4 files changed, 52 insertions, 6 deletions

diff --git a/extras/volume_id/lib/fat.c b/extras/volume_id/lib/fat.c
index e30318cf09..2d98b65b50 100644
--- a/extras/volume_id/lib/fat.c
+++ b/extras/volume_id/lib/fat.c
@@ -497,6 +497,7 @@ fat32:
 found:
 	volume_id_set_usage(id, VOLUME_ID_FILESYSTEM);
 	id->type = "vfat";
-
+	/* we think this is fat, but we make sure no other signatures are found */
+	id->force_unique_result = 1;
 	return 0;
 }
diff --git a/extras/volume_id/lib/libvolume_id-private.h b/extras/volume_id/lib/libvolume_id-private.h
index 14f7568fec..1b4a782b65 100644
--- a/extras/volume_id/lib/libvolume_id-private.h
+++ b/extras/volume_id/lib/libvolume_id-private.h
@@ -120,6 +120,7 @@ struct volume_id {
 	uint8_t		*seekbuf;
 	uint64_t	seekbuf_off;
 	size_t		seekbuf_len;
+	int		force_unique_result;
 };
 
 /* utils */
diff --git a/extras/volume_id/lib/linux_swap.c b/extras/volume_id/lib/linux_swap.c
index c4beeab978..1698e9dbf7 100644
--- a/extras/volume_id/lib/linux_swap.c
+++ b/extras/volume_id/lib/linux_swap.c
@@ -97,5 +97,7 @@ found_label:
 
 found:
 	volume_id_set_usage(id, VOLUME_ID_OTHER);
+	/* we think this is swap, but we make sure no other signatures are found */
+	id->force_unique_result = 1;
 	return 0;
 }
diff --git a/extras/volume_id/lib/volume_id.c b/extras/volume_id/lib/volume_id.c
index 8f22509ca6..e4d2ed4cfa 100644
--- a/extras/volume_id/lib/volume_id.c
+++ b/extras/volume_id/lib/volume_id.c
@@ -369,9 +369,12 @@ int volume_id_probe_raid(struct volume_id *id, uint64_t off, uint64_t size)
 
 	info("probing at offset 0x%" PRIx64 ", size 0x%" PRIx64 "\n", off, size);
 
-	for (i = 0; i < ARRAY_SIZE(prober_raid); i++)
-		if (prober_raid[i].prober(id, off, size) == 0)
+	for (i = 0; i < ARRAY_SIZE(prober_raid); i++) {
+		if (prober_raid[i].prober(id, off, size) == 0) {
+			info("signature '%s' detected\n", id->type);
 			goto found;
+		}
+	}
 	return -1;
 
 found:
@@ -402,11 +405,50 @@ int volume_id_probe_filesystem(struct volume_id *id, uint64_t off, uint64_t size
 
 	info("probing at offset 0x%" PRIx64 ", size 0x%" PRIx64 "\n", off, size);
 
-	for (i = 0; i < ARRAY_SIZE(prober_filesystem); i++)
-		if (prober_filesystem[i].prober(id, off, size) == 0)
+	/*
+	 * We probe for all known filesystems to find conflicting signatures. If
+	 * we find multiple matching signatures and one of the detected filesystem
+	 * types claims that it can not co-exist with any other filesystem type,
+	 * we do not return a probing result.
+	 *
+	 * We can not afford to mount a volume with the wrong filesystem code and
+	 * possibly corrupt it. Linux ssytems have the problem of dozens of possible
+	 * filesystem types, and volumes with left-over signatures from former
+	 * filesystem types. Invalid signature need to be removed from the volume
+	 * to make the filesystem detection successful.
+	 *
+	 * We do not want to read that many bytes from probed floppies, skip volumes
+	 * smaller than a usual floppy disk
+	 */
+	if (size > 1440 * 1024) {
+		int found = 0;
+		int force_unique_result = 0;
+
+		for (i = 0; i < ARRAY_SIZE(prober_filesystem); i++) {
+			int match;
+
+			match = (prober_filesystem[i].prober(id, off, size) == 0);
+			if (match) {
+				info("signature '%s' detected\n", id->type);
+				if (id->force_unique_result)
+					force_unique_result = id->force_unique_result;
+				if (found && force_unique_result) {
+					info("conflicting signatures found, skip results\n");
+					return -1;
+				}
+				found = 1;
+			}
+		}
+	}
+
+	/* return the first match */
+	for (i = 0; i < ARRAY_SIZE(prober_filesystem); i++) {
+		if (prober_filesystem[i].prober(id, off, size) == 0) {
+			info("signature '%s' detected\n", id->type);
 			goto found;
+		}
+	}
 	return -1;
-
 found:
 	/* If recognized, we free the allocated buffers */
 	volume_id_free_buffer(id);