diff --git a/Makefile-switchroot.am b/Makefile-switchroot.am index 4423fdcd0d..cb9e156ee2 100644 --- a/Makefile-switchroot.am +++ b/Makefile-switchroot.am @@ -55,7 +55,8 @@ ostree_remount_SOURCES = \ src/switchroot/ostree-mount-util.h \ src/switchroot/ostree-remount.c \ $(NULL) -ostree_remount_CPPFLAGS = $(AM_CPPFLAGS) -Isrc/switchroot +ostree_remount_CPPFLAGS = $(AM_CPPFLAGS) $(OT_INTERNAL_GIO_UNIX_CFLAGS) -Isrc/switchroot -I$(srcdir)/libglnx +ostree_remount_LDADD = $(AM_LDFLAGS) $(OT_INTERNAL_GIO_UNIX_LIBS) libglnx.la # This is the "new mode" of using a generator for /var; see # https://github.com/ostreedev/ostree/issues/855 diff --git a/apidoc/ostree-sections.txt b/apidoc/ostree-sections.txt index 5dbafc5fdf..11e131710c 100644 --- a/apidoc/ostree-sections.txt +++ b/apidoc/ostree-sections.txt @@ -495,6 +495,7 @@ ostree_sepolicy_get_type OstreeSysroot ostree_sysroot_new ostree_sysroot_new_default +ostree_sysroot_initialize ostree_sysroot_get_path ostree_sysroot_load ostree_sysroot_load_if_changed @@ -504,6 +505,7 @@ ostree_sysroot_lock_async ostree_sysroot_lock_finish ostree_sysroot_unlock ostree_sysroot_unload +ostree_sysroot_set_mount_namespace_in_use ostree_sysroot_get_fd ostree_sysroot_ensure_initialized ostree_sysroot_get_bootversion diff --git a/src/libostree/libostree-devel.sym b/src/libostree/libostree-devel.sym index 4ff2b86f9d..ab35fbbc70 100644 --- a/src/libostree/libostree-devel.sym +++ b/src/libostree/libostree-devel.sym @@ -19,6 +19,8 @@ /* Add new symbols here. Release commits should copy this section into -released.sym. */ LIBOSTREE_2018.10 { + ostree_sysroot_initialize; + ostree_sysroot_set_mount_namespace_in_use; } LIBOSTREE_2018.9; /* Stub section for the stable release *after* this development one; don't diff --git a/src/libostree/ostree-sysroot-cleanup.c b/src/libostree/ostree-sysroot-cleanup.c index 7a352e6b4b..048a5ca93b 100644 --- a/src/libostree/ostree-sysroot-cleanup.c +++ b/src/libostree/ostree-sysroot-cleanup.c @@ -454,6 +454,9 @@ ostree_sysroot_cleanup_prune_repo (OstreeSysroot *sysroot, OstreeRepo *repo = ostree_sysroot_repo (sysroot); const guint depth = 0; /* Historical default */ + if (!_ostree_sysroot_ensure_writable (sysroot, error)) + return FALSE; + /* Hold an exclusive lock by default across gathering refs and doing * the prune. */ @@ -534,7 +537,10 @@ _ostree_sysroot_cleanup_internal (OstreeSysroot *self, GError **error) { g_return_val_if_fail (OSTREE_IS_SYSROOT (self), FALSE); - g_return_val_if_fail (self->loaded, FALSE); + g_return_val_if_fail (self->loadstate == OSTREE_SYSROOT_LOAD_STATE_LOADED, FALSE); + + if (!_ostree_sysroot_ensure_writable (self, error)) + return FALSE; if (!cleanup_other_bootversions (self, cancellable, error)) return glnx_prefix_error (error, "Cleaning bootversions"); diff --git a/src/libostree/ostree-sysroot-deploy.c b/src/libostree/ostree-sysroot-deploy.c index d37861b7ba..0756cc62af 100644 --- a/src/libostree/ostree-sysroot-deploy.c +++ b/src/libostree/ostree-sysroot-deploy.c @@ -55,6 +55,9 @@ #define OSTREE_DEPLOYMENT_FINALIZING_ID SD_ID128_MAKE(e8,64,6c,d6,3d,ff,46,25,b7,79,09,a8,e7,a4,09,94) #endif +static gboolean +is_ro_mount (const char *path); + /* * Like symlinkat() but overwrites (atomically) an existing * symlink. @@ -810,6 +813,9 @@ write_origin_file_internal (OstreeSysroot *sysroot, GCancellable *cancellable, GError **error) { + if (!_ostree_sysroot_ensure_writable (sysroot, error)) + return FALSE; + GLNX_AUTO_PREFIX_ERROR ("Writing out origin file", error); GKeyFile *origin = new_origin ? new_origin : ostree_deployment_get_origin (deployment); @@ -2181,7 +2187,10 @@ ostree_sysroot_write_deployments_with_options (OstreeSysroot *self, GCancellable *cancellable, GError **error) { - g_assert (self->loaded); + g_assert (self->loadstate == OSTREE_SYSROOT_LOAD_STATE_LOADED); + + if (!_ostree_sysroot_ensure_writable (self, error)) + return FALSE; /* Dealing with the staged deployment is quite tricky here. This function is * primarily concerned with writing out "finalized" deployments which have @@ -2338,7 +2347,6 @@ ostree_sysroot_write_deployments_with_options (OstreeSysroot *self, if (boot_was_ro_mount) { - /* TODO: Use new mount namespace. https://github.com/ostreedev/ostree/issues/1265 */ if (mount ("/boot", "/boot", NULL, MS_REMOUNT | MS_SILENT, NULL) < 0) return glnx_throw_errno_prefix (error, "Remounting /boot read-write"); } @@ -2364,8 +2372,10 @@ ostree_sysroot_write_deployments_with_options (OstreeSysroot *self, /* Note equivalent of try/finally here */ gboolean success = write_deployments_bootswap (self, new_deployments, opts, bootloader, &syncstats, cancellable, error); - /* Below here don't set GError until the if (!success) check */ - if (boot_was_ro_mount) + /* Below here don't set GError until the if (!success) check. + * Note we only bother remounting if a mount namespace isn't in use. + * */ + if (boot_was_ro_mount && !self->mount_namespace_in_use) { if (mount ("/boot", "/boot", NULL, MS_REMOUNT | MS_RDONLY | MS_SILENT, NULL) < 0) { @@ -2674,6 +2684,9 @@ ostree_sysroot_deploy_tree (OstreeSysroot *self, GCancellable *cancellable, GError **error) { + if (!_ostree_sysroot_ensure_writable (self, error)) + return FALSE; + g_autoptr(OstreeDeployment) deployment = NULL; if (!sysroot_initialize_deployment (self, osname, revision, origin, override_kernel_argv, &deployment, cancellable, error)) @@ -2773,6 +2786,9 @@ ostree_sysroot_stage_tree (OstreeSysroot *self, GCancellable *cancellable, GError **error) { + if (!_ostree_sysroot_ensure_writable (self, error)) + return FALSE; + OstreeDeployment *booted_deployment = ostree_sysroot_get_booted_deployment (self); if (booted_deployment == NULL) return glnx_throw (error, "Cannot stage a deployment when not currently booted into an OSTree system"); @@ -2987,6 +3003,9 @@ ostree_sysroot_deployment_set_kargs (OstreeSysroot *self, GCancellable *cancellable, GError **error) { + if (!_ostree_sysroot_ensure_writable (self, error)) + return FALSE; + /* For now; instead of this do a redeployment */ g_assert (!ostree_deployment_is_staged (deployment)); @@ -3034,6 +3053,8 @@ ostree_sysroot_deployment_set_mutable (OstreeSysroot *self, GCancellable *cancellable, GError **error) { + if (!_ostree_sysroot_ensure_writable (self, error)) + return FALSE; if (g_cancellable_set_error_if_cancelled (cancellable, error)) return FALSE; diff --git a/src/libostree/ostree-sysroot-private.h b/src/libostree/ostree-sysroot-private.h index 9da6d4c9e1..fd33a9e176 100644 --- a/src/libostree/ostree-sysroot-private.h +++ b/src/libostree/ostree-sysroot-private.h @@ -41,6 +41,12 @@ typedef enum { OSTREE_SYSROOT_DEBUG_TEST_STAGED_PATH = 1 << 3, } OstreeSysrootDebugFlags; +typedef enum { + OSTREE_SYSROOT_LOAD_STATE_NONE, + OSTREE_SYSROOT_LOAD_STATE_INIT, + OSTREE_SYSROOT_LOAD_STATE_LOADED, +} OstreeSysrootLoadState; + /** * OstreeSysroot: * Internal struct @@ -52,7 +58,8 @@ struct OstreeSysroot { int sysroot_fd; GLnxLockFile lock; - gboolean loaded; + OstreeSysrootLoadState loadstate; + gboolean mount_namespace_in_use; /* TRUE if caller has told us they used CLONE_NEWNS */ gboolean root_is_ostree_booted; /* TRUE if sysroot is / and we are booted via ostree */ /* The device/inode for /, used to detect booted deployment */ dev_t root_device; @@ -79,6 +86,10 @@ struct OstreeSysroot { #define _OSTREE_SYSROOT_DEPLOYMENT_RUNSTATE_DIR "/run/ostree/deployment-state/" #define _OSTREE_SYSROOT_DEPLOYMENT_RUNSTATE_FLAG_DEVELOPMENT "unlocked-development" +gboolean +_ostree_sysroot_ensure_writable (OstreeSysroot *self, + GError **error); + void _ostree_sysroot_emit_journal_msg (OstreeSysroot *self, const char *msg); diff --git a/src/libostree/ostree-sysroot.c b/src/libostree/ostree-sysroot.c index 84c1230147..6221850cbd 100644 --- a/src/libostree/ostree-sysroot.c +++ b/src/libostree/ostree-sysroot.c @@ -226,6 +226,33 @@ ostree_sysroot_new_default (void) return ostree_sysroot_new (NULL); } +/** + * ostree_sysroot_set_mount_namespace_in_use: + * + * If this function is invoked, then libostree will assume that + * a private Linux mount namespace has been created by the process. + * The primary use case for this is to have e.g. /sysroot mounted + * read-only by default. + * + * If this function has been called, then when a function which requires + * writable access is invoked, libostree will automatically remount as writable + * any mount points on which it operates. This currently is just `/sysroot` and + * `/boot`. + * + * If you invoke this function, it must be before ostree_sysroot_load(); it may + * be invoked before or after ostree_sysroot_initialize(). + * + * Since: 2018.10 + */ +void +ostree_sysroot_set_mount_namespace_in_use (OstreeSysroot *self) +{ + /* Must be before we're loaded, as otherwise we'd have to close/reopen all our + fds, e.g. the repo */ + g_return_if_fail (self->loadstate < OSTREE_SYSROOT_LOAD_STATE_LOADED); + self->mount_namespace_in_use = TRUE; +} + /** * ostree_sysroot_get_path: * @self: @@ -238,6 +265,7 @@ ostree_sysroot_get_path (OstreeSysroot *self) return self->path; } +/* Open a directory file descriptor for the sysroot if we haven't yet */ static gboolean ensure_sysroot_fd (OstreeSysroot *self, GError **error) @@ -251,13 +279,55 @@ ensure_sysroot_fd (OstreeSysroot *self, return TRUE; } +/* Remount /sysroot read-write if necessary */ +gboolean +_ostree_sysroot_ensure_writable (OstreeSysroot *self, + GError **error) +{ + /* Do nothing if no mount namespace is in use */ + if (!self->mount_namespace_in_use) + return TRUE; + + /* If a mount namespace is in use, ensure we're initialized */ + if (!ostree_sysroot_initialize (self, error)) + return FALSE; + + /* If we aren't operating on a booted system, then we don't + * do anything with mounts. Also, if the caller hasn't + * explicitly told us they made a mount namespace, we don't + * do any remounts. + */ + if (!self->root_is_ostree_booted) + return TRUE; + + /* Check if /sysroot is a read-only mountpoint */ + struct statvfs stvfsbuf; + if (statvfs ("/sysroot", &stvfsbuf) < 0) + return glnx_throw_errno_prefix (error, "fstatvfs(/sysroot)"); + if ((stvfsbuf.f_flag & ST_RDONLY) == 0) + return TRUE; + + /* OK, let's remount writable. */ + if (mount ("/sysroot", "/sysroot", NULL, MS_REMOUNT | MS_RELATIME, "") < 0) + return glnx_throw_errno_prefix (error, "Remounting /sysroot read-write"); + + /* Reopen our fd */ + glnx_close_fd (&self->sysroot_fd); + if (!ensure_sysroot_fd (self, error)) + return FALSE; + /* But we can't have opened the repo yet */ + g_assert (self->repo == NULL); + + return TRUE; +} + /** * ostree_sysroot_get_fd: * @self: Sysroot * - * Access a file descriptor that refers to the root directory of this - * sysroot. ostree_sysroot_load() must have been invoked prior to - * calling this function. + * Access a file descriptor that refers to the root directory of this sysroot. + * ostree_sysroot_initialize() (or ostree_sysroot_load()) must have been invoked + * prior to calling this function. * * Returns: A file descriptor valid for the lifetime of @self */ @@ -798,6 +868,58 @@ ensure_repo (OstreeSysroot *self, return TRUE; } +/** + * ostree_sysroot_initialize: + * @self: sysroot + * + * Subset of ostree_sysroot_load(); performs basic initialization. Notably, one + * can invoke `ostree_sysroot_get_fd()` after calling this function. + * + * It is not necessary to call this function if ostree_sysroot_load() is + * invoked. + * + * Since: 2018.10 + */ +gboolean +ostree_sysroot_initialize (OstreeSysroot *self, + GError **error) +{ + + if (self->loadstate < OSTREE_SYSROOT_LOAD_STATE_INIT) + { + /* Gather some global state; first if we have the global ostree-booted flag; + * we'll use it to sanity check that we found a booted deployment for example. + * Second, we also find out whether sysroot == /. + */ + if (!glnx_fstatat_allow_noent (AT_FDCWD, "/run/ostree-booted", NULL, 0, error)) + return FALSE; + const gboolean ostree_booted = (errno == 0); + + { struct stat root_stbuf; + if (!glnx_fstatat (AT_FDCWD, "/", &root_stbuf, 0, error)) + return FALSE; + self->root_device = root_stbuf.st_dev; + self->root_inode = root_stbuf.st_ino; + } + + struct stat self_stbuf; + if (!glnx_fstatat (AT_FDCWD, gs_file_get_path_cached (self->path), &self_stbuf, 0, error)) + return FALSE; + + const gboolean root_is_sysroot = + (self->root_device == self_stbuf.st_dev && + self->root_inode == self_stbuf.st_ino); + + self->root_is_ostree_booted = (ostree_booted && root_is_sysroot); + self->loadstate = OSTREE_SYSROOT_LOAD_STATE_INIT; + } + + if (!ensure_sysroot_fd (self, error)) + return FALSE; + + return TRUE; +} + /* Reload the staged deployment from the file in /run */ gboolean _ostree_sysroot_reload_staged (OstreeSysroot *self, @@ -861,7 +983,7 @@ ostree_sysroot_load_if_changed (OstreeSysroot *self, GCancellable *cancellable, GError **error) { - if (!ensure_sysroot_fd (self, error)) + if (!ostree_sysroot_initialize (self, error)) return FALSE; /* Here we also lazily initialize the repository. We didn't do this @@ -871,34 +993,6 @@ ostree_sysroot_load_if_changed (OstreeSysroot *self, if (!ensure_repo (self, error)) return FALSE; - /* Gather some global state; first if we have the global ostree-booted flag; - * we'll use it to sanity check that we found a booted deployment for example. - * Second, we also find out whether sysroot == /. - */ - if (!self->loaded) - { - if (!glnx_fstatat_allow_noent (AT_FDCWD, "/run/ostree-booted", NULL, 0, error)) - return FALSE; - const gboolean ostree_booted = (errno == 0); - - { struct stat root_stbuf; - if (!glnx_fstatat (AT_FDCWD, "/", &root_stbuf, 0, error)) - return FALSE; - self->root_device = root_stbuf.st_dev; - self->root_inode = root_stbuf.st_ino; - } - - struct stat self_stbuf; - if (!glnx_fstat (self->sysroot_fd, &self_stbuf, error)) - return FALSE; - - const gboolean root_is_sysroot = - (self->root_device == self_stbuf.st_dev && - self->root_inode == self_stbuf.st_ino); - - self->root_is_ostree_booted = (ostree_booted && root_is_sysroot); - } - int bootversion = 0; if (!read_current_bootversion (self, &bootversion, cancellable, error)) return FALSE; @@ -969,8 +1063,8 @@ ostree_sysroot_load_if_changed (OstreeSysroot *self, ostree_deployment_set_index (deployment, i); } - /* Determine whether we're "physical" or not, the first time we initialize */ - if (!self->loaded) + /* Determine whether we're "physical" or not, the first time we load deployments */ + if (self->loadstate < OSTREE_SYSROOT_LOAD_STATE_LOADED) { /* If we have a booted deployment, the sysroot is / and we're definitely * not physical. @@ -988,13 +1082,14 @@ ostree_sysroot_load_if_changed (OstreeSysroot *self, self->is_physical = TRUE; } /* Otherwise, the default is FALSE */ + + self->loadstate = OSTREE_SYSROOT_LOAD_STATE_LOADED; } self->bootversion = bootversion; self->subbootversion = subbootversion; self->deployments = deployments; deployments = NULL; /* Transfer ownership */ - self->loaded = TRUE; self->loaded_ts = stbuf.st_mtim; if (out_changed) @@ -1023,7 +1118,7 @@ ostree_sysroot_get_subbootversion (OstreeSysroot *self) OstreeDeployment * ostree_sysroot_get_booted_deployment (OstreeSysroot *self) { - g_return_val_if_fail (self->loaded, NULL); + g_return_val_if_fail (self->loadstate == OSTREE_SYSROOT_LOAD_STATE_LOADED, NULL); return self->booted_deployment; } @@ -1037,7 +1132,7 @@ ostree_sysroot_get_booted_deployment (OstreeSysroot *self) OstreeDeployment * ostree_sysroot_get_staged_deployment (OstreeSysroot *self) { - g_return_val_if_fail (self->loaded, NULL); + g_return_val_if_fail (self->loadstate == OSTREE_SYSROOT_LOAD_STATE_LOADED, NULL); return self->staged_deployment; } @@ -1051,7 +1146,7 @@ ostree_sysroot_get_staged_deployment (OstreeSysroot *self) GPtrArray * ostree_sysroot_get_deployments (OstreeSysroot *self) { - g_return_val_if_fail (self->loaded, NULL); + g_return_val_if_fail (self->loadstate == OSTREE_SYSROOT_LOAD_STATE_LOADED, NULL); GPtrArray *copy = g_ptr_array_new_with_free_func ((GDestroyNotify)g_object_unref); for (guint i = 0; i < self->deployments->len; i++) @@ -1140,15 +1235,15 @@ ostree_sysroot_get_repo (OstreeSysroot *self, * @self: Sysroot * * This function is a variant of ostree_sysroot_get_repo() that cannot fail, and - * returns a cached repository. Can only be called after ostree_sysroot_load() - * has been invoked successfully. + * returns a cached repository. Can only be called after ostree_sysroot_initialize() + * or ostree_sysroot_load() has been invoked successfully. * * Returns: (transfer none): The OSTree repository in sysroot @self. */ OstreeRepo * ostree_sysroot_repo (OstreeSysroot *self) { - g_return_val_if_fail (self->loaded, NULL); + g_return_val_if_fail (self->loadstate >= OSTREE_SYSROOT_LOAD_STATE_INIT, NULL); g_assert (self->repo); return self->repo; } @@ -1343,6 +1438,10 @@ ostree_sysroot_lock (OstreeSysroot *self, { if (!ensure_sysroot_fd (self, error)) return FALSE; + + if (!_ostree_sysroot_ensure_writable (self, error)) + return FALSE; + return glnx_make_lock_file (self->sysroot_fd, OSTREE_SYSROOT_LOCKFILE, LOCK_EX, &self->lock, error); } @@ -1366,12 +1465,14 @@ ostree_sysroot_try_lock (OstreeSysroot *self, gboolean *out_acquired, GError **error) { - g_autoptr(GError) local_error = NULL; - if (!ensure_sysroot_fd (self, error)) return FALSE; + if (!_ostree_sysroot_ensure_writable (self, error)) + return FALSE; + /* Note use of LOCK_NB */ + g_autoptr(GError) local_error = NULL; if (!glnx_make_lock_file (self->sysroot_fd, OSTREE_SYSROOT_LOCKFILE, LOCK_EX | LOCK_NB, &self->lock, &local_error)) { @@ -1482,7 +1583,7 @@ ostree_sysroot_init_osname (OstreeSysroot *self, GCancellable *cancellable, GError **error) { - if (!ensure_sysroot_fd (self, error)) + if (!_ostree_sysroot_ensure_writable (self, error)) return FALSE; const char *deploydir = glnx_strjoina ("ostree/deploy/", osname); diff --git a/src/libostree/ostree-sysroot.h b/src/libostree/ostree-sysroot.h index 502cd75020..4dd33a6ebc 100644 --- a/src/libostree/ostree-sysroot.h +++ b/src/libostree/ostree-sysroot.h @@ -41,12 +41,19 @@ OstreeSysroot* ostree_sysroot_new (GFile *path); _OSTREE_PUBLIC OstreeSysroot* ostree_sysroot_new_default (void); +_OSTREE_PUBLIC +void ostree_sysroot_set_mount_namespace_in_use (OstreeSysroot *self); + _OSTREE_PUBLIC GFile *ostree_sysroot_get_path (OstreeSysroot *self); _OSTREE_PUBLIC int ostree_sysroot_get_fd (OstreeSysroot *self); +_OSTREE_PUBLIC +gboolean ostree_sysroot_initialize (OstreeSysroot *self, + GError **error); + _OSTREE_PUBLIC gboolean ostree_sysroot_load (OstreeSysroot *self, GCancellable *cancellable, @@ -90,6 +97,10 @@ GFile * ostree_sysroot_get_deployment_origin_path (GFile *deployment_path); _OSTREE_PUBLIC gboolean ostree_sysroot_lock (OstreeSysroot *self, GError **error); + +_OSTREE_PUBLIC +gboolean ostree_sysroot_lock_with_mount_namespace (OstreeSysroot *self, GError **error); + _OSTREE_PUBLIC gboolean ostree_sysroot_try_lock (OstreeSysroot *self, gboolean *out_acquired, diff --git a/src/ostree/ot-main.c b/src/ostree/ot-main.c index a1449aef25..30f6694341 100644 --- a/src/ostree/ot-main.c +++ b/src/ostree/ot-main.c @@ -27,6 +27,7 @@ #include #include +#include #include "ot-main.h" #include "ostree.h" @@ -423,10 +424,42 @@ ostree_admin_option_context_parse (GOptionContext *context, sysroot_path = g_file_new_for_path (opt_sysroot); g_autoptr(OstreeSysroot) sysroot = ostree_sysroot_new (sysroot_path); + if (!ostree_sysroot_initialize (sysroot, error)) + return FALSE; g_signal_connect (sysroot, "journal-msg", G_CALLBACK (on_sysroot_journal_msg), NULL); if ((flags & OSTREE_ADMIN_BUILTIN_FLAG_UNLOCKED) == 0) { + /* If we're requested to lock the sysroot, first find out if the /sysroot + * subdir is a read-only mount point, and if so, create a new mount + * namespace and tell the sysroot that we've done so. See the docs for + * ostree_sysroot_set_mount_namespace_in_use(). + * + * This is a conservative approch; we could just always + * unshare() too. + */ + int sysroot_fd = ostree_sysroot_get_fd (sysroot); + g_assert_cmpint (sysroot_fd, !=, -1); + + glnx_autofd int sysroot_subdir_fd = glnx_opendirat_with_errno (sysroot_fd, "sysroot", TRUE); + if (sysroot_subdir_fd < 0) + { + if (errno != ENOENT) + return glnx_throw_errno_prefix (error, "opendirat"); + } + else if (getuid () == 0) + { + struct statvfs stvfs; + if (fstatvfs (sysroot_subdir_fd, &stvfs) < 0) + return glnx_throw_errno_prefix (error, "fstatvfs"); + if (stvfs.f_flag & ST_RDONLY) + { + if (unshare (CLONE_NEWNS) < 0) + return glnx_throw_errno_prefix (error, "preparing writable sysroot: unshare (CLONE_NEWNS)"); + ostree_sysroot_set_mount_namespace_in_use (sysroot); + } + } + /* Released when sysroot is finalized, or on process exit */ if (!ot_admin_sysroot_lock (sysroot, error)) return FALSE; diff --git a/src/switchroot/ostree-remount.c b/src/switchroot/ostree-remount.c index 5e6d23d3ae..4b4f53561e 100644 --- a/src/switchroot/ostree-remount.c +++ b/src/switchroot/ostree-remount.c @@ -26,6 +26,7 @@ #include #include #include +#include #include #include #include @@ -37,10 +38,14 @@ #include #include +#include + #include "ostree-mount-util.h" +#include "glnx-backport-autocleanups.h" static void -do_remount (const char *target) +do_remount (const char *target, + bool writable) { struct stat stbuf; if (lstat (target, &stbuf) < 0) @@ -54,20 +59,33 @@ do_remount (const char *target) struct statvfs stvfsbuf; if (statvfs (target, &stvfsbuf) == -1) return; - /* If no read-only flag, skip it */ - if ((stvfsbuf.f_flag & ST_RDONLY) == 0) + + const bool currently_writable = ((stvfsbuf.f_flag & ST_RDONLY) == 0); + if (writable == currently_writable) return; - /* It's a mounted, read-only fs; remount it */ - if (mount (target, target, NULL, MS_REMOUNT | MS_SILENT, NULL) < 0) - { - /* Also ignore EINVAL - if the target isn't a mountpoint - * already, then assume things are OK. - */ - if (errno != EINVAL) - err (EXIT_FAILURE, "failed to remount %s", target); - } - else - printf ("Remounted: %s\n", target); + + int mnt_flags = MS_REMOUNT | MS_SILENT; + if (!writable) + mnt_flags |= MS_RDONLY; + if (mount (target, target, NULL, mnt_flags, NULL) < 0) + err (EXIT_FAILURE, "failed to remount %s", target); + + printf ("Remounted %s: %s\n", writable ? "rw" : "ro", target); +} + +static bool +sysroot_is_configured_ro (void) +{ + struct stat stbuf; + static const char config_path[] = "/ostree/repo/config"; + if (stat (config_path, &stbuf) != 0) + return false; + + g_autoptr(GKeyFile) keyfile = g_key_file_new (); + if (!g_key_file_load_from_file (keyfile, config_path, 0, NULL)) + return false; + + return g_key_file_get_boolean (keyfile, "sysroot", "readonly", NULL); } int @@ -95,8 +113,55 @@ main(int argc, char *argv[]) exit (EXIT_SUCCESS); } - do_remount ("/sysroot"); - do_remount ("/var"); + do_remount ("/var", true); + + /* We could also parse the ostree repo config, but...this service + * so far doesn't link to libostree or even glib. + */ + const bool sysroot_readonly = sysroot_is_configured_ro (); + if (!sysroot_readonly) + do_remount ("/sysroot", !sysroot_readonly); + else + { + /* Since /sysroot is the real physical root, we can't simply remount it + * read-only here, as that'd affect e.g. /etc in and also /var if it's not + * a separate mount. Instead, we make new read-only bind mount to it, + * unmount the original, then move the bind mount to /sysroot. + */ + static const char tmp_sysroot[] = "/etc/ostree-sysroot.tmp"; + static const char sysroot[] = "/sysroot"; + + /* This temporary lives in /etc since it needs to be on the same mount. */ + if (mkdir (tmp_sysroot, 0755) < 0) + err (EXIT_FAILURE, "mkdir(%s)", tmp_sysroot); + /* Make it a read-only bind mount to /sysroot */ + if (mount (sysroot, tmp_sysroot, NULL, MS_BIND | MS_PRIVATE, NULL) < 0) + err (EXIT_FAILURE, "failed to bind mount %s %s", sysroot, tmp_sysroot); + if (mount (tmp_sysroot, tmp_sysroot, NULL, MS_BIND | MS_RDONLY | MS_REMOUNT, NULL) < 0) + err (EXIT_FAILURE, "failed to remount ro %s", tmp_sysroot); + if (umount (sysroot) < 0) + err (EXIT_FAILURE, "while remounting %s read-only: umount", sysroot); + + /* HACK: We can't move a mount that's under a shared namespace. So we + * briefly make the sysroot private so that we can move the mount. This + * does introduce a race condition where if e.g. another process mounted + * something in / it wouldn't be visible in other mount namespaces. But + * we're running quite early, before e.g. any container runtimes should + * be starting. + */ + if (mount ("none", "/", NULL, MS_PRIVATE, NULL) < 0) + err (EXIT_FAILURE, "making / private temporarily"); + /* Do the move */ + if (mount (tmp_sysroot, sysroot, NULL, MS_MOVE, NULL) < 0) + err (EXIT_FAILURE, "failed to move read-only %s mount", sysroot); + /* Make / shared again */ + if (mount ("none", "/", NULL, MS_SHARED, NULL) < 0) + err (EXIT_FAILURE, "making / shared again"); + + /* And clean up */ + if (rmdir (tmp_sysroot) < 0) + err (EXIT_FAILURE, "rmdir(%s)", tmp_sysroot); + } exit (EXIT_SUCCESS); }