pf: fix a crash on sendfile()

The network layer must not pass unmapped (M_EXTPG) mbufs to if_output()
of network interfaces without IFCAP_MEXTPG. pf should convert these
mbufs by mb_unmapped_to_ext() for such interfaces but it didn't.
The problem had occurred on sendfile because sendfile system call
uses unmapped mbufs for the file data.

Reported by:	feld
Reviewed by:	kp, glebius
Differential Revision:	https://reviews.freebsd.org/D58021

sys/netpfil/pf/pf.c

@@ -9980,6 +9980,21 @@ pf_route(struct pf_krule *r, struct ifnet *oifp,
 		pd->act.dnpipe = tmp;
 	}
 
+	/*
+	 * If the output interface does not accept unmapped mbufs, convert
+	 * them to mapped mbufs.
+	 */
+	if ((ifp->if_capenable & IFCAP_MEXTPG) == 0) {
+		error = mb_unmapped_to_ext(m0, &md);
+		if (error)
+			goto done;
+		/*
+		 * The first mbuf should not be reallocated because it is
+		 * always mapped.
+		 */
+		MPASS(m0 == md);
+	}
+
 	/*
 	 * If small enough for interface, or the interface will take
 	 * care of the fragmentation for us, we can just send directly.
@@ -10321,6 +10336,11 @@ pf_route6(struct pf_krule *r, struct ifnet *oifp,
 	}
 
 	if ((u_long)m0->m_pkthdr.len <= ifp->if_mtu) {
+		if ((ifp->if_capenable & IFCAP_MEXTPG) == 0) {
+			if (mb_unmapped_to_ext(m0, &md) != 0)
+				goto done;
+			MPASS(m0 == md);
+		}
 		md = m0;
 		pf_dummynet_route(pd, s, r, ifp, sintosa(&dst), &md);
 		if (md != NULL) {
@@ -11585,6 +11605,7 @@ pf_test(sa_family_t af, int dir, int pflags, struct ifnet *ifp, struct mbuf **m0
 {
 	struct pfi_kkif		*kif;
 	u_short			 action, reason = 0;
+	struct mbuf		*m;
 	struct m_tag		*mtag;
 	struct pf_krule		*a = NULL, *r = &V_pf_default_rule;
 	struct pf_kstate	*s = NULL;
@@ -11620,6 +11641,12 @@ pf_test(sa_family_t af, int dir, int pflags, struct ifnet *ifp, struct mbuf **m0
 	}
 
 	if (__predict_false(! M_WRITABLE(*m0))) {
+		/* Need to convert unmapped mbufs before calling m_unshare(). */
+		if (mb_unmapped_to_ext(*m0, &m) != 0) {
+			*m0 = NULL;
+			return (PF_DROP);
+		}
+		MPASS(*m0 == m);
 		*m0 = m_unshare(*m0, M_NOWAIT);
 		if (*m0 == NULL) {
 			return (PF_DROP);
@@ -11639,6 +11666,14 @@ pf_test(sa_family_t af, int dir, int pflags, struct ifnet *ifp, struct mbuf **m0
 			*m0 = NULL;
 			return (PF_PASS);
 		}
+
+		/*
+		 * No need to call mb_unmapped_to_ext() here because it had
+		 * already been called in pf_route()/pf_route6() and dummynet
+		 * re-injected this packet.
+		 */
+
+		M_ASSERTMAPPED(*m0);
 		(ifp->if_output)(ifp, *m0, sintosa(&pd.pf_mtag->dst), NULL);
 		*m0 = NULL;
 		return (PF_PASS);

tests/sys/netpfil/pf/Makefile

@@ -56,7 +56,8 @@ ATF_TESTS_SH+=	altq \
 		synproxy \
 		table \
 		tcp \
-		tos
+		tos \
+		unmapped_mbuf
 
 ATF_TESTS_PYTEST+=	frag4.py
 ATF_TESTS_PYTEST+=	frag6.py

tests/sys/netpfil/pf/unmapped_mbuf.sh

@@ -0,0 +1,145 @@
+#
+# SPDX-License-Identifier: BSD-2-Clause
+#
+# Copyright (c) 2026 KUROSAWA Takahiro <[email protected]>
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+# 1. Redistributions of source code must retain the above copyright
+#    notice, this list of conditions and the following disclaimer.
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions and the following disclaimer in the
+#    documentation and/or other materials provided with the distribution.
+#
+# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+# SUCH DAMAGE.
+
+. $(atf_get_srcdir)/utils.subr
+
+HELPER=$(atf_get_srcdir)/../../common/sendfile_helper
+
+# pf must call mb_unmapped_to_ext() before passing an output mbuf to a network
+# interface if it does not accept unmapped mbufs as ip_output() does. These
+# tests make sure that unmapped mbufs are correctly converted to mapped ones
+# before pf passes mbufs to interfaces.
+
+atf_test_case "v4" "cleanup"
+v4_head() {
+	atf_set descr 'unmapped mbuf IPv4 test'
+	atf_set require.user root
+}
+
+v4_body() {
+	pft_init
+
+	l=$(vnet_mkepair)
+	vnet_mkjail a ${l}a
+	jexec a ifconfig ${l}a 192.0.2.1/24 up
+	vnet_mkjail b ${l}b
+	jexec b ifconfig ${l}b 192.0.2.2/24 up
+
+	# Sanity check
+	atf_check -s exit:0 -o ignore jexec a ping -c 1 192.0.2.2
+
+	jexec a pfctl -e
+	pft_set_rules a "pass out on ${l}a route-to (${l}a 192.0.2.2) all"
+	jexec b timeout 30s nc -4 -d -l 2345 > out &
+	sleep 1
+	atf_check -s exit:0 -o ignore \
+	    jexec a ${HELPER} -c 192.0.2.2 -p 2345 ${HELPER} 0 512 0
+	wait
+	atf_check_equal $(dd bs=512 count=1 if=${HELPER} | sha256 -q) \
+	    $(sha256 -q out)
+}
+
+v4_cleanup() {
+	pft_cleanup
+	rm -f out
+}
+
+atf_test_case "v6" "cleanup"
+v6_head() {
+	atf_set descr 'unmapped mbuf IPv6 test'
+	atf_set require.user root
+}
+
+v6_body() {
+	pft_init
+
+	l=$(vnet_mkepair)
+	vnet_mkjail a ${l}a
+	jexec a ifconfig ${l}a inet6 2001:db8::1/64 up
+	vnet_mkjail b ${l}b
+	jexec b ifconfig ${l}b inet6 2001:db8::2/64 up
+
+	# Sanity check
+	atf_check -s exit:0 -o ignore jexec a ping -c 1 2001:db8::2
+
+	jexec a pfctl -e
+	pft_set_rules a "pass out on ${l}a route-to (${l}a 2001:db8::2) all"
+	jexec b timeout 30s nc -6 -d -l 2345 > out &
+	sleep 1
+	atf_check -s exit:0 -o ignore \
+	    jexec a ${HELPER} -c 2001:db8::2 -p 2345 ${HELPER} 0 512 0
+	wait
+	atf_check_equal $(dd bs=512 count=1 if=${HELPER} | sha256 -q) \
+	    $(sha256 -q out)
+}
+
+v6_cleanup() {
+	pft_cleanup
+	rm -f out
+}
+
+atf_test_case "dummynet" "cleanup"
+dummynet_head() {
+	atf_set descr 'unmapped mbuf dummynet test'
+	atf_set require.user root
+}
+
+dummynet_body() {
+	pft_init
+
+	l=$(vnet_mkepair)
+	vnet_mkjail a ${l}a
+	jexec a ifconfig ${l}a 192.0.2.1/24 up
+	vnet_mkjail b ${l}b
+	jexec b ifconfig ${l}b 192.0.2.2/24 up
+
+	# Sanity check
+	atf_check -s exit:0 -o ignore jexec a ping -c 1 192.0.2.2
+
+	atf_check -s exit:0 -o ignore \
+	    jexec a dnctl pipe 1 config delay 100
+	jexec a pfctl -e
+	pft_set_rules a "pass out on ${l}a route-to (${l}a 192.0.2.2) all dnpipe 1"
+	jexec b timeout 30s nc -4 -d -l 2345 > out &
+	sleep 1
+	atf_check -s exit:0 -o ignore \
+	    jexec a ${HELPER} -c 192.0.2.2 -p 2345 ${HELPER} 0 512 0
+	wait
+	atf_check_equal $(dd bs=512 count=1 if=${HELPER} | sha256 -q) \
+	    $(sha256 -q out)
+}
+
+dummynet_cleanup() {
+	pft_cleanup
+	rm -f out
+}
+
+atf_init_test_cases()
+{
+	atf_add_test_case "v4"
+	atf_add_test_case "v6"
+	atf_add_test_case "dummynet"
+}