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Date:      Thu, 2 Aug 2012 13:57:50 +0000 (UTC)
From:      Gleb Smirnoff <glebius@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r238990 - in head/sys: net netinet netinet6
Message-ID:  <201208021357.q72DvoFJ088426@svn.freebsd.org>

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Author: glebius
Date: Thu Aug  2 13:57:49 2012
New Revision: 238990
URL: http://svn.freebsd.org/changeset/base/238990

Log:
  Fix races between in_lltable_prefix_free(), lla_lookup(),
  llentry_free() and arptimer():
  
  o Use callout_init_rw() for lle timeout, this allows us safely
    disestablish them.
    - This allows us to simplify the arptimer() and make it
      race safe.
  o Consistently use ifp->if_afdata_lock to lock access to
    linked lists in the lle hashes.
  o Introduce new lle flag LLE_LINKED, which marks an entry that
    is attached to the hash.
    - Use LLE_LINKED to avoid double unlinking via consequent
      calls to llentry_free().
    - Mark lle with LLE_DELETED via |= operation istead of =,
      so that other flags won't be lost.
  o Make LLE_ADDREF(), LLE_REMREF() and LLE_FREE_LOCKED() more
    consistent and provide more informative KASSERTs.
  
  The patch is a collaborative work of all submitters and myself.
  
  PR:		kern/165863
  Submitted by:	Andrey Zonov <andrey zonov.org>
  Submitted by:	Ryan Stone <rysto32 gmail.com>
  Submitted by:	Eric van Gyzen <eric_van_gyzen dell.com>

Modified:
  head/sys/net/if_llatbl.c
  head/sys/net/if_llatbl.h
  head/sys/net/if_var.h
  head/sys/netinet/if_ether.c
  head/sys/netinet/in.c
  head/sys/netinet6/in6.c

Modified: head/sys/net/if_llatbl.c
==============================================================================
--- head/sys/net/if_llatbl.c	Thu Aug  2 13:20:44 2012	(r238989)
+++ head/sys/net/if_llatbl.c	Thu Aug  2 13:57:49 2012	(r238990)
@@ -106,10 +106,19 @@ llentry_free(struct llentry *lle)
 	size_t pkts_dropped;
 	struct mbuf *next;
 
-	pkts_dropped = 0;
+	IF_AFDATA_WLOCK_ASSERT(lle->lle_tbl->llt_ifp);
 	LLE_WLOCK_ASSERT(lle);
+
+	/* XXX: guard against race with other llentry_free(). */
+	if (!(lle->la_flags & LLE_LINKED)) {
+		LLE_FREE_LOCKED(lle);
+		return (0);
+	}
+
 	LIST_REMOVE(lle, lle_next);
+	lle->la_flags &= ~(LLE_VALID | LLE_LINKED);
 
+	pkts_dropped = 0;
 	while ((lle->la_numheld > 0) && (lle->la_hold != NULL)) {
 		next = lle->la_hold->m_nextpkt;
 		m_freem(lle->la_hold);
@@ -122,7 +131,6 @@ llentry_free(struct llentry *lle)
 		("%s: la_numheld %d > 0, pkts_droped %zd", __func__,
 		 lle->la_numheld, pkts_dropped));
 
-	lle->la_flags &= ~LLE_VALID;
 	LLE_FREE_LOCKED(lle);
 
 	return (pkts_dropped);
@@ -173,17 +181,16 @@ lltable_free(struct lltable *llt)
 	SLIST_REMOVE(&V_lltables, llt, lltable, llt_link);
 	LLTABLE_WUNLOCK();
 
+	IF_AFDATA_WLOCK(llt->llt_ifp);
 	for (i = 0; i < LLTBL_HASHTBL_SIZE; i++) {
 		LIST_FOREACH_SAFE(lle, &llt->lle_head[i], lle_next, next) {
-			int canceled;
-
-			canceled = callout_drain(&lle->la_timer);
 			LLE_WLOCK(lle);
-			if (canceled)
+			if (callout_stop(&lle->la_timer))
 				LLE_REMREF(lle);
 			llentry_free(lle);
 		}
 	}
+	IF_AFDATA_WUNLOCK(llt->llt_ifp);
 
 	free(llt, M_LLTABLE);
 }

Modified: head/sys/net/if_llatbl.h
==============================================================================
--- head/sys/net/if_llatbl.h	Thu Aug  2 13:20:44 2012	(r238989)
+++ head/sys/net/if_llatbl.h	Thu Aug  2 13:57:49 2012	(r238990)
@@ -103,26 +103,28 @@ struct llentry {
 #define	LLE_ADDREF(lle) do {					\
 	LLE_WLOCK_ASSERT(lle);					\
 	KASSERT((lle)->lle_refcnt >= 0,				\
-		("negative refcnt %d", (lle)->lle_refcnt));	\
+	    ("negative refcnt %d on lle %p",			\
+	    (lle)->lle_refcnt, (lle)));				\
 	(lle)->lle_refcnt++;					\
 } while (0)
 
 #define	LLE_REMREF(lle)	do {					\
 	LLE_WLOCK_ASSERT(lle);					\
-	KASSERT((lle)->lle_refcnt > 1,				\
-		("bogus refcnt %d", (lle)->lle_refcnt));	\
+	KASSERT((lle)->lle_refcnt > 0,				\
+	    ("bogus refcnt %d on lle %p",			\
+	    (lle)->lle_refcnt, (lle)));				\
 	(lle)->lle_refcnt--;					\
 } while (0)
 
 #define	LLE_FREE_LOCKED(lle) do {				\
-	if ((lle)->lle_refcnt <= 1)				\
-		(lle)->lle_free((lle)->lle_tbl, (lle));\
+	if ((lle)->lle_refcnt == 1)				\
+		(lle)->lle_free((lle)->lle_tbl, (lle));		\
 	else {							\
-		(lle)->lle_refcnt--;				\
+		LLE_REMREF(lle);				\
 		LLE_WUNLOCK(lle);				\
 	}							\
 	/* guard against invalid refs */			\
-	lle = NULL;						\
+	(lle) = NULL;						\
 } while (0)
 
 #define	LLE_FREE(lle) do {					\
@@ -172,6 +174,7 @@ MALLOC_DECLARE(M_LLTABLE);
 #define	LLE_VALID	0x0008	/* ll_addr is valid */
 #define	LLE_PROXY	0x0010	/* proxy entry ??? */
 #define	LLE_PUB		0x0020	/* publish entry ??? */
+#define	LLE_LINKED	0x0040	/* linked to lookup structure */
 #define	LLE_EXCLUSIVE	0x2000	/* return lle xlocked  */
 #define	LLE_DELETE	0x4000	/* delete on a lookup - match LLE_IFADDR */
 #define	LLE_CREATE	0x8000	/* create on a lookup miss */

Modified: head/sys/net/if_var.h
==============================================================================
--- head/sys/net/if_var.h	Thu Aug  2 13:20:44 2012	(r238989)
+++ head/sys/net/if_var.h	Thu Aug  2 13:57:49 2012	(r238990)
@@ -415,6 +415,8 @@ EVENTHANDLER_DECLARE(group_change_event,
 #define	IF_AFDATA_DESTROY(ifp)	rw_destroy(&(ifp)->if_afdata_lock)
 
 #define	IF_AFDATA_LOCK_ASSERT(ifp)	rw_assert(&(ifp)->if_afdata_lock, RA_LOCKED)
+#define	IF_AFDATA_RLOCK_ASSERT(ifp)	rw_assert(&(ifp)->if_afdata_lock, RA_RLOCKED)
+#define	IF_AFDATA_WLOCK_ASSERT(ifp)	rw_assert(&(ifp)->if_afdata_lock, RA_WLOCKED)
 #define	IF_AFDATA_UNLOCK_ASSERT(ifp)	rw_assert(&(ifp)->if_afdata_lock, RA_UNLOCKED)
 
 int	if_handoff(struct ifqueue *ifq, struct mbuf *m, struct ifnet *ifp,

Modified: head/sys/netinet/if_ether.c
==============================================================================
--- head/sys/netinet/if_ether.c	Thu Aug  2 13:20:44 2012	(r238989)
+++ head/sys/netinet/if_ether.c	Thu Aug  2 13:57:49 2012	(r238990)
@@ -163,49 +163,40 @@ arp_ifscrub(struct ifnet *ifp, uint32_t 
 static void
 arptimer(void *arg)
 {
+	struct llentry *lle = (struct llentry *)arg;
 	struct ifnet *ifp;
-	struct llentry   *lle;
-	int pkts_dropped;
+	size_t pkts_dropped;
+
+	if (lle->la_flags & LLE_STATIC) {
+		LLE_WUNLOCK(lle);
+		return;
+	}
 
-	KASSERT(arg != NULL, ("%s: arg NULL", __func__));
-	lle = (struct llentry *)arg;
 	ifp = lle->lle_tbl->llt_ifp;
 	CURVNET_SET(ifp->if_vnet);
+
+	if (lle->la_flags != LLE_DELETED) {
+		int evt;
+
+		if (lle->la_flags & LLE_VALID)
+			evt = LLENTRY_EXPIRED;
+		else
+			evt = LLENTRY_TIMEDOUT;
+		EVENTHANDLER_INVOKE(lle_event, lle, evt);
+	}
+
+	callout_stop(&lle->la_timer);
+
+	/* XXX: LOR avoidance. We still have ref on lle. */
+	LLE_WUNLOCK(lle);
 	IF_AFDATA_LOCK(ifp);
 	LLE_WLOCK(lle);
-	if (lle->la_flags & LLE_STATIC)
-		LLE_WUNLOCK(lle);
-	else {
-		if (!callout_pending(&lle->la_timer) &&
-		    callout_active(&lle->la_timer)) {
-			callout_stop(&lle->la_timer);
-			LLE_REMREF(lle);
-
-			if (lle->la_flags != LLE_DELETED) {
-				int evt;
-
-				if (lle->la_flags & LLE_VALID)
-					evt = LLENTRY_EXPIRED;
-				else
-					evt = LLENTRY_TIMEDOUT;
-				EVENTHANDLER_INVOKE(lle_event, lle, evt);
-			}
 
-			pkts_dropped = llentry_free(lle);
-			ARPSTAT_ADD(dropped, pkts_dropped);
-			ARPSTAT_INC(timeouts);
-		} else {
-#ifdef DIAGNOSTIC
-			struct sockaddr *l3addr = L3_ADDR(lle);
-			log(LOG_INFO,
-			    "arptimer issue: %p, IPv4 address: \"%s\"\n", lle,
-			    inet_ntoa(
-			        ((const struct sockaddr_in *)l3addr)->sin_addr));
-#endif
-			LLE_WUNLOCK(lle);
-		}
-	}
+	LLE_REMREF(lle);
+	pkts_dropped = llentry_free(lle);
 	IF_AFDATA_UNLOCK(ifp);
+	ARPSTAT_ADD(dropped, pkts_dropped);
+	ARPSTAT_INC(timeouts);
 	CURVNET_RESTORE();
 }
 

Modified: head/sys/netinet/in.c
==============================================================================
--- head/sys/netinet/in.c	Thu Aug  2 13:20:44 2012	(r238989)
+++ head/sys/netinet/in.c	Thu Aug  2 13:57:49 2012	(r238990)
@@ -1280,7 +1280,6 @@ in_lltable_new(const struct sockaddr *l3
 	if (lle == NULL)		/* NB: caller generates msg */
 		return NULL;
 
-	callout_init(&lle->base.la_timer, CALLOUT_MPSAFE);
 	/*
 	 * For IPv4 this will trigger "arpresolve" to generate
 	 * an ARP request.
@@ -1290,7 +1289,10 @@ in_lltable_new(const struct sockaddr *l3
 	lle->base.lle_refcnt = 1;
 	lle->base.lle_free = in_lltable_free;
 	LLE_LOCK_INIT(&lle->base);
-	return &lle->base;
+	callout_init_rw(&lle->base.la_timer, &lle->base.lle_lock,
+	    CALLOUT_RETURNUNLOCKED);
+
+	return (&lle->base);
 }
 
 #define IN_ARE_MASKED_ADDR_EQUAL(d, a, m)	(			\
@@ -1306,6 +1308,7 @@ in_lltable_prefix_free(struct lltable *l
 	int i;
 	size_t pkts_dropped;
 
+	IF_AFDATA_WLOCK(llt->llt_ifp);
 	for (i = 0; i < LLTBL_HASHTBL_SIZE; i++) {
 		LIST_FOREACH_SAFE(lle, &llt->lle_head[i], lle_next, next) {
 			/*
@@ -1315,17 +1318,15 @@ in_lltable_prefix_free(struct lltable *l
 			if (IN_ARE_MASKED_ADDR_EQUAL(satosin(L3_ADDR(lle)),
 			    pfx, msk) && ((flags & LLE_STATIC) ||
 			    !(lle->la_flags & LLE_STATIC))) {
-				int canceled;
-
-				canceled = callout_drain(&lle->la_timer);
 				LLE_WLOCK(lle);
-				if (canceled)
+				if (callout_stop(&lle->la_timer))
 					LLE_REMREF(lle);
 				pkts_dropped = llentry_free(lle);
 				ARPSTAT_ADD(dropped, pkts_dropped);
 			}
 		}
 	}
+	IF_AFDATA_WUNLOCK(llt->llt_ifp);
 }
 
 
@@ -1457,11 +1458,12 @@ in_lltable_lookup(struct lltable *llt, u
 
 		lle->lle_tbl  = llt;
 		lle->lle_head = lleh;
+		lle->la_flags |= LLE_LINKED;
 		LIST_INSERT_HEAD(lleh, lle, lle_next);
 	} else if (flags & LLE_DELETE) {
 		if (!(lle->la_flags & LLE_IFADDR) || (flags & LLE_IFADDR)) {
 			LLE_WLOCK(lle);
-			lle->la_flags = LLE_DELETED;
+			lle->la_flags |= LLE_DELETED;
 			EVENTHANDLER_INVOKE(lle_event, lle, LLENTRY_DELETED);
 			LLE_WUNLOCK(lle);
 #ifdef DIAGNOSTIC

Modified: head/sys/netinet6/in6.c
==============================================================================
--- head/sys/netinet6/in6.c	Thu Aug  2 13:20:44 2012	(r238989)
+++ head/sys/netinet6/in6.c	Thu Aug  2 13:57:49 2012	(r238990)
@@ -2497,23 +2497,22 @@ in6_lltable_prefix_free(struct lltable *
 	 * (flags & LLE_STATIC) means deleting all entries
 	 * including static ND6 entries.
 	 */
+	IF_AFDATA_WLOCK(llt->llt_ifp);
 	for (i = 0; i < LLTBL_HASHTBL_SIZE; i++) {
 		LIST_FOREACH_SAFE(lle, &llt->lle_head[i], lle_next, next) {
 			if (IN6_ARE_MASKED_ADDR_EQUAL(
-				    &((struct sockaddr_in6 *)L3_ADDR(lle))->sin6_addr,
-				    &pfx->sin6_addr,
-				    &msk->sin6_addr) &&
-			    ((flags & LLE_STATIC) || !(lle->la_flags & LLE_STATIC))) {
-				int canceled;
-
-				canceled = callout_drain(&lle->la_timer);
+			    &satosin6(L3_ADDR(lle))->sin6_addr,
+			    &pfx->sin6_addr, &msk->sin6_addr) &&
+			    ((flags & LLE_STATIC) ||
+			    !(lle->la_flags & LLE_STATIC))) {
 				LLE_WLOCK(lle);
-				if (canceled)
+				if (callout_stop(&lle->la_timer))
 					LLE_REMREF(lle);
 				llentry_free(lle);
 			}
 		}
 	}
+	IF_AFDATA_WUNLOCK(llt->llt_ifp);
 }
 
 static int
@@ -2605,11 +2604,12 @@ in6_lltable_lookup(struct lltable *llt, 
 
 		lle->lle_tbl  = llt;
 		lle->lle_head = lleh;
+		lle->la_flags |= LLE_LINKED;
 		LIST_INSERT_HEAD(lleh, lle, lle_next);
 	} else if (flags & LLE_DELETE) {
 		if (!(lle->la_flags & LLE_IFADDR) || (flags & LLE_IFADDR)) {
 			LLE_WLOCK(lle);
-			lle->la_flags = LLE_DELETED;
+			lle->la_flags |= LLE_DELETED;
 			LLE_WUNLOCK(lle);
 #ifdef DIAGNOSTIC
 			log(LOG_INFO, "ifaddr cache = %p  is deleted\n", lle);



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