Fix possible use after free due to security policy deletion.

When we are passing mbuf to IPSec processing via ipsec[46]_process_packet(),
we hold one reference to security policy and release it just after return
from this function. But IPSec processing can be deffered and when we release
reference to security policy after ipsec[46]_process_packet(), user can
delete this security policy from SPDB. And when IPSec processing will be
done, xform's callback function will do access to already freed memory.

To fix this move KEY_FREESP() into callback function. Now IPSec code will
release reference to SP after processing will be finished.

Differential Revision:	https://reviews.freebsd.org/D2324
No objections from:	#network
Sponsored by:	Yandex LLC

sys/netinet/ip_ipsec.c

@@ -199,6 +199,9 @@ ip_ipsec_output(struct mbuf **m, struct inpcb *inp, int *error)
 
 		/* NB: callee frees mbuf */
 		*error = ipsec4_process_packet(*m, sp->req);
+		/* Release SP if an error occured */
+		if (*error != 0)
+			KEY_FREESP(&sp);
 		if (*error == EJUSTRETURN) {
 			/*
 			 * We had a SP with a level of 'use' and no SA. We
@@ -238,9 +241,7 @@ ip_ipsec_output(struct mbuf **m, struct inpcb *inp, int *error)
 		KEY_FREESP(&sp);
 	return 0;
 reinjected:
-	if (sp != NULL)
-		KEY_FREESP(&sp);
-	return -1;
+	return (-1);
 bad:
 	if (sp != NULL)
 		KEY_FREESP(&sp);

sys/netinet6/ip6_forward.c

@@ -248,8 +248,7 @@ ip6_forward(struct mbuf *m, int srcrt)
 
 	/*
 	 * when the kernel forwards a packet, it is not proper to apply
-	 * IPsec transport mode to the packet is not proper.  this check
-	 * avoid from this.
+	 * IPsec transport mode to the packet. This check avoid from this.
 	 * at present, if there is even a transport mode SA request in the
 	 * security policy, the kernel does not apply IPsec to the packet.
 	 * this check is not enough because the following case is valid.
@@ -283,9 +282,9 @@ ip6_forward(struct mbuf *m, int srcrt)
 	 * ipsec6_proces_packet will send the packet using ip6_output
 	 */
 	error = ipsec6_process_packet(m, sp->req);
-
-	KEY_FREESP(&sp);
-
+	/* Release SP if an error occured */
+	if (error != 0)
+		KEY_FREESP(&sp);
 	if (error == EJUSTRETURN) {
 		/*
 		 * We had a SP with a level of 'use' and no SA. We

sys/netinet6/ip6_ipsec.c

@@ -213,7 +213,9 @@ ip6_ipsec_output(struct mbuf **m, struct inpcb *inp, int *error)
 
 		/* NB: callee frees mbuf */
 		*error = ipsec6_process_packet(*m, sp->req);
-
+		/* Release SP if an error occured */
+		if (*error != 0)
+			KEY_FREESP(&sp);
 		if (*error == EJUSTRETURN) {
 			/*
 			 * We had a SP with a level of 'use' and no SA. We
@@ -253,9 +255,7 @@ ip6_ipsec_output(struct mbuf **m, struct inpcb *inp, int *error)
 		KEY_FREESP(&sp);
 	return 0;
 reinjected:
-	if (sp != NULL)
-		KEY_FREESP(&sp);
-	return -1;
+	return (-1);
 bad:
 	if (sp != NULL)
 		KEY_FREESP(&sp);

sys/netipsec/ipsec_output.c

@@ -104,6 +104,7 @@ ipsec_process_done(struct mbuf *m, struct ipsecrequest *isr)
 
 	IPSEC_ASSERT(m != NULL, ("null mbuf"));
 	IPSEC_ASSERT(isr != NULL, ("null ISR"));
+	IPSEC_ASSERT(isr->sp != NULL, ("NULL isr->sp"));
 	sav = isr->sav;
 	IPSEC_ASSERT(sav != NULL, ("null SA"));
 	IPSEC_ASSERT(sav->sah != NULL, ("null SAH"));
@@ -163,6 +164,10 @@ ipsec_process_done(struct mbuf *m, struct ipsecrequest *isr)
 	 * If this is a problem we'll need to introduce a queue
 	 * to set the packet on so we can unwind the stack before
 	 * doing further processing.
+	 *
+	 * If ipsec[46]_process_packet() will successfully queue
+	 * the request, we need to take additional reference to SP,
+	 * because xform callback will release reference.
 	 */
 	if (isr->next) {
 		/* XXX-BZ currently only support same AF bundles. */
@@ -170,7 +175,11 @@ ipsec_process_done(struct mbuf *m, struct ipsecrequest *isr)
 #ifdef INET
 		case AF_INET:
 			IPSECSTAT_INC(ips_out_bundlesa);
-			return ipsec4_process_packet(m, isr->next);
+			key_addref(isr->sp);
+			error = ipsec4_process_packet(m, isr->next);
+			if (error != 0)
+				KEY_FREESP(&isr->sp);
+			return (error);
 			/* NOTREACHED */
 #endif
 #ifdef notyet
@@ -178,7 +187,11 @@ ipsec_process_done(struct mbuf *m, struct ipsecrequest *isr)
 		case AF_INET6:
 			/* XXX */
 			IPSEC6STAT_INC(ips_out_bundlesa);
-			return ipsec6_process_packet(m, isr->next);
+			key_addref(isr->sp);
+			error = ipsec6_process_packet(m, isr->next);
+			if (error != 0)
+				KEY_FREESP(&isr->sp);
+			return (error);
 			/* NOTREACHED */
 #endif /* INET6 */
 #endif

sys/netipsec/xform_ah.c

@@ -1091,6 +1091,7 @@ ah_output_cb(struct cryptop *crp)
 	m = (struct mbuf *) crp->crp_buf;
 
 	isr = tc->tc_isr;
+	IPSEC_ASSERT(isr->sp != NULL, ("NULL isr->sp"));
 	IPSECREQUEST_LOCK(isr);
 	sav = tc->tc_sav;
 	/* With the isr lock released SA pointer can be updated. */
@@ -1154,16 +1155,18 @@ ah_output_cb(struct cryptop *crp)
 	error = ipsec_process_done(m, isr);
 	KEY_FREESAV(&sav);
 	IPSECREQUEST_UNLOCK(isr);
-	return error;
+	KEY_FREESP(&isr->sp);
+	return (error);
 bad:
 	if (sav)
 		KEY_FREESAV(&sav);
 	IPSECREQUEST_UNLOCK(isr);
+	KEY_FREESP(&isr->sp);
 	if (m)
 		m_freem(m);
 	free(tc, M_XDATA);
 	crypto_freereq(crp);
-	return error;
+	return (error);
 }
 
 static struct xformsw ah_xformsw = {

sys/netipsec/xform_esp.c

@@ -888,6 +888,7 @@ esp_output_cb(struct cryptop *crp)
 	m = (struct mbuf *) crp->crp_buf;
 
 	isr = tc->tc_isr;
+	IPSEC_ASSERT(isr->sp != NULL, ("NULL isr->sp"));
 	IPSECREQUEST_LOCK(isr);
 	sav = tc->tc_sav;
 	/* With the isr lock released SA pointer can be updated. */
@@ -966,16 +967,18 @@ esp_output_cb(struct cryptop *crp)
 	error = ipsec_process_done(m, isr);
 	KEY_FREESAV(&sav);
 	IPSECREQUEST_UNLOCK(isr);
-	return error;
+	KEY_FREESP(&isr->sp);
+	return (error);
 bad:
 	if (sav)
 		KEY_FREESAV(&sav);
 	IPSECREQUEST_UNLOCK(isr);
+	KEY_FREESP(&isr->sp);
 	if (m)
 		m_freem(m);
 	free(tc, M_XDATA);
 	crypto_freereq(crp);
-	return error;
+	return (error);
 }
 
 static struct xformsw esp_xformsw = {

sys/netipsec/xform_ipcomp.c

@@ -492,6 +492,7 @@ ipcomp_output_cb(struct cryptop *crp)
 	skip = tc->tc_skip;
 
 	isr = tc->tc_isr;
+	IPSEC_ASSERT(isr->sp != NULL, ("NULL isr->sp"));
 	IPSECREQUEST_LOCK(isr);
 	sav = tc->tc_sav;
 	/* With the isr lock released SA pointer can be updated. */
@@ -606,16 +607,18 @@ ipcomp_output_cb(struct cryptop *crp)
 	error = ipsec_process_done(m, isr);
 	KEY_FREESAV(&sav);
 	IPSECREQUEST_UNLOCK(isr);
-	return error;
+	KEY_FREESP(&isr->sp);
+	return (error);
 bad:
 	if (sav)
 		KEY_FREESAV(&sav);
 	IPSECREQUEST_UNLOCK(isr);
+	KEY_FREESP(&isr->sp);
 	if (m)
 		m_freem(m);
 	free(tc, M_XDATA);
 	crypto_freereq(crp);
-	return error;
+	return (error);
 }
 
 static struct xformsw ipcomp_xformsw = {