dissect-image: support images without rootfs but with /usr/
Let's add support for images that include an /usr/ file system but no root fs. Mount a tmpfs as root for images like this, all controlled by a new flag DISSECT_IMAGE_USR_NO_ROOT. This is useful for entirely stateless images, that come up pristine on every single boot.
This commit is contained in:
Lennart Poettering
+116
-58
@@ -1100,64 +1100,85 @@ int dissect_image(
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m->partitions[PARTITION_ROOT_SECONDARY_VERITY].found = false;
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m->partitions[PARTITION_USR_SECONDARY].found = false;
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m->partitions[PARTITION_USR_SECONDARY_VERITY].found = false;
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} else {
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/* No root partition found? Then let's see if ther's one for the secondary architecture. And if not
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* either, then check if there's a single generic one, and use that. */
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if (m->partitions[PARTITION_ROOT_VERITY].found)
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} else if (m->partitions[PARTITION_ROOT_VERITY].found)
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return -EADDRNOTAVAIL; /* Verity found but no matching rootfs? Something is off, refuse. */
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else if (m->partitions[PARTITION_ROOT_SECONDARY].found) {
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/* No root partition found but there's one for the secondary architecture? Then upgrade
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* secondary arch to first */
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m->partitions[PARTITION_ROOT] = m->partitions[PARTITION_ROOT_SECONDARY];
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zero(m->partitions[PARTITION_ROOT_SECONDARY]);
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m->partitions[PARTITION_ROOT_VERITY] = m->partitions[PARTITION_ROOT_SECONDARY_VERITY];
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zero(m->partitions[PARTITION_ROOT_SECONDARY_VERITY]);
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m->partitions[PARTITION_USR] = m->partitions[PARTITION_USR_SECONDARY];
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zero(m->partitions[PARTITION_USR_SECONDARY]);
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m->partitions[PARTITION_USR_VERITY] = m->partitions[PARTITION_USR_SECONDARY_VERITY];
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zero(m->partitions[PARTITION_USR_SECONDARY_VERITY]);
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} else if (m->partitions[PARTITION_ROOT_SECONDARY_VERITY].found)
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return -EADDRNOTAVAIL; /* as above */
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else if (m->partitions[PARTITION_USR].found) {
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/* Invalidate secondary arch /usr/ if we found the primary arch */
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m->partitions[PARTITION_USR_SECONDARY].found = false;
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m->partitions[PARTITION_USR_SECONDARY_VERITY].found = false;
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} else if (m->partitions[PARTITION_USR_VERITY].found)
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return -EADDRNOTAVAIL; /* as above */
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else if (m->partitions[PARTITION_USR_SECONDARY].found) {
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/* Upgrade secondary arch to primary */
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m->partitions[PARTITION_USR] = m->partitions[PARTITION_USR_SECONDARY];
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zero(m->partitions[PARTITION_USR_SECONDARY]);
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m->partitions[PARTITION_USR_VERITY] = m->partitions[PARTITION_USR_SECONDARY_VERITY];
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zero(m->partitions[PARTITION_USR_SECONDARY_VERITY]);
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} else if (m->partitions[PARTITION_USR_SECONDARY_VERITY].found)
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return -EADDRNOTAVAIL; /* as above */
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else if (flags & DISSECT_IMAGE_REQUIRE_ROOT) {
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_cleanup_free_ char *o = NULL;
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const char *options = NULL;
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/* OK, we found nothing usable, then check if there's a single generic one distro, and use
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* that. */
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/* If the root hash was set, then we won't fall back to a generic node, because the root hash
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* decides. */
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if (verity && verity->root_hash)
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return -EADDRNOTAVAIL;
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/* We didn't find a primary architecture root, but we found a primary architecture /usr? Refuse that for now. */
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if (m->partitions[PARTITION_USR].found || m->partitions[PARTITION_USR_VERITY].found)
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return -EADDRNOTAVAIL;
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/* If we didn't find a generic node, then we can't fix this up either */
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if (!generic_node)
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return -ENXIO;
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if (m->partitions[PARTITION_ROOT_SECONDARY].found) {
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/* Upgrade secondary arch to first */
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m->partitions[PARTITION_ROOT] = m->partitions[PARTITION_ROOT_SECONDARY];
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zero(m->partitions[PARTITION_ROOT_SECONDARY]);
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m->partitions[PARTITION_ROOT_VERITY] = m->partitions[PARTITION_ROOT_SECONDARY_VERITY];
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zero(m->partitions[PARTITION_ROOT_SECONDARY_VERITY]);
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/* If we didn't find a properly marked root partition, but we did find a single suitable
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* generic Linux partition, then use this as root partition, if the caller asked for it. */
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if (multiple_generic)
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return -ENOTUNIQ;
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m->partitions[PARTITION_USR] = m->partitions[PARTITION_USR_SECONDARY];
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zero(m->partitions[PARTITION_USR_SECONDARY]);
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m->partitions[PARTITION_USR_VERITY] = m->partitions[PARTITION_USR_SECONDARY_VERITY];
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zero(m->partitions[PARTITION_USR_SECONDARY_VERITY]);
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} else if (flags & DISSECT_IMAGE_REQUIRE_ROOT) {
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_cleanup_free_ char *o = NULL;
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const char *options = NULL;
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/* If the root hash was set, then we won't fall back to a generic node, because the
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* root hash decides. */
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if (verity && verity->root_hash)
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return -EADDRNOTAVAIL;
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/* If we didn't find a generic node, then we can't fix this up either */
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if (!generic_node)
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return -ENXIO;
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/* If we didn't find a properly marked root partition, but we did find a single suitable
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* generic Linux partition, then use this as root partition, if the caller asked for it. */
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if (multiple_generic)
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return -ENOTUNIQ;
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options = mount_options_from_designator(mount_options, PARTITION_ROOT);
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if (options) {
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o = strdup(options);
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if (!o)
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return -ENOMEM;
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}
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m->partitions[PARTITION_ROOT] = (DissectedPartition) {
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.found = true,
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.rw = generic_rw,
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.partno = generic_nr,
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.architecture = _ARCHITECTURE_INVALID,
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.node = TAKE_PTR(generic_node),
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.uuid = generic_uuid,
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.mount_options = TAKE_PTR(o),
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};
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options = mount_options_from_designator(mount_options, PARTITION_ROOT);
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if (options) {
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o = strdup(options);
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if (!o)
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return -ENOMEM;
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}
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m->partitions[PARTITION_ROOT] = (DissectedPartition) {
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.found = true,
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.rw = generic_rw,
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.partno = generic_nr,
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.architecture = _ARCHITECTURE_INVALID,
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.node = TAKE_PTR(generic_node),
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.uuid = generic_uuid,
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.mount_options = TAKE_PTR(o),
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};
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}
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/* Refuse if we found a verity partition for /usr but no matching file system partition */
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@@ -1397,6 +1418,32 @@ static int mount_partition(
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return 1;
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}
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static int mount_root_tmpfs(const char *where, uid_t uid_shift, DissectImageFlags flags) {
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_cleanup_free_ char *options = NULL;
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int r;
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assert(where);
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/* For images that contain /usr/ but no rootfs, let's mount rootfs as tmpfs */
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if (FLAGS_SET(flags, DISSECT_IMAGE_MKDIR)) {
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r = mkdir_p(where, 0755);
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if (r < 0)
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return r;
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}
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if (uid_is_valid(uid_shift)) {
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if (asprintf(&options, "uid=" UID_FMT ",gid=" GID_FMT, uid_shift, (gid_t) uid_shift) < 0)
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return -ENOMEM;
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}
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r = mount_nofollow_verbose(LOG_DEBUG, "rootfs", where, "tmpfs", MS_NODEV, options);
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if (r < 0)
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return r;
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return 1;
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}
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int dissected_image_mount(DissectedImage *m, const char *where, uid_t uid_shift, DissectImageFlags flags) {
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int r, xbootldr_mounted;
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@@ -1413,16 +1460,20 @@ int dissected_image_mount(DissectedImage *m, const char *where, uid_t uid_shift,
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* -EAFNOSUPPORT → File system type not supported or not known
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*/
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if (!m->partitions[PARTITION_ROOT].found)
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return -ENXIO;
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if (!(m->partitions[PARTITION_ROOT].found ||
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(m->partitions[PARTITION_USR].found && FLAGS_SET(flags, DISSECT_IMAGE_USR_NO_ROOT))))
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return -ENXIO; /* Require a root fs or at least a /usr/ fs (the latter is subject to a flag of its own) */
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if ((flags & DISSECT_IMAGE_MOUNT_NON_ROOT_ONLY) == 0) {
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r = mount_partition(m->partitions + PARTITION_ROOT, where, NULL, uid_shift, flags);
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/* First mount the root fs. If there's none we use a tmpfs. */
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if (m->partitions[PARTITION_ROOT].found)
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r = mount_partition(m->partitions + PARTITION_ROOT, where, NULL, uid_shift, flags);
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else
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r = mount_root_tmpfs(where, uid_shift, flags);
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if (r < 0)
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return r;
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}
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if ((flags & DISSECT_IMAGE_MOUNT_NON_ROOT_ONLY) == 0) {
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/* For us mounting root always means mounting /usr as well */
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r = mount_partition(m->partitions + PARTITION_USR, where, "/usr", uid_shift, flags);
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if (r < 0)
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@@ -2305,7 +2356,14 @@ int dissected_image_acquire_metadata(DissectedImage *m) {
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if (r == 0) {
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error_pipe[0] = safe_close(error_pipe[0]);
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r = dissected_image_mount(m, t, UID_INVALID, DISSECT_IMAGE_READ_ONLY|DISSECT_IMAGE_MOUNT_ROOT_ONLY|DISSECT_IMAGE_VALIDATE_OS);
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r = dissected_image_mount(
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m,
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t,
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UID_INVALID,
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DISSECT_IMAGE_READ_ONLY|
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DISSECT_IMAGE_MOUNT_ROOT_ONLY|
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DISSECT_IMAGE_VALIDATE_OS|
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DISSECT_IMAGE_USR_NO_ROOT);
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if (r < 0) {
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/* Let parent know the error */
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(void) write(error_pipe[1], &r, sizeof(r));
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@@ -87,6 +87,7 @@ typedef enum DissectImageFlags {
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DISSECT_IMAGE_NO_PARTITION_TABLE = 1 << 12, /* Only recognize single file system images */
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DISSECT_IMAGE_VERITY_SHARE = 1 << 13, /* When activating a verity device, reuse existing one if already open */
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DISSECT_IMAGE_MKDIR = 1 << 14, /* Make top-level directory to mount right before mounting, if missing */
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DISSECT_IMAGE_USR_NO_ROOT = 1 << 15, /* If no root fs is in the image, but /usr is, then allow this (so that we can mount the rootfs as tmpfs or so */
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} DissectImageFlags;
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struct DissectedImage {
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