Use full-read instead of safe-read

This helps handle archiving on certain filesystems where read()
returns less bytes than requested when reading from a regular
file.

References:

  https://savannah.gnu.org/bugs/index.php?64426
  https://lists.gnu.org/archive/html/bug-tar/2021-07/msg00001.html

* gnulib.modules: Add full-read.
* src/common.h: Include full-read.h
* src/misc.c: Use full_read.
* src/sparse.c: Likewise.
* src/update.c: Likewise.

gnulib.modules

@@ -79,7 +79,7 @@ readlinkat
 renameat
 root-uid
 rpmatch
-safe-read
+full-read
 savedir
 selinux-at
 setenv

src/common.h

@@ -58,6 +58,7 @@
 #include <modechange.h>
 #include <quote.h>
 #include <safe-read.h>
+#include <full-read.h>
 #include <stat-time.h>
 #include <timespec.h>
 #define obstack_chunk_alloc xmalloc

src/misc.c

@@ -821,7 +821,7 @@ deref_stat (char const *name, struct stat *buf)
 size_t
 blocking_read (int fd, void *buf, size_t count)
 {
-  size_t bytes = safe_read (fd, buf, count);
+  size_t bytes = full_read (fd, buf, count);
 
 #if defined F_SETFL && O_NONBLOCK
   if (bytes == SAFE_READ_ERROR && errno == EAGAIN)
@@ -829,10 +829,12 @@ blocking_read (int fd, void *buf, size_t count)
       int flags = fcntl (fd, F_GETFL);
       if (0 <= flags && flags & O_NONBLOCK
 	  && fcntl (fd, F_SETFL, flags & ~O_NONBLOCK) != -1)
-	bytes = safe_read (fd, buf, count);
+	bytes = full_read (fd, buf, count);
     }
 #endif
 
+  if (bytes == 0 && errno != 0)
+    bytes = SAFE_READ_ERROR;
   return bytes;
 }
 

src/sparse.c

@@ -415,7 +415,7 @@ sparse_dump_region (struct tar_sparse_file *file, size_t i)
       size_t bytes_read;
 
       blk = find_next_block ();
-      bytes_read = safe_read (file->fd, blk->buffer, bufsize);
+      bytes_read = full_read (file->fd, blk->buffer, bufsize);
       if (bytes_read == SAFE_READ_ERROR)
 	{
           read_diag_details (file->stat_info->orig_file_name,
@@ -427,27 +427,39 @@ sparse_dump_region (struct tar_sparse_file *file, size_t i)
 	}
       else if (bytes_read == 0)
 	{
-	  char buf[UINTMAX_STRSIZE_BOUND];
-	  struct stat st;
-	  size_t n;
-	  if (fstat (file->fd, &st) == 0)
-	    n = file->stat_info->stat.st_size - st.st_size;
+	  if (errno != 0)
+	    {
+	      read_diag_details (file->stat_info->orig_file_name,
+				 (file->stat_info->sparse_map[i].offset
+				  + file->stat_info->sparse_map[i].numbytes
+				  - bytes_left),
+				 bufsize);
+	      return false;
+	    }
 	  else
-	    n = file->stat_info->stat.st_size
-	      - (file->stat_info->sparse_map[i].offset
-		 + file->stat_info->sparse_map[i].numbytes
-		 - bytes_left);
-
-	  WARNOPT (WARN_FILE_SHRANK,
-		   (0, 0,
-		    ngettext ("%s: File shrank by %s byte; padding with zeros",
-			      "%s: File shrank by %s bytes; padding with zeros",
-			      n),
-		    quotearg_colon (file->stat_info->orig_file_name),
-		    STRINGIFY_BIGINT (n, buf)));
-	  if (! ignore_failed_read_option)
-	    set_exit_status (TAREXIT_DIFFERS);
-	  return false;
+	    {
+	      char buf[UINTMAX_STRSIZE_BOUND];
+	      struct stat st;
+	      size_t n;
+	      if (fstat (file->fd, &st) == 0)
+		n = file->stat_info->stat.st_size - st.st_size;
+	      else
+		n = file->stat_info->stat.st_size
+		  - (file->stat_info->sparse_map[i].offset
+		     + file->stat_info->sparse_map[i].numbytes
+		     - bytes_left);
+
+	      WARNOPT (WARN_FILE_SHRANK,
+		       (0, 0,
+			ngettext ("%s: File shrank by %s byte; padding with zeros",
+				  "%s: File shrank by %s bytes; padding with zeros",
+				  n),
+			quotearg_colon (file->stat_info->orig_file_name),
+			STRINGIFY_BIGINT (n, buf)));
+	      if (! ignore_failed_read_option)
+		set_exit_status (TAREXIT_DIFFERS);
+	      return false;
+	    }
 	}
 
       memset (blk->buffer + bytes_read, 0, BLOCKSIZE - bytes_read);
@@ -615,7 +627,7 @@ check_sparse_region (struct tar_sparse_file *file, off_t beg, off_t end)
       size_t rdsize = BLOCKSIZE < end - beg ? BLOCKSIZE : end - beg;
       char diff_buffer[BLOCKSIZE];
 
-      bytes_read = safe_read (file->fd, diff_buffer, rdsize);
+      bytes_read = full_read (file->fd, diff_buffer, rdsize);
       if (bytes_read == SAFE_READ_ERROR)
 	{
           read_diag_details (file->stat_info->orig_file_name,
@@ -625,7 +637,12 @@ check_sparse_region (struct tar_sparse_file *file, off_t beg, off_t end)
 	}
       else if (bytes_read == 0)
 	{
-	  report_difference (file->stat_info, _("Size differs"));
+	  if (errno != 0)
+	    read_diag_details (file->stat_info->orig_file_name,
+			       beg,
+			       rdsize);
+	  else
+	    report_difference (file->stat_info, _("Size differs"));
 	  return false;
 	}
 
@@ -668,7 +685,7 @@ check_data_region (struct tar_sparse_file *file, size_t i)
 	}
       set_next_block_after (blk);
       file->dumped_size += BLOCKSIZE;
-      bytes_read = safe_read (file->fd, diff_buffer, rdsize);
+      bytes_read = full_read (file->fd, diff_buffer, rdsize);
       if (bytes_read == SAFE_READ_ERROR)
 	{
           read_diag_details (file->stat_info->orig_file_name,
@@ -680,7 +697,14 @@ check_data_region (struct tar_sparse_file *file, size_t i)
 	}
       else if (bytes_read == 0)
 	{
-	  report_difference (&current_stat_info, _("Size differs"));
+	  if (errno != 0)
+	    read_diag_details (file->stat_info->orig_file_name,
+			       (file->stat_info->sparse_map[i].offset
+				+ file->stat_info->sparse_map[i].numbytes
+				- size_left),
+			       rdsize);
+	  else
+	    report_difference (&current_stat_info, _("Size differs"));
 	  return false;
 	}
       size_left -= bytes_read;

src/update.c

@@ -60,10 +60,14 @@ append_file (char *file_name)
   while (true)
     {
       union block *start = find_next_block ();
-      size_t status = safe_read (handle, start->buffer,
+      size_t status = full_read (handle, start->buffer,
 				 available_space_after (start));
       if (status == 0)
-	break;
+	{
+	  if (errno == 0)
+	    break;
+	  read_fatal (file_name);
+	}
       if (status == SAFE_READ_ERROR)
 	read_fatal (file_name);
       if (status % BLOCKSIZE)