Re: [libvirt] [PATCH 4/6] Remove duplicate entries in lxcBasicMounts array

-----Original Message----- From: libvir-list-bounces(a)redhat.com

On Behalf Of Daniel P. Berrange Sent: Monday, October 07, 2013 9:07 PM To: libvir-list(a)redhat.com Subject: [libvirt] [PATCH 4/6] Remove duplicate entries in lxcBasicMounts

From: "Daniel P. Berrange" <berrange(a)redhat.com&gt; Currently the lxcBasicMounts array has separate entries for most mounts, to reflect that we must do a separate mount operation to make mounts read-only. Remove the duplicate entries and instead set the MS_RDONLY flag against the main entry. Then change lxcContainerMountBasicFS to look for the MS_RDONLY flag, mask it out & do a separate bind mount. Signed-off-by: Daniel P. Berrange <berrange(a)redhat.com&gt; --- src/lxc/lxc_container.c | 44 +++++++++++++++++++++++++++----------------- 1 file changed, 27 insertions(+), 17 deletions(-) diff --git a/src/lxc/lxc_container.c b/src/lxc/lxc_container.c index 1b1c93b..a7f71ef 100644 --- a/src/lxc/lxc_container.c +++ b/src/lxc/lxc_container.c @@ -756,22 +756,12 @@ typedef struct { } virLXCBasicMountInfo; static const virLXCBasicMountInfo lxcBasicMounts[] = { - /* When we want to make a bind mount readonly, for unknown reasons, - * it is currently necessary to bind it once, and then remount the - * bind with the readonly flag. If this is not done, then the

- * mount point in the main OS becomes readonly too which is not what - * we want. Hence some things have two entries here. - */ { "proc", "/proc", "proc", MS_NOSUID|MS_NOEXEC|MS_NODEV }, - { "/proc/sys", "/proc/sys", NULL, MS_BIND }, - { "/proc/sys", "/proc/sys", NULL, MS_BIND|MS_REMOUNT|MS_RDONLY }, - { "sysfs", "/sys", "sysfs", MS_NOSUID|MS_NOEXEC|MS_NODEV }, - { "sysfs", "/sys", "sysfs", MS_BIND|MS_REMOUNT|MS_RDONLY }, - { "securityfs", "/sys/kernel/security", "securityfs", MS_NOSUID|MS_NOEXEC|MS_NODEV }, - { "securityfs", "/sys/kernel/security", "securityfs", MS_BIND|MS_REMOUNT|MS_RDONLY }, + { "/proc/sys", "/proc/sys", NULL, MS_BIND|MS_RDONLY }, + { "sysfs", "/sys", "sysfs", MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_RDONLY }, + { "securityfs", "/sys/kernel/security", "securityfs", MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_RDONLY }, #if WITH_SELINUX - { SELINUX_MOUNT, SELINUX_MOUNT, "selinuxfs", MS_NOSUID|MS_NOEXEC|MS_NODEV }, - { SELINUX_MOUNT, SELINUX_MOUNT, NULL, MS_BIND|MS_REMOUNT|MS_RDONLY }, + { SELINUX_MOUNT, SELINUX_MOUNT, "selinuxfs", MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_RDONLY }, #endif }; @@ -852,6 +842,7 @@ static int lxcContainerMountBasicFS(bool userns_enabled) VIR_DEBUG("Mounting basic filesystems"); for (i = 0; i < ARRAY_CARDINALITY(lxcBasicMounts); i++) { + bool bindOverReadonly; virLXCBasicMountInfo const *mnt = &lxcBasicMounts[i]; VIR_DEBUG("Processing %s -> %s", @@ -878,13 +869,32 @@ static int lxcContainerMountBasicFS(bool userns_enabled) goto cleanup; } + /* + * We can't immediately set the MS_RDONLY flag when mounting filesystems + * because (in at least some kernel versions) this will propagate back + * to the original mount in the host OS, turning it readonly too.

+ * We mount the filesystem in read-write mode initially, and then

a + * separate read-only bind mount on top of that. + */ + bindOverReadonly = !!(mnt->mflags & MS_RDONLY); + VIR_DEBUG("Mount %s on %s type=%s flags=%x", - mnt->src, mnt->dst, mnt->type, mnt->mflags); - if (mount(mnt->src, mnt->dst, mnt->type, mnt->mflags, NULL) < 0)

+ mnt->src, mnt->dst, mnt->type, mnt->mflags & ~MS_RDONLY); + if (mount(mnt->src, mnt->dst, mnt->type, mnt->mflags & ~MS_RDONLY, NULL) < 0) { virReportSystemError(errno, _("Failed to mount %s on %s type %s flags=%x"), mnt->src, mnt->dst, NULLSTR(mnt->type), - mnt->mflags); + mnt->mflags & ~MS_RDONLY); + goto cleanup; + } + + if (bindOverReadonly && + mount(mnt->src, mnt->dst, NULL, + MS_BIND|MS_REMOUNT|MS_RDONLY, NULL) < 0) { + virReportSystemError(errno, + _("Failed to re-mount %s on %s flags=%x"), + mnt->src, mnt->dst, + MS_BIND|MS_REMOUNT|MS_RDONLY); goto cleanup; } } -- 1.8.3.1 -- libvir-list mailing list libvir-list(a)redhat.com https://www.redhat.com/mailman/listinfo/libvir-list