vol_id: probe volume as user nobody

Signed-off-by: Kay Sievers <kay.sievers@suse.de>

extras/volume_id/libvolume_id/mac.c

@@ -84,14 +84,15 @@ int volume_id_probe_mac_partition_map(struct volume_id *id, uint64_t off)
 
 		part_count = be32_to_cpu(part->map_count);
 		dbg("expecting %d partition entries", part_count);
+		if (part_count < 1 || part_count > 256)
+			return -1;
 
 		if (id->partitions != NULL)
 			free(id->partitions);
-		id->partitions =
-			malloc(part_count * sizeof(struct volume_id_partition));
+		id->partitions = malloc(part_count * sizeof(struct volume_id_partition));
 		if (id->partitions == NULL)
 			return -1;
-		memset(id->partitions, 0x00, sizeof(struct volume_id_partition));
+		memset(id->partitions, 0x00, part_count * sizeof(struct volume_id_partition));
 
 		id->partition_count = part_count;
 

extras/volume_id/libvolume_id/volume_id.h

@@ -14,7 +14,7 @@
 #include <stdint.h>
 #include <stddef.h>
 
-#define VOLUME_ID_VERSION		55
+#define VOLUME_ID_VERSION		56
 
 #define VOLUME_ID_LABEL_SIZE		64
 #define VOLUME_ID_UUID_SIZE		36

extras/volume_id/vol_id.c

@@ -27,6 +27,7 @@
 #include <unistd.h>
 #include <string.h>
 #include <ctype.h>
+#include <grp.h>
 #include <sys/ioctl.h>
 
 #include "../../udev.h"
@@ -110,6 +111,8 @@ int main(int argc, char *argv[])
 	int i;
 	uint64_t size;
 	const char *node = NULL;
+	uid_t nobody_uid;
+	gid_t nobody_gid;
 	int rc = 0;
 
 	logging_init("vol_id");
@@ -146,12 +149,24 @@ int main(int argc, char *argv[])
 		size = 0;
 	dbg("BLKGETSIZE64=%llu", size);
 
+	/* drop all privileges */
+	nobody_uid = lookup_user("nobody");
+	nobody_gid = lookup_group("nogroup");
+	if (nobody_uid > 0 && nobody_gid > 0) {
+		if (setgroups(0, NULL) != 0 ||
+		    setgid(nobody_gid) != 0 ||
+		    setuid(nobody_uid) != 0) {
+			rc = 3;
+			goto exit;
+		}
+	}
+
 	if (volume_id_probe_all(vid, 0, size) == 0)
 		goto print;
 
 	if (print != PRINT_EXPORT)
 		fprintf(stderr, "%s: unknown volume type\n", node);
-	rc = 3;
+	rc = 4;
 	goto exit;
 
 print: