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, 37 insertions, 13 deletions

diff --git a/util-linux/volume_id/luks.c b/util-linux/volume_id/luks.c
index 51dda4e79..b0f0f5b21 100644
--- a/util-linux/volume_id/luks.c
+++ b/util-linux/volume_id/luks.c
@@ -20,20 +20,16 @@
 
 #include "volume_id_internal.h"
 
-#define SECTOR_SHIFT                    9
-#define SECTOR_SIZE                     (1 << SECTOR_SHIFT)
-
-#define LUKS_CIPHERNAME_L               32
-#define LUKS_CIPHERMODE_L               32
-#define LUKS_HASHSPEC_L                 32
-#define LUKS_DIGESTSIZE                 20
-#define LUKS_SALTSIZE                   32
-#define LUKS_NUMKEYS                    8
+#define LUKS_MAGIC_L             6
+#define UUID_STRING_L           40
+#define LUKS_CIPHERNAME_L       32
+#define LUKS_CIPHERMODE_L       32
+#define LUKS_HASHSPEC_L         32
+#define LUKS_DIGESTSIZE         20
+#define LUKS_SALTSIZE           32
+#define LUKS_NUMKEYS             8
 
 static const uint8_t LUKS_MAGIC[] = { 'L','U','K','S', 0xba, 0xbe };
-#define LUKS_MAGIC_L 6
-#define LUKS_PHDR_SIZE (sizeof(struct luks_phdr)/SECTOR_SIZE+1)
-#define UUID_STRING_L 40
 
 struct luks_phdr {
         uint8_t         magic[LUKS_MAGIC_L];
@@ -56,11 +52,39 @@ struct luks_phdr {
         } keyblock[LUKS_NUMKEYS];
 };
 
+enum {
+        EXPECTED_SIZE_luks_phdr = 0
+                + 1 * LUKS_MAGIC_L
+                + 2
+                + 1 * LUKS_CIPHERNAME_L
+                + 1 * LUKS_CIPHERMODE_L
+                + 1 * LUKS_HASHSPEC_L
+                + 4
+                + 4
+                + 1 * LUKS_DIGESTSIZE
+                + 1 * LUKS_SALTSIZE
+                + 4
+                + 1 * UUID_STRING_L
+                + LUKS_NUMKEYS * (0
+                  + 4
+                  + 4
+                  + 1 * LUKS_SALTSIZE
+                  + 4
+                  + 4
+                  )
+};
+
+struct BUG_bad_size_luks_phdr {
+        char BUG_bad_size_luks_phdr[
+                sizeof(struct luks_phdr) == EXPECTED_SIZE_luks_phdr ?
+                1 : -1];
+};
+
 int volume_id_probe_luks(struct volume_id *id, uint64_t off)
 {
         struct luks_phdr *header;
 
-        header = volume_id_get_buffer(id, off, LUKS_PHDR_SIZE);
+        header = volume_id_get_buffer(id, off, sizeof(*header));
         if (header == NULL)
                 return -1;