fusefs: fix a panic in vop_close with a CTL consumer

Kernel consumers like CTL may lack ucred objects.  That led to a panic
when CTL closed a fuse file, if atime was enabled on the mountpoint.
Fix it by checking the ucred during close.

PR:		283402
MFC after:	2 weeks
Sponsored by:	ConnectWise
Differential Revision: https://reviews.freebsd.org/D48165

sys/fs/fuse/fuse_vnops.c

@@ -796,6 +796,9 @@ fuse_vnop_close(struct vop_close_args *ap)
 	if (fflag & IO_NDELAY)
 		return 0;
 
+	if (cred == NULL)
+		cred = td->td_ucred;
+
 	err = fuse_flush(vp, cred, pid, fflag);
 	if (err == 0 && (fvdat->flag & FN_ATIMECHANGE) && !vfs_isrdonly(mp)) {
 		struct vattr vap;

tests/sys/cam/ctl/ctl.subr

@@ -80,7 +80,20 @@ find_device() {
 	done
 }
 
-# Create a CTL LUN
+# Create a CTL LUN backed by a file
+create_block() {
+	EXTRA_ARGS=$*
+
+	atf_check -o save:lun-create.txt ctladm create -b block $EXTRA_ARGS
+	atf_check egrep -q "LUN created successfully" lun-create.txt
+	LUN=`awk '/LUN ID:/ {print $NF}' lun-create.txt`
+	if [ -z "$LUN" ]; then
+		atf_fail "Could not find LUN id"
+	fi
+	find_device $LUN
+}
+
+# Create a CTL LUN backed by RAM
 create_ramdisk() {
 	EXTRA_ARGS=$*
 
@@ -95,7 +108,8 @@ create_ramdisk() {
 
 cleanup() {
 	if [ -e "lun-create.txt" ]; then
+		backend=`awk '/backend:/ {print $NF}' lun-create.txt`
 		lun_id=`awk '/LUN ID:/ {print $NF}' lun-create.txt`
-		ctladm remove -b ramdisk -l $lun_id > /dev/null
+		ctladm remove -b $backend -l $lun_id > /dev/null
 	fi
 }

tests/sys/fs/fusefs/Makefile

@@ -4,6 +4,8 @@ PACKAGE=	tests
 
 TESTSDIR=	${TESTSBASE}/sys/fs/fusefs
 
+ATF_TESTS_SH+=	ctl
+
 # We could simply link all of these files into a single executable.  But since
 # Kyua treats googletest programs as plain tests, it's better to separate them
 # out, so we get more granular reporting.
@@ -64,6 +66,9 @@ TEST_METADATA.default_permissions+=	required_user="unprivileged"
 TEST_METADATA.default_permissions_privileged+=	required_user="root"
 TEST_METADATA.mknod+=	required_user="root"
 TEST_METADATA.nfs+=	required_user="root"
+# ctl must be exclusive because it disables/enables camsim
+TEST_METADATA.ctl+=	is_exclusive="true"
+TEST_METADATA.ctl+=	required_user="root"
 
 TEST_METADATA+= timeout=10
 

tests/sys/fs/fusefs/ctl.sh

@@ -0,0 +1,69 @@
+# SPDX-License-Identifier: BSD-2-Clause
+#
+# Copyright (c) 2024 ConnectWise
+# All rights reserved.
+#
+# 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 DOCUMENTATION IS PROVIDED BY THE AUTHOR ``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 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.
+
+. $(atf_get_srcdir)/../../cam/ctl/ctl.subr
+
+# Regression test for https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=283402
+#
+# Almost any fuse file system would work, but this tests uses fusefs-ext2
+# because it's simple and its download is very small.
+atf_test_case remove_lun_with_atime cleanup
+remove_lun_with_atime_head()
+{
+	atf_set "descr" "Remove a fuse-backed CTL LUN when atime is enabled"
+	atf_set "require.user" "root"
+	atf_set "require.progs" "fuse-ext2 mkfs.ext2"
+}
+remove_lun_with_atime_body()
+{
+	MOUNTPOINT=$PWD/mnt
+	atf_check mkdir $MOUNTPOINT
+	atf_check truncate -s 1g ext2.img
+	atf_check mkfs.ext2 -q ext2.img
+	# Note: both default_permissions and atime must be enabled
+	atf_check fuse-ext2 -o default_permissions,allow_other,rw+ ext2.img \
+		$MOUNTPOINT
+
+	atf_check truncate -s 1m $MOUNTPOINT/file
+	create_block -o file=$MOUNTPOINT/file
+
+	# Force fusefs to open the file, and dirty its atime
+	atf_check dd if=/dev/$dev of=/dev/null count=1 status=none
+
+	# Finally, remove the LUN.  Hopefully it won't panic.
+	atf_check -o ignore ctladm remove -b block -l $LUN
+
+	rm lun-create.txt	# So we don't try to remove the LUN twice
+}
+remove_lun_with_atime_cleanup()
+{
+	cleanup
+	umount $PWD/mnt
+}
+
+atf_init_test_cases()
+{
+	atf_add_test_case remove_lun_with_atime
+}