dissect-image: return error if results are ambiguous

We let the caller make the decision. Existing callers are OK with treating an
ambiguous result the same as no content, but makefs and growfs should refuse such
partitions.

3 files changed, 19 insertions, 5 deletions

diff --git a/src/partition/growfs.c b/src/partition/growfs.c
index f9c604ca6f..8b44c1ded7 100644
--- a/src/partition/growfs.c
+++ b/src/partition/growfs.c
@@ -151,6 +151,8 @@ static int maybe_resize_slave_device(const char *mountpath, dev_t main_devno) {
 
         xsprintf_dev_num_path(devpath, "block", devno);
         r = probe_filesystem(devpath, &fstype);
+        if (r == -EUCLEAN)
+                return log_warning_errno(r, "Cannot reliably determine probe \"%s\", refusing to proceed.", devpath);
         if (r < 0)
                 return log_warning_errno(r, "Failed to probe \"%s\": %m", devpath);
 
diff --git a/src/partition/makefs.c b/src/partition/makefs.c
index c24c6ebcde..e5e125255b 100644
--- a/src/partition/makefs.c
+++ b/src/partition/makefs.c
@@ -90,7 +90,11 @@ int main(int argc, char *argv[]) {
 
         r = probe_filesystem(device, &detected);
         if (r < 0) {
-                log_warning_errno(r, "Failed to probe \"%s\": %m", device);
+                log_warning_errno(r,
+                                  r == -EUCLEAN ?
+                                  "Cannot reliably determine probe \"%s\", refusing to proceed." :
+                                  "Failed to probe \"%s\": %m",
+                                  device);
                 goto finish;
         }
 
diff --git a/src/shared/dissect-image.c b/src/shared/dissect-image.c
index 3c16f60b83..7835d99020 100644
--- a/src/shared/dissect-image.c
+++ b/src/shared/dissect-image.c
@@ -52,6 +52,10 @@
 #include "xattr-util.h"
 
 int probe_filesystem(const char *node, char **ret_fstype) {
+        /* Try to find device content type and return it in *ret_fstype. If nothing is found,
+         * 0/NULL will be returned. -EUCLEAN will be returned for ambigous results, and an
+         * different error otherwise. */
+
 #if HAVE_BLKID
         _cleanup_blkid_free_probe_ blkid_probe b = NULL;
         const char *fstype;
@@ -67,10 +71,14 @@ int probe_filesystem(const char *node, char **ret_fstype) {
 
         errno = 0;
         r = blkid_do_safeprobe(b);
-        if (IN_SET(r, -2, 1)) {
-                log_debug("Failed to identify any partition type on partition %s", node);
+        if (r == 1) {
+                log_debug("No type detected on partition %s", node);
                 goto not_found;
         }
+        if (r == -2) {
+                log_debug("Results ambiguous for partition %s", node);
+                return -EUCLEAN;
+        }
         if (r != 0)
                 return -errno ?: -EIO;
 
@@ -608,7 +616,7 @@ int dissect_image(int fd, const void *root_hash, size_t root_hash_size, DissectI
 
                 if (!p->fstype && p->node) {
                         r = probe_filesystem(p->node, &p->fstype);
-                        if (r < 0)
+                        if (r < 0 && r != -EUCLEAN)
                                 return r;
                 }
 
@@ -1018,7 +1026,7 @@ int dissected_image_decrypt(
 
                 if (!p->decrypted_fstype && p->decrypted_node) {
                         r = probe_filesystem(p->decrypted_node, &p->decrypted_fstype);
-                        if (r < 0)
+                        if (r < 0 && r != -EUCLEAN)
                                 return r;
                 }
         }