[pve-devel] [PATCH v2 container 1/2] fix #5160: fix move_mount regression for mount point hotplug

[Filip Schauer <f.schauer@proxmox.com>]

Set up an Apparmor profile to allow moving mounts for mount point
hotplug.

This fixes a regression caused by
kernel commit 157a3537d6 ("apparmor: Fix regression in mount mediation")

The commit introduced move_mount mediation, which now requires
move_mount to be allowed in the Apparmor profile. Although it is allowed
for most paths in the /usr/bin/lxc-start profile, move_mount is called
with a file descriptor instead of a path in mountpoint_insert_staged,
thus it is not affected by the allow rules in
/etc/apparmor.d/abstractions/lxc/container-base.

To fix this, introduce a new Apparmor profile to allow move_mount on
every mount, specifically for mount point hotplug.

Signed-off-by: Filip Schauer <f.schauer@proxmox.com>
---
 debian/rules                     | 3 +++
 src/Makefile                     | 3 +++
 src/PVE/LXC.pm                   | 2 +-
 src/pve-container-debug@.service | 1 +
 src/pve-container-mounthotplug   | 7 +++++++
 src/pve-container@.service       | 1 +
 6 files changed, 16 insertions(+), 1 deletion(-)
 create mode 100644 src/pve-container-mounthotplug

diff --git a/debian/rules b/debian/rules
index d999152..f7edccf 100755
--- a/debian/rules
+++ b/debian/rules
@@ -14,3 +14,6 @@
 
 override_dh_installsystemd:
 	dh_installsystemd -ppve-container --no-start --no-enable --no-restart-after-upgrade -r 'system-pve\x2dcontainer.slice'
+
+override_dh_install:
+	dh_apparmor -p pve-container --profile-name=pve-container-mounthotplug
diff --git a/src/Makefile b/src/Makefile
index 5a7a82e..e0b7734 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -4,6 +4,7 @@ PREFIX=${DESTDIR}/usr
 BINDIR=${PREFIX}/bin
 LIBDIR=${PREFIX}/lib
 SBINDIR=${PREFIX}/sbin
+ETCDIR=${DESTDIR}/etc
 MANDIR=${PREFIX}/share/man
 DOCDIR=${PREFIX}/share/doc/${PACKAGE}
 LXC_SCRIPT_DIR=${PREFIX}/share/lxc
@@ -13,6 +14,7 @@ LXC_CONFIG_DIR=${LXC_SCRIPT_DIR}/config
 LXC_COMMON_CONFIG_DIR=${LXC_CONFIG_DIR}/common.conf.d
 LXC_USERNS_CONFIG_DIR=${LXC_CONFIG_DIR}/userns.conf.d
 SERVICEDIR=${DESTDIR}/lib/systemd/system
+APPARMORDDIR=${ETCDIR}/apparmor.d
 PODDIR=${DOCDIR}/pod
 MAN1DIR=${MANDIR}/man1/
 MAN5DIR=${MANDIR}/man5/
@@ -73,6 +75,7 @@ install: pct lxc-pve.conf pct.1 pct.conf.5 pct.bash-completion pct.zsh-completio
 	gzip -9 ${MAN5DIR}/pct.conf.5
 	cd ${MAN5DIR}; ln -s pct.conf.5.gz ct.conf.5.gz
 	install -D -m 0644 10-pve-ct-inotify-limits.conf ${LIBDIR}/sysctl.d/10-pve-ct-inotify-limits.conf
+	install -D -m 0644 pve-container-mounthotplug ${APPARMORDDIR}/pve-container-mounthotplug
 
 pve-userns.seccomp: /usr/share/lxc/config/common.seccomp
 	cp $< $@
diff --git a/src/PVE/LXC.pm b/src/PVE/LXC.pm
index 7883cfb..7db4833 100644
--- a/src/PVE/LXC.pm
+++ b/src/PVE/LXC.pm
@@ -1974,7 +1974,7 @@ sub mountpoint_hotplug :prototype($$$$$) {
 	my $dir = get_staging_mount_path($opt);
 
 	# Now switch our apparmor profile before mounting:
-	my $data = 'changeprofile /usr/bin/lxc-start';
+	my $data = 'changeprofile pve-container-mounthotplug';
 	if (syswrite($aa_fd, $data, length($data)) != length($data)) {
 	    die "failed to change apparmor profile: $!\n";
 	}
diff --git a/src/pve-container-debug@.service b/src/pve-container-debug@.service
index 7cfebaa..cd0895c 100644
--- a/src/pve-container-debug@.service
+++ b/src/pve-container-debug@.service
@@ -13,6 +13,7 @@ Type=simple
 Delegate=yes
 KillMode=mixed
 TimeoutStopSec=120s
+ExecStartPre=/lib/apparmor/profile-load pve-container-mounthotplug
 ExecStart=/usr/bin/lxc-start -F -n %i -o /dev/stderr -l DEBUG
 ExecStop=/usr/share/lxc/pve-container-stop-wrapper %i
 # Environment=BOOTUP=serial
diff --git a/src/pve-container-mounthotplug b/src/pve-container-mounthotplug
new file mode 100644
index 0000000..e6f3903
--- /dev/null
+++ b/src/pve-container-mounthotplug
@@ -0,0 +1,7 @@
+#include <tunables/global>
+
+profile pve-container-mounthotplug flags=(attach_disconnected) {
+  #include <abstractions/lxc/start-container>
+
+  mount options=(move),
+}
diff --git a/src/pve-container@.service b/src/pve-container@.service
index fdc373e..1437858 100644
--- a/src/pve-container@.service
+++ b/src/pve-container@.service
@@ -13,6 +13,7 @@ Type=simple
 Delegate=yes
 KillMode=mixed
 TimeoutStopSec=120s
+ExecStartPre=/lib/apparmor/profile-load pve-container-mounthotplug
 ExecStart=/usr/bin/lxc-start -F -n %i
 ExecStop=/usr/share/lxc/pve-container-stop-wrapper %i
 # Environment=BOOTUP=serial
-- 
2.39.2