dissect: rework DISSECT_IMAGE_ADD_PARTITION_DEVICES + DISSECT_IMAGE_OPEN_PARTITION_DEVICES

Curently, these two flags were implied by dissect_loop_device(), but
that's not right, because this means systemd-gpt-auto-generator will
dissect the root block device with these flags set and that's not
desirable: the generator should not cause the partition devices to be
created (we don't intend to use them right-away after all, but expect
udev to find/probe them first, and then mount them though .mount units).
And there's no point in opening the partition devices, since we do not
intend to mount them via fds either.

Hence, rework this: instead of implying the flags, specify them
explicitly.

While we are at it, let's also rename the flags to make them more
descriptive:

DISSECT_IMAGE_MANAGE_PARTITION_DEVICES becomes
DISSECT_IMAGE_ADD_PARTITION_DEVICES, since that's really all this does:
add the partition devices via BLKPG.

DISSECT_IMAGE_OPEN_PARTITION_DEVICES becomes
DISSECT_IMAGE_PIN_PARTITION_DEVICES, since we not only open the devices,
but keep the devices open continously (i.e. we "pin" them).

Also, drop the DISSECT_IMAGE_BLOCK_DEVICE combination flag, since it is
misleading, i.e. it suggests it was appropriate to specify on all
dissected blocking devices, but that's precisely not the case, see the
systemd-gpt-auto-generator case. My guess is that the confusion around
this was actually the cause for this bug we are addressing here.

Fixes: #25528

1 files changed, 14 insertions, 9 deletions

diff --git a/src/shared/dissect-image.c b/src/shared/dissect-image.c
index 4872fe4d6b..9ce9775049 100644
--- a/src/shared/dissect-image.c
+++ b/src/shared/dissect-image.c
@@ -458,7 +458,7 @@ static int dissect_image(
                         _cleanup_close_ int mount_node_fd = -1;
                         sd_id128_t uuid = SD_ID128_NULL;
 
-                        if (FLAGS_SET(flags, DISSECT_IMAGE_OPEN_PARTITION_DEVICES)) {
+                        if (FLAGS_SET(flags, DISSECT_IMAGE_PIN_PARTITION_DEVICES)) {
                                 mount_node_fd = open_partition(devname, /* is_partition = */ false, m->loop);
                                 if (mount_node_fd < 0)
                                         return mount_node_fd;
@@ -539,7 +539,7 @@ static int dissect_image(
         if (verity && verity->data_path)
                 return -EBADR;
 
-        if (FLAGS_SET(flags, DISSECT_IMAGE_MANAGE_PARTITION_DEVICES)) {
+        if (FLAGS_SET(flags, DISSECT_IMAGE_ADD_PARTITION_DEVICES)) {
                 /* Safety check: refuse block devices that carry a partition table but for which the kernel doesn't
                  * do partition scanning. */
                 r = blockdev_partscan_enabled(fd);
@@ -615,7 +615,7 @@ static int dissect_image(
                  * Kernel returns EBUSY if there's already a partition by that number or an overlapping
                  * partition already existent. */
 
-                if (FLAGS_SET(flags, DISSECT_IMAGE_MANAGE_PARTITION_DEVICES)) {
+                if (FLAGS_SET(flags, DISSECT_IMAGE_ADD_PARTITION_DEVICES)) {
                         r = block_device_add_partition(fd, node, nr, (uint64_t) start * 512, (uint64_t) size * 512);
                         if (r < 0) {
                                 if (r != -EBUSY)
@@ -870,7 +870,7 @@ static int dissect_image(
                                         dissected_partition_done(m->partitions + type.designator);
                                 }
 
-                                if (FLAGS_SET(flags, DISSECT_IMAGE_OPEN_PARTITION_DEVICES) &&
+                                if (FLAGS_SET(flags, DISSECT_IMAGE_PIN_PARTITION_DEVICES) &&
                                     type.designator != PARTITION_SWAP) {
                                         mount_node_fd = open_partition(node, /* is_partition = */ true, m->loop);
                                         if (mount_node_fd < 0)
@@ -945,7 +945,7 @@ static int dissect_image(
                                 if (m->partitions[PARTITION_XBOOTLDR].found)
                                         continue;
 
-                                if (FLAGS_SET(flags, DISSECT_IMAGE_OPEN_PARTITION_DEVICES)) {
+                                if (FLAGS_SET(flags, DISSECT_IMAGE_PIN_PARTITION_DEVICES)) {
                                         mount_node_fd = open_partition(node, /* is_partition = */ true, m->loop);
                                         if (mount_node_fd < 0)
                                                 return mount_node_fd;
@@ -1025,7 +1025,7 @@ static int dissect_image(
                         _cleanup_free_ char *o = NULL;
                         const char *options;
 
-                        if (FLAGS_SET(flags, DISSECT_IMAGE_OPEN_PARTITION_DEVICES)) {
+                        if (FLAGS_SET(flags, DISSECT_IMAGE_PIN_PARTITION_DEVICES)) {
                                 mount_node_fd = open_partition(generic_node, /* is_partition = */ true, m->loop);
                                 if (mount_node_fd < 0)
                                         return mount_node_fd;
@@ -1130,7 +1130,6 @@ int dissect_image_file(
         int r;
 
         assert(path);
-        assert((flags & DISSECT_IMAGE_BLOCK_DEVICE) == 0);
         assert(ret);
 
         fd = open(path, O_RDONLY|O_CLOEXEC|O_NONBLOCK|O_NOCTTY);
@@ -2945,7 +2944,7 @@ int dissect_loop_device(
 
         m->loop = loop_device_ref(loop);
 
-        r = dissect_image(m, loop->fd, loop->node, verity, mount_options, flags | DISSECT_IMAGE_BLOCK_DEVICE);
+        r = dissect_image(m, loop->fd, loop->node, verity, mount_options, flags);
         if (r < 0)
                 return r;
 
@@ -3108,6 +3107,10 @@ int mount_image_privately_interactively(
         assert(ret_directory);
         assert(ret_loop_device);
 
+        /* We intend to mount this right-away, hence add the partitions if needed and pin them*/
+        flags |= DISSECT_IMAGE_ADD_PARTITION_DEVICES |
+                DISSECT_IMAGE_PIN_PARTITION_DEVICES;
+
         r = verity_settings_load(&verity, image, NULL, NULL);
         if (r < 0)
                 return log_error_errno(r, "Failed to load root hash data: %m");
@@ -3202,7 +3205,9 @@ int verity_dissect_and_mount(
                 return log_debug_errno(r, "Failed to load root hash: %m");
 
         dissect_image_flags = (verity.data_path ? DISSECT_IMAGE_NO_PARTITION_TABLE : 0) |
-                (relax_extension_release_check ? DISSECT_IMAGE_RELAX_SYSEXT_CHECK : 0);
+                (relax_extension_release_check ? DISSECT_IMAGE_RELAX_SYSEXT_CHECK : 0) |
+                DISSECT_IMAGE_ADD_PARTITION_DEVICES |
+                DISSECT_IMAGE_PIN_PARTITION_DEVICES;
 
         /* Note that we don't use loop_device_make here, as the FD is most likely O_PATH which would not be
          * accepted by LOOP_CONFIGURE, so just let loop_device_make_by_path reopen it as a regular FD. */