safe_macros: Fix safe_write()

- Add return to the if (rval == -1) branch

  If we are in a cleanup the tst_brkm_() will return back and we will
  continue and print more tst_brkm_() messages particulary the "short
  write()" in the case of SAFE_WRITE_ALL

- Add check for invalid return value (rval < 0)

  This will not happen unless there is a bug in libc but we should check
  for it anyways.

- Remove TERRNO from the short write tst_brkm_()

  Since in a case of a short write the errno is not defined and we will
  print whatever was left there.

Signed-off-by: Cyril Hrubis <chrubis@suse.cz>
Reviewed-by: Petr Vorel <pvorel@suse.cz>
Link: https://lore.kernel.org/ltp/20250109150336.25235-1-chrubis@suse.cz/

Author: metan-ucw

lib/safe_macros.c

@@ -551,14 +551,22 @@ ssize_t safe_write(const char *file, const int lineno, void (cleanup_fn) (void),
 			tst_brkm_(file, lineno, TBROK | TERRNO,
 				cleanup_fn, "write(%d,%p,%zu) failed",
 				fildes, buf, nbyte);
+			return rval;
+		}
+
+		if (rval < 0) {
+			tst_brkm_(file, lineno, TBROK, cleanup_fn,
+			          "invalid write() return value %zi",
+				  rval);
+			return rval;
 		}
 
 		if (len_strict == SAFE_WRITE_ANY)
 			return rval;
 
 		if (len_strict == SAFE_WRITE_ALL) {
 			if ((size_t)rval != nbyte)
-				tst_brkm_(file, lineno, TBROK | TERRNO,
+				tst_brkm_(file, lineno, TBROK,
 					cleanup_fn, "short write(%d,%p,%zu) "
 					"return value %zd",
 					fildes, buf, nbyte, rval);