findfs: fix LUKS and FAT detection routines; do not exit if corrupted

 FAT fs makes us try to seek past volume

function                                             old     new   delta
volume_id_get_buffer                                 301     327     +26
volume_id_probe_luks                                  79      82      +3
get_attr_volume_id                                    73      65      -8
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/1 up/down: 29/-8)              Total: 21 bytes

1 files changed, 62 insertions, 66 deletions

diff --git a/util-linux/volume_id/fat.c b/util-linux/volume_id/fat.c
index 9ab1cef..816d69d 100644
--- a/util-linux/volume_id/fat.c
+++ b/util-linux/volume_id/fat.c
@@ -20,8 +20,11 @@
 
 #include "volume_id_internal.h"
 
-#define FAT12_MAX			0xff5
-#define FAT16_MAX			0xfff5
+/* linux/msdos_fs.h says: */
+#define FAT12_MAX			0xff4
+#define FAT16_MAX			0xfff4
+#define FAT32_MAX			0x0ffffff6
+
 #define FAT_ATTR_VOLUME_ID		0x08
 #define FAT_ATTR_DIR			0x10
 #define FAT_ATTR_LONG_NAME		0x0f
@@ -31,9 +34,9 @@
 struct vfat_super_block {
 	uint8_t		boot_jump[3];
 	uint8_t		sysid[8];
-	uint16_t	sector_size;
+	uint16_t	sector_size_bytes;
 	uint8_t		sectors_per_cluster;
-	uint16_t	reserved;
+	uint16_t	reserved_sct;
 	uint8_t		fats;
 	uint16_t	dir_entries;
 	uint16_t	sectors;
@@ -84,32 +87,30 @@ struct vfat_dir_entry {
 	uint32_t	size;
 } __attribute__((__packed__));
 
-static uint8_t *get_attr_volume_id(struct vfat_dir_entry *dir, unsigned count)
+static uint8_t *get_attr_volume_id(struct vfat_dir_entry *dir, int count)
 {
-	unsigned i;
-
-	for (i = 0; i < count; i++) {
+	for (;--count >= 0; dir++) {
 		/* end marker */
-		if (dir[i].name[0] == 0x00) {
+		if (dir->name[0] == 0x00) {
 			dbg("end of dir");
 			break;
 		}
 
 		/* empty entry */
-		if (dir[i].name[0] == FAT_ENTRY_FREE)
+		if (dir->name[0] == FAT_ENTRY_FREE)
 			continue;
 
 		/* long name */
-		if ((dir[i].attr & FAT_ATTR_MASK) == FAT_ATTR_LONG_NAME)
+		if ((dir->attr & FAT_ATTR_MASK) == FAT_ATTR_LONG_NAME)
 			continue;
 
-		if ((dir[i].attr & (FAT_ATTR_VOLUME_ID | FAT_ATTR_DIR)) == FAT_ATTR_VOLUME_ID) {
+		if ((dir->attr & (FAT_ATTR_VOLUME_ID | FAT_ATTR_DIR)) == FAT_ATTR_VOLUME_ID) {
 			/* labels do not have file data */
-			if (dir[i].cluster_high != 0 || dir[i].cluster_low != 0)
+			if (dir->cluster_high != 0 || dir->cluster_low != 0)
 				continue;
 
 			dbg("found ATTR_VOLUME_ID id in root dir");
-			return dir[i].name;
+			return dir->name;
 		}
 
 		dbg("skip dir entry");
@@ -118,31 +119,29 @@ static uint8_t *get_attr_volume_id(struct vfat_dir_entry *dir, unsigned count)
 	return NULL;
 }
 
-int volume_id_probe_vfat(struct volume_id *id, uint64_t off)
+int volume_id_probe_vfat(struct volume_id *id, uint64_t fat_partition_off)
 {
 	struct vfat_super_block *vs;
 	struct vfat_dir_entry *dir;
-	uint16_t sector_size;
+	uint16_t sector_size_bytes;
 	uint16_t dir_entries;
 	uint32_t sect_count;
-	uint16_t reserved;
-	uint32_t fat_size;
+	uint16_t reserved_sct;
+	uint32_t fat_size_sct;
 	uint32_t root_cluster;
-	uint32_t dir_size;
+	uint32_t dir_size_sct;
 	uint32_t cluster_count;
-	uint32_t fat_length;
-	uint64_t root_start;
-	uint32_t start_data_sect;
-	uint16_t root_dir_entries;
+	uint64_t root_start_off;
+	uint32_t start_data_sct;
 	uint8_t *buf;
 	uint32_t buf_size;
 	uint8_t *label = NULL;
-	uint32_t next;
+	uint32_t next_cluster;
 	int maxloop;
 
-	dbg("probing at offset 0x%llx", (unsigned long long) off);
+	dbg("probing at offset 0x%llx", (unsigned long long) fat_partition_off);
 
-	vs = volume_id_get_buffer(id, off, 0x200);
+	vs = volume_id_get_buffer(id, fat_partition_off, 0x200);
 	if (vs == NULL)
 		return -1;
 
@@ -196,34 +195,34 @@ int volume_id_probe_vfat(struct volume_id *id, uint64_t off)
 
  valid:
 	/* sector size check */
-	sector_size = le16_to_cpu(vs->sector_size);
-	if (sector_size != 0x200 && sector_size != 0x400 &&
-	    sector_size != 0x800 && sector_size != 0x1000)
+	sector_size_bytes = le16_to_cpu(vs->sector_size_bytes);
+	if (sector_size_bytes != 0x200 && sector_size_bytes != 0x400 &&
+	    sector_size_bytes != 0x800 && sector_size_bytes != 0x1000)
 		return -1;
 
-	dbg("sector_size 0x%x", sector_size);
+	dbg("sector_size_bytes 0x%x", sector_size_bytes);
 	dbg("sectors_per_cluster 0x%x", vs->sectors_per_cluster);
 
-	dir_entries = le16_to_cpu(vs->dir_entries);
-	reserved = le16_to_cpu(vs->reserved);
-	dbg("reserved 0x%x", reserved);
+	reserved_sct = le16_to_cpu(vs->reserved_sct);
+	dbg("reserved_sct 0x%x", reserved_sct);
 
 	sect_count = le16_to_cpu(vs->sectors);
 	if (sect_count == 0)
 		sect_count = le32_to_cpu(vs->total_sect);
 	dbg("sect_count 0x%x", sect_count);
 
-	fat_length = le16_to_cpu(vs->fat_length);
-	if (fat_length == 0)
-		fat_length = le32_to_cpu(vs->type.fat32.fat32_length);
-	dbg("fat_length 0x%x", fat_length);
+	fat_size_sct = le16_to_cpu(vs->fat_length);
+	if (fat_size_sct == 0)
+		fat_size_sct = le32_to_cpu(vs->type.fat32.fat32_length);
+	fat_size_sct *= vs->fats;
+	dbg("fat_size_sct 0x%x", fat_size_sct);
 
-	fat_size = fat_length * vs->fats;
-	dir_size = ((dir_entries * sizeof(struct vfat_dir_entry)) +
-			(sector_size-1)) / sector_size;
-	dbg("dir_size 0x%x", dir_size);
+	dir_entries = le16_to_cpu(vs->dir_entries);
+	dir_size_sct = ((dir_entries * sizeof(struct vfat_dir_entry)) +
+			(sector_size_bytes-1)) / sector_size_bytes;
+	dbg("dir_size_sct 0x%x", dir_size_sct);
 
-	cluster_count = sect_count - (reserved + fat_size + dir_size);
+	cluster_count = sect_count - (reserved_sct + fat_size_sct + dir_size_sct);
 	cluster_count /= vs->sectors_per_cluster;
 	dbg("cluster_count 0x%x", cluster_count);
 
@@ -239,21 +238,18 @@ int volume_id_probe_vfat(struct volume_id *id, uint64_t off)
 		goto fat32;
 
 	/* the label may be an attribute in the root directory */
-	root_start = (reserved + fat_size) * sector_size;
-	dbg("root dir start 0x%llx", (unsigned long long) root_start);
-	root_dir_entries = le16_to_cpu(vs->dir_entries);
-	dbg("expected entries 0x%x", root_dir_entries);
+	root_start_off = (reserved_sct + fat_size_sct) * sector_size_bytes;
+	dbg("root dir start 0x%llx", (unsigned long long) root_start_off);
+	dbg("expected entries 0x%x", dir_entries);
 
-	buf_size = root_dir_entries * sizeof(struct vfat_dir_entry);
-	buf = volume_id_get_buffer(id, off + root_start, buf_size);
+	buf_size = dir_entries * sizeof(struct vfat_dir_entry);
+	buf = volume_id_get_buffer(id, fat_partition_off + root_start_off, buf_size);
 	if (buf == NULL)
 		goto found;
 
-	dir = (struct vfat_dir_entry*) buf;
-
-	label = get_attr_volume_id(dir, root_dir_entries);
+	label = get_attr_volume_id((struct vfat_dir_entry*) buf, dir_entries);
 
-	vs = volume_id_get_buffer(id, off, 0x200);
+	vs = volume_id_get_buffer(id, fat_partition_off, 0x200);
 	if (vs == NULL)
 		return -1;
 
@@ -269,26 +265,25 @@ int volume_id_probe_vfat(struct volume_id *id, uint64_t off)
 
  fat32:
 	/* FAT32 root dir is a cluster chain like any other directory */
-	buf_size = vs->sectors_per_cluster * sector_size;
+	buf_size = vs->sectors_per_cluster * sector_size_bytes;
 	root_cluster = le32_to_cpu(vs->type.fat32.root_cluster);
-	dbg("root dir cluster %u", root_cluster);
-	start_data_sect = reserved + fat_size;
+	start_data_sct = reserved_sct + fat_size_sct;
 
-	next = root_cluster;
+	next_cluster = root_cluster;
 	maxloop = 100;
 	while (--maxloop) {
-		uint32_t next_sect_off;
+		uint32_t next_off_sct;
 		uint64_t next_off;
 		uint64_t fat_entry_off;
 		int count;
 
-		dbg("next cluster %u", next);
-		next_sect_off = (next - 2) * vs->sectors_per_cluster;
-		next_off = (start_data_sect + next_sect_off) * sector_size;
+		dbg("next_cluster 0x%x", (unsigned)next_cluster);
+		next_off_sct = (next_cluster - 2) * vs->sectors_per_cluster;
+		next_off = (start_data_sct + next_off_sct) * sector_size_bytes;
 		dbg("cluster offset 0x%llx", (unsigned long long) next_off);
 
 		/* get cluster */
-		buf = volume_id_get_buffer(id, off + next_off, buf_size);
+		buf = volume_id_get_buffer(id, fat_partition_off + next_off, buf_size);
 		if (buf == NULL)
 			goto found;
 
@@ -301,20 +296,21 @@ int volume_id_probe_vfat(struct volume_id *id, uint64_t off)
 			break;
 
 		/* get FAT entry */
-		fat_entry_off = (reserved * sector_size) + (next * sizeof(uint32_t));
-		buf = volume_id_get_buffer(id, off + fat_entry_off, buf_size);
+		fat_entry_off = (reserved_sct * sector_size_bytes) + (next_cluster * sizeof(uint32_t));
+		dbg("fat_entry_off 0x%llx", (unsigned long long)fat_entry_off);
+		buf = volume_id_get_buffer(id, fat_partition_off + fat_entry_off, buf_size);
 		if (buf == NULL)
 			goto found;
 
 		/* set next cluster */
-		next = le32_to_cpu(*((uint32_t *) buf) & 0x0fffffff);
-		if (next == 0)
+		next_cluster = le32_to_cpu(*(uint32_t*)buf) & 0x0fffffff;
+		if (next_cluster < 2 || next_cluster > FAT32_MAX)
 			break;
 	}
 	if (maxloop == 0)
 		dbg("reached maximum follow count of root cluster chain, give up");
 
-	vs = volume_id_get_buffer(id, off, 0x200);
+	vs = volume_id_get_buffer(id, fat_partition_off, 0x200);
 	if (vs == NULL)
 		return -1;