 The NetBSD Foundation, Inc.
@@ -46,7 +46,7 @@
#include <sys/cprng.h>
-__KERNEL_RCSID(0, "$NetBSD: subr_cprng.c,v 1.5 2011/12/17 20:05:39 tls Exp $");
+__KERNEL_RCSID(0, "$NetBSD: subr_cprng.c,v 1.6 2012/04/10 14:02:28 tls Exp $");
void
cprng_init(void)
@@ -75,10 +75,11 @@ static void
cprng_strong_sched_reseed(cprng_strong_t *const c)
{
KASSERT(mutex_owned(&c->mtx));
- if (!(c->reseed_pending)) {
+ if (!(c->reseed_pending) && mutex_tryenter(&c->reseed.mtx)) {
c->reseed_pending = 1;
c->reseed.len = NIST_BLOCK_KEYLEN_BYTES;
rndsink_attach(&c->reseed);
+ mutex_spin_exit(&c->reseed.mtx);
}
}
@@ -123,6 +124,7 @@ cprng_strong_create(const char *const na
c->reseed_pending = 0;
c->reseed.cb = cprng_strong_reseed;
c->reseed.arg = c;
+ mutex_init(&c->reseed.mtx, MUTEX_DEFAULT, IPL_VM);
strlcpy(c->reseed.name, name, sizeof(c->reseed.name));
mutex_init(&c->mtx, MUTEX_DEFAULT, ipl);
@@ -266,6 +268,7 @@ cprng_strong(cprng_strong_t *const c, vo
void
cprng_strong_destroy(cprng_strong_t *c)
{
+ mutex_spin_enter(&c->reseed.mtx);
mutex_enter(&c->mtx);
if (c->flags & CPRNG_USE_CV) {
@@ -277,6 +280,8 @@ cprng_strong_destroy(cprng_strong_t *c)
if (c->reseed_pending) {
rndsink_detach(&c->reseed);
}
+ mutex_spin_exit(&c->reseed.mtx);
+
nist_ctr_drbg_destroy(&c->drbg);
mutex_exit(&c->mtx);
Index: src/sys/lib/libkern/arc4random.c
diff -u src/sys/lib/libkern/arc4random.c:1.31 src/sys/lib/libkern/arc4random.c:1.32
--- src/sys/lib/libkern/arc4random.c:1.31 Tue Feb 14 18:57:35 2012
+++ src/sys/lib/libkern/arc4random.c Tue Apr 10 14:02:28 2012
@@ -1,4 +1,4 @@
-/* $NetBSD: arc4random.c,v 1.31 2012/02/14 18:57:35 njoly Exp $ */
+/* $NetBSD: arc4random.c,v 1.32 2012/04/10 14:02:28 tls Exp $ */
/*-
* Copyright (c) 2002, 2011 The NetBSD Foundation, Inc.
@@ -167,7 +167,9 @@ arc4_randrekey(void *arg)
"forcibly rekeying.\n");
r = rnd_extract_data(key, ARC4_KEYBYTES,
RND_EXTRACT_ANY);
+ mutex_spin_enter(&rs.mtx);
rndsink_detach(&rs);
+ mutex_spin_exit(&rs.mtx);
callback_pending = 0;
goto got_entropy;
} else {
@@ -195,11 +197,13 @@ got_entropy:
callback_pending = 0;
} else if (!callback_pending) {
callback_pending = 1;
+ mutex_spin_enter(&rs.mtx);
strlcpy(rs.name, "arc4random", sizeof(rs.name));
rs.cb = arc4_randrekey;
rs.arg = &rs;
rs.len = ARC4_KEYBYTES;
rndsink_attach(&rs);
+ mutex_spin_exit(&rs.mtx);
}
#endif
/*
@@ -260,6 +264,7 @@ arc4_init(void)
int n;
mutex_init(&arc4_mtx, MUTEX_DEFAULT, IPL_VM);
+ mutex_init(&rs.mtx, MUTEX_DEFAULT, IPL_VM);
arc4_i = arc4_j = 0;
for (n = 0; n < 256; n++)
arc4_sbox[n] = (u_int8_t) n;
Index: src/sys/sys/rnd.h
diff -u src/sys/sys/rnd.h:1.29 src/sys/sys/rnd.h:1.30
--- src/sys/sys/rnd.h:1.29 Thu Feb 2 19:43:08 2012
+++ src/sys/sys/rnd.h Tue Apr 10 14:02:28 2012
@@ -1,4 +1,4 @@
-/* $NetBSD: rnd.h,v 1.29 2012/02/02 19:43:08 tls Exp $ */
+/* $NetBSD: rnd.h,v 1.30 2012/04/10 14:02:28 tls Exp $ */
/*-
* Copyright (c) 1997 The NetBSD Foundation, Inc.
@@ -129,6 +129,7 @@ typedef struct krndsource {
typedef struct rndsink {
TAILQ_ENTRY(rndsink) tailq; /* the queue */
+ kmutex_t mtx; /* lock to seed or unregister */
void (*cb)(void *); /* callback function when ready */
void *arg; /* callback function argument */
char name[16]; /* sink name */
