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Merge pull request #3114 from cgwalters/root-ovl
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prepare-root: Add support for root.transient
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ericcurtin authored Dec 8, 2023
2 parents 508b6ea + 8fbaeba commit 071053d
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Showing 6 changed files with 115 additions and 6 deletions.
7 changes: 7 additions & 0 deletions src/libostree/ostree-sysroot-cleanup.c
Original file line number Diff line number Diff line change
Expand Up @@ -218,6 +218,7 @@ gboolean
_ostree_sysroot_rmrf_deployment (OstreeSysroot *self, OstreeDeployment *deployment,
GCancellable *cancellable, GError **error)
{
g_autofree char *backing_relpath = _ostree_sysroot_get_deployment_backing_relpath (deployment);
g_autofree char *origin_relpath = ostree_deployment_get_origin_relpath (deployment);
g_autofree char *deployment_path = ostree_sysroot_get_deployment_dirpath (self, deployment);
struct stat stbuf;
Expand All @@ -238,6 +239,12 @@ _ostree_sysroot_rmrf_deployment (OstreeSysroot *self, OstreeDeployment *deployme
/* This deployment wasn't referenced, so delete it */
if (!_ostree_linuxfs_fd_alter_immutable_flag (deployment_fd, FALSE, cancellable, error))
return FALSE;
/* Note we must delete the origin and backing directories first, as the "source of truth"
* is the deployment path. We don't currently have code that detects "orphaned"
* origin files or work directories.
*/
if (!glnx_shutil_rm_rf_at (self->sysroot_fd, backing_relpath, cancellable, error))
return FALSE;
if (!glnx_shutil_rm_rf_at (self->sysroot_fd, origin_relpath, cancellable, error))
return FALSE;
if (!glnx_shutil_rm_rf_at (self->sysroot_fd, deployment_path, cancellable, error))
Expand Down
50 changes: 50 additions & 0 deletions src/libostree/ostree-sysroot-deploy.c
Original file line number Diff line number Diff line change
Expand Up @@ -3078,6 +3078,10 @@ sysroot_initialize_deployment (OstreeSysroot *self, const char *osname, const ch
if (!require_stateroot (self, osname, error))
return FALSE;

g_autofree char *stateroot_backing = g_strdup_printf ("ostree/deploy/%s/backing", osname);
if (!glnx_shutil_mkdir_p_at (self->sysroot_fd, stateroot_backing, 0700, cancellable, error))
return glnx_prefix_error (error, "Creating backing directory");

OstreeRepo *repo = ostree_sysroot_repo (self);

gint new_deployserial;
Expand Down Expand Up @@ -3295,6 +3299,49 @@ sysroot_finalize_selinux_policy (int deployment_dfd, GError **error)
}
#endif /* HAVE_SELINUX */

static gboolean
sysroot_initialize_deployment_backing (OstreeSysroot *self, OstreeDeployment *deployment,
OstreeSePolicy *sepolicy, GError **error)
{
GLNX_AUTO_PREFIX_ERROR ("Preparing deployment backing dir", error);
g_autofree char *deployment_path = ostree_sysroot_get_deployment_dirpath (self, deployment);
g_autofree char *backing_relpath = _ostree_sysroot_get_deployment_backing_relpath (deployment);
struct stat stbuf;

if (!glnx_fstatat (self->sysroot_fd, deployment_path, &stbuf, AT_SYMLINK_NOFOLLOW, error))
return FALSE;

// Create the "backing" directory with additional data */
if (!glnx_ensure_dir (self->sysroot_fd, backing_relpath, 0700, error))
return glnx_prefix_error (error, "Creating backing dir");

// The root-transient holds overlayfs directories for the root
g_autofree char *rootovldir
= g_build_filename (backing_relpath, OSTREE_DEPLOYMENT_ROOT_TRANSIENT_DIR, NULL);
if (!glnx_ensure_dir (self->sysroot_fd, rootovldir, 0700, error))
return glnx_prefix_error (error, "Creating root ovldir");

// The overlayfs work (subdirectory of root-transient)
g_autofree char *workdir = g_build_filename (rootovldir, "work", NULL);
if (!glnx_ensure_dir (self->sysroot_fd, workdir, 0700, error))
return glnx_prefix_error (error, "Creating work dir");

// Create the overlayfs upper; this needs to have the same mode and SELinux label as the root
{
g_auto (OstreeSepolicyFsCreatecon) con = {
0,
};

if (!_ostree_sepolicy_preparefscreatecon (&con, sepolicy, "/", stbuf.st_mode, error))
return glnx_prefix_error (error, "Looking up SELinux label for /");
g_autofree char *upperdir = g_build_filename (rootovldir, "upper", NULL);
if (!glnx_ensure_dir (self->sysroot_fd, upperdir, stbuf.st_mode, error))
return glnx_prefix_error (error, "Creating upper dir");
}

return TRUE;
}

static gboolean
sysroot_finalize_deployment (OstreeSysroot *self, OstreeDeployment *deployment,
OstreeDeployment *merge_deployment, GCancellable *cancellable,
Expand Down Expand Up @@ -3360,6 +3407,9 @@ sysroot_finalize_deployment (OstreeSysroot *self, OstreeDeployment *deployment,
if (!selinux_relabel_var_if_needed (self, sepolicy, os_deploy_dfd, cancellable, error))
return FALSE;

if (!sysroot_initialize_deployment_backing (self, deployment, sepolicy, error))
return FALSE;

/* Rewrite the origin using the final merged selinux config, just to be
* conservative about getting the right labels.
*/
Expand Down
3 changes: 1 addition & 2 deletions src/libostree/ostree-sysroot-private.h
Original file line number Diff line number Diff line change
Expand Up @@ -142,8 +142,7 @@ gboolean _ostree_sysroot_boot_complete (OstreeSysroot *self, GCancellable *cance

OstreeDeployment *_ostree_sysroot_deserialize_deployment_from_variant (GVariant *v, GError **error);

char *_ostree_sysroot_get_origin_relpath (GFile *path, guint32 *out_device, guint64 *out_inode,
GCancellable *cancellable, GError **error);
char *_ostree_sysroot_get_deployment_backing_relpath (OstreeDeployment *deployment);

gboolean _ostree_sysroot_rmrf_deployment (OstreeSysroot *sysroot, OstreeDeployment *deployment,
GCancellable *cancellable, GError **error);
Expand Down
13 changes: 12 additions & 1 deletion src/libostree/ostree-sysroot.c
Original file line number Diff line number Diff line change
Expand Up @@ -36,7 +36,7 @@
#include "ostree-repo-private.h"
#include "ostree-sepolicy-private.h"
#include "ostree-sysroot-private.h"
#include "ostree.h"
#include "otcore.h"

/**
* SECTION:ostree-sysroot
Expand Down Expand Up @@ -1965,6 +1965,17 @@ ostree_sysroot_simple_write_deployment (OstreeSysroot *sysroot, const char *osna
return TRUE;
}

/* Return the sysroot-relative path to the "backing" directory of a deployment
* which can hold additional data.
*/
char *
_ostree_sysroot_get_deployment_backing_relpath (OstreeDeployment *deployment)
{
return g_strdup_printf (
"ostree/deploy/%s/backing/%s.%d", ostree_deployment_get_osname (deployment),
ostree_deployment_get_csum (deployment), ostree_deployment_get_deployserial (deployment));
}

/* Deploy a copy of @target_deployment */
static gboolean
clone_deployment (OstreeSysroot *sysroot, OstreeDeployment *target_deployment,
Expand Down
7 changes: 7 additions & 0 deletions src/libotcore/otcore.h
Original file line number Diff line number Diff line change
Expand Up @@ -55,6 +55,11 @@ GKeyFile *otcore_load_config (int rootfs, const char *filename, GError **error);
// we make it with mode 0 (which requires CAP_DAC_OVERRIDE to pass through).
#define OTCORE_RUN_OSTREE_PRIVATE "/run/ostree/.private"

// The directory holding extra/backing data for a deployment, such as overlayfs workdirs
#define OSTREE_DEPLOYMENT_BACKING_DIR "backing"
// The directory holding the root overlayfs
#define OSTREE_DEPLOYMENT_ROOT_TRANSIENT_DIR "root-transient"

// The name of the composefs metadata root
#define OSTREE_COMPOSEFS_NAME ".ostree.cfs"
// The temporary directory used for the EROFS mount; it's in the .private directory
Expand All @@ -70,6 +75,8 @@ GKeyFile *otcore_load_config (int rootfs, const char *filename, GError **error);
// This key if present contains the public key successfully used
// to verify the signature.
#define OTCORE_RUN_BOOTED_KEY_COMPOSEFS_SIGNATURE "composefs.signed"
// This key will be present if the root is transient
#define OTCORE_RUN_BOOTED_KEY_ROOT_TRANSIENT "root.transient"
// This key will be present if the sysroot-ro flag was found
#define OTCORE_RUN_BOOTED_KEY_SYSROOT_RO "sysroot-ro"

Expand Down
41 changes: 38 additions & 3 deletions src/switchroot/ostree-prepare-root.c
Original file line number Diff line number Diff line change
Expand Up @@ -87,6 +87,8 @@
#define SYSROOT_KEY "sysroot"
#define READONLY_KEY "readonly"

/* This key configures the / mount in the deployment root */
#define ROOT_KEY "root"
#define ETC_KEY "etc"
#define TRANSIENT_KEY "transient"

Expand Down Expand Up @@ -352,6 +354,11 @@ main (int argc, char *argv[])
errx (EXIT_FAILURE, "Failed to parse config: %s", error->message);

gboolean sysroot_readonly = FALSE;
gboolean root_transient = FALSE;

if (!ot_keyfile_get_boolean_with_default (config, ROOT_KEY, TRANSIENT_KEY, FALSE, &root_transient,
&error))
return FALSE;

// We always parse the composefs config, because we want to detect and error
// out if it's enabled, but not supported at compile time.
Expand All @@ -374,7 +381,12 @@ main (int argc, char *argv[])
const char *root_mountpoint = realpath (root_arg, NULL);
if (root_mountpoint == NULL)
err (EXIT_FAILURE, "realpath(\"%s\")", root_arg);
char *deploy_path = resolve_deploy_path (root_mountpoint);
g_autofree char *deploy_path = resolve_deploy_path (root_mountpoint);
const char *deploy_directory_name = glnx_basename (deploy_path);
// Note that realpath() should have stripped any trailing `/` which shouldn't
// be in the karg to start with, but we assert here to be sure we have a non-empty
// filename.
g_assert (deploy_directory_name && *deploy_directory_name);

if (mkdirat (AT_FDCWD, OTCORE_RUN_OSTREE, 0755) < 0)
err (EXIT_FAILURE, "Failed to create %s", OTCORE_RUN_OSTREE);
Expand Down Expand Up @@ -510,13 +522,36 @@ main (int argc, char *argv[])
errx (EXIT_FAILURE, "composefs: enabled at runtime, but support is not compiled in");
#endif

if (!using_composefs)
if (root_transient)
{
/* if (using_composefs)
* TODO: Add support to libcomposefs to mount writably; for now we end up with two overlayfs
* which is a bit silly.
*/

g_autofree char *backingdir = g_strdup_printf ("../../backing/%s", deploy_directory_name);
g_autofree char *workdir
= g_build_filename (backingdir, OSTREE_DEPLOYMENT_ROOT_TRANSIENT_DIR, "work", NULL);
g_autofree char *upperdir
= g_build_filename (backingdir, OSTREE_DEPLOYMENT_ROOT_TRANSIENT_DIR, "upper", NULL);
g_autofree char *ovl_options
= g_strdup_printf ("lowerdir=.,upperdir=%s,workdir=%s", upperdir, workdir);
if (mount ("overlay", TMP_SYSROOT, "overlay", MS_SILENT, ovl_options) < 0)
err (EXIT_FAILURE, "failed to mount transient root overlayfs");
g_print ("Enabled transient /\n");
}
else if (!using_composefs)
{
g_print ("Using legacy ostree bind mount for /\n");
/* The deploy root starts out bind mounted to sysroot.tmp */
if (mount (deploy_path, TMP_SYSROOT, NULL, MS_BIND | MS_SILENT, NULL) < 0)
err (EXIT_FAILURE, "failed to make initial bind mount %s", deploy_path);
}

/* Pass on the state */
g_variant_builder_add (&metadata_builder, "{sv}", OTCORE_RUN_BOOTED_KEY_ROOT_TRANSIENT,
g_variant_new_boolean (root_transient));

/* This will result in a system with /sysroot read-only. Thus, two additional
* writable bind-mounts (for /etc and /var) are required later on. */
if (sysroot_readonly)
Expand Down Expand Up @@ -548,7 +583,7 @@ main (int argc, char *argv[])
/* Prepare /etc.
* No action required if sysroot is writable. Otherwise, a bind-mount for
* the deployment needs to be created and remounted as read/write. */
if (sysroot_readonly || using_composefs)
if (sysroot_readonly || using_composefs || root_transient)
{
gboolean etc_transient = FALSE;
if (!ot_keyfile_get_boolean_with_default (config, ETC_KEY, TRANSIENT_KEY, FALSE,
Expand Down

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