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 9ab1cef02..816d69d4c 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;