tar/tar-1.27.1-sparse-inf-loops.patch

diff --git a/THANKS b/THANKS
index a734fb6..2da6100 100644
--- a/THANKS
+++ b/THANKS
@@ -173,6 +173,7 @@ Fabio d'Alessi		cars@civ.bio.unipd.it
 Frank Heckenbach	frank@g-n-u.de
 Frank Koenen		koenfr@lidp.com
 Franz-Werner Gergen	gergen@edvulx.mpi-stuttgart.mpg.de
+François Ouellet	fouell@gmail.com
 François Pinard		pinard@iro.umontreal.ca
 Fritz Elfert		fritz@fsun.triltsch.de
 George Chyu		gschyu@ccgate.dp.beckman.com
diff --git a/src/sparse.c b/src/sparse.c
index f0268f4..250e845 100644
--- a/src/sparse.c
+++ b/src/sparse.c
@@ -301,6 +301,7 @@ sparse_dump_region (struct tar_sparse_file *file, size_t i)
 {
   union block *blk;
   off_t bytes_left = file->stat_info->sparse_map[i].numbytes;
+  const char *file_name = file->stat_info->orig_file_name;
 
   if (!lseek_or_error (file, file->stat_info->sparse_map[i].offset))
     return false;
@@ -314,13 +315,23 @@ sparse_dump_region (struct tar_sparse_file *file, size_t i)
       bytes_read = safe_read (file->fd, blk->buffer, bufsize);
       if (bytes_read == SAFE_READ_ERROR)
 	{
-          read_diag_details (file->stat_info->orig_file_name,
+          read_diag_details (file_name,
 	                     (file->stat_info->sparse_map[i].offset
 			      + file->stat_info->sparse_map[i].numbytes
 			      - bytes_left),
 			     bufsize);
 	  return false;
 	}
+      if (bytes_read == 0)
+        {
+          char buf[UINTMAX_STRSIZE_BOUND];
+          FATAL_ERROR ((0, 0,
+                        ngettext ("%s: File shrank by %s byte",
+                                  "%s: File shrank by %s bytes",
+                                  bytes_left),
+                        quotearg_colon (file_name),
+                        offtostr (bytes_left, buf)));
+        }
 
       memset (blk->buffer + bytes_read, 0, BLOCKSIZE - bytes_read);
       bytes_left -= bytes_read;
@@ -475,33 +486,37 @@ sparse_skip_file (struct tar_stat_info *st)
 static bool
 check_sparse_region (struct tar_sparse_file *file, off_t beg, off_t end)
 {
-  if (!lseek_or_error (file, beg))
+  off_t offset = beg;
+
+  if (!lseek_or_error (file, offset))
     return false;
 
-  while (beg < end)
+  while (offset < end)
     {
       size_t bytes_read;
-      size_t rdsize = BLOCKSIZE < end - beg ? BLOCKSIZE : end - beg;
+      size_t rdsize = BLOCKSIZE < end - offset ? BLOCKSIZE : end - offset;
       char diff_buffer[BLOCKSIZE];
 
       bytes_read = safe_read (file->fd, diff_buffer, rdsize);
       if (bytes_read == SAFE_READ_ERROR)
 	{
           read_diag_details (file->stat_info->orig_file_name,
-	                     beg,
-			     rdsize);
-	  return false;
-	}
-      if (!zero_block_p (diff_buffer, bytes_read))
-	{
-	  char begbuf[INT_BUFSIZE_BOUND (off_t)];
- 	  report_difference (file->stat_info,
-			     _("File fragment at %s is not a hole"),
-			     offtostr (beg, begbuf));
+	                     offset, rdsize);
 	  return false;
 	}
 
-      beg += bytes_read;
+      if (bytes_read == 0
+          || !zero_block_p (diff_buffer, bytes_read))
+        {
+          char begbuf[INT_BUFSIZE_BOUND (off_t)];
+          const char *msg = bytes_read ? _("File fragment at %s is not a hole")
+                                       : _("Hole starting at %s is truncated");
+
+          report_difference (file->stat_info, msg, offtostr (beg, begbuf));
+          return false;
+        }
+
+      offset += bytes_read;
     }
   return true;
 }
@@ -542,7 +557,8 @@ check_data_region (struct tar_sparse_file *file, size_t i)
       file->dumped_size += bytes_read;
       size_left -= bytes_read;
       mv_size_left (file->stat_info->archive_file_size - file->dumped_size);
-      if (memcmp (blk->buffer, diff_buffer, rdsize))
+      if (bytes_read == 0
+          || memcmp (blk->buffer, diff_buffer, bytes_read))
 	{
 	  report_difference (file->stat_info, _("Contents differ"));
 	  return false;