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

[Wolfgang Bumiller]

looks mostly good, just the ExecStartPre= lines in the service files
should be dropped

On Mon, Mar 25, 2024 at 06:28:28PM +0100, Filip Schauer wrote:
> 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 at proxmox.com>
> ---
>  debian/rules                     | 3 +++
>  src/Makefile                     | 3 +++
>  src/PVE/LXC.pm                   | 2 +-
>  src/pve-container-debug at .service | 1 +
>  src/pve-container-mounthotplug   | 7 +++++++
>  src/pve-container at .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 at .service b/src/pve-container-debug at .service
> index 7cfebaa..cd0895c 100644
> --- a/src/pve-container-debug at .service
> +++ b/src/pve-container-debug at .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

^ This hunk should be dropped. The entry in d/rules is enough, and this
is the wrong place anyway, as this is triggered when starting a new
container, and not when hotplugging.

> 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 at .service b/src/pve-container at .service
> index fdc373e..1437858 100644
> --- a/src/pve-container at .service
> +++ b/src/pve-container at .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

^ same for this one