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, 12 insertions, 3 deletions

diff --git a/util-linux/volume_id/util.c b/util-linux/volume_id/util.c
index 315d75ca6..c4d20ba47 100644
--- a/util-linux/volume_id/util.c
+++ b/util-linux/volume_id/util.c
@@ -181,7 +181,7 @@ set:
                         buf[4], buf[5],
                         buf[6], buf[7],
                         buf[8], buf[9],
-                        buf[10], buf[11], buf[12], buf[13], buf[14],buf[15]);
+                        buf[10], buf[11], buf[12], buf[13], buf[14], buf[15]);
                 break;
         case UUID_DCE_STRING:
                 memcpy(id->uuid, buf, count);
@@ -190,6 +190,9 @@ set:
         }
 }
 
+/* Do not use xlseek here. With it, single corrupted filesystem
+ * may result in attempt to seek past device -> exit.
+ * It's better to ignore such fs and continue.  */
 void *volume_id_get_buffer(struct volume_id *id, uint64_t off, size_t len)
 {
         ssize_t buf_len;
@@ -204,7 +207,10 @@ void *volume_id_get_buffer(struct volume_id *id, uint64_t off, size_t len)
                 /* check if we need to read */
                 if ((off + len) > id->sbbuf_len) {
                         dbg("read sbbuf len:0x%llx", (unsigned long long) (off + len));
-                        xlseek(id->fd, 0, SEEK_SET);
+                        if (lseek(id->fd, 0, SEEK_SET) != 0) {
+                                dbg("seek(0) failed");
+                                return NULL;
+                        }
                         buf_len = full_read(id->fd, id->sbbuf, off + len);
                         if (buf_len < 0) {
                                 dbg("read failed (%s)", strerror(errno));
@@ -234,7 +240,10 @@ void *volume_id_get_buffer(struct volume_id *id, uint64_t off, size_t len)
         /* check if we need to read */
         if ((off < id->seekbuf_off) || ((off + len) > (id->seekbuf_off + id->seekbuf_len))) {
                 dbg("read seekbuf off:0x%llx len:0x%zx", (unsigned long long) off, len);
-                xlseek(id->fd, off, SEEK_SET);
+                if (lseek(id->fd, off, SEEK_SET) != off) {
+                        dbg("seek(0x%llx) failed", (unsigned long long) off);
+                        return NULL;
+                }
                 buf_len = full_read(id->fd, id->seekbuf, len);
                 if (buf_len < 0) {
                         dbg("read failed (%s)", strerror(errno));