Make unlink on directory as root set errno.

If unlink is called on an existing directory while running as root without -U
(PL_unsafe), the unlink call fails but does not set $!, because unlink(2) is
not actually called in this case.

If unlink is called as a user (or as root with -U), unlink(2) is invoked, so
attempting to remove a directory would set errno to EISDIR as expected. If
running as root without -U (PL_unsafe is false), lstat and S_ISDIR are called
instead. If the lstat succeeds and S_ISDIR returns true, the argument is
skipped without warning and without setting $!, meaning Perl's unlink can
return failure while leaving the previous value of errno in place.

This commit sets errno to EISDIR for this case.

1 files changed, 5 insertions, 1 deletions

diff --git a/doio.c b/doio.c
index 4c929b1c31..56d33b2c62 100644
--- a/doio.c
+++ b/doio.c
@@ -1821,8 +1821,12 @@ nothing in the core.
 		    tot--;
 	    }
 	    else {	/* don't let root wipe out directories without -U */
-		if (PerlLIO_lstat(s,&PL_statbuf) < 0 || S_ISDIR(PL_statbuf.st_mode))
+		if (PerlLIO_lstat(s,&PL_statbuf) < 0)
 		    tot--;
+		else if (S_ISDIR(PL_statbuf.st_mode)) {
+		    tot--;
+		    SETERRNO(EISDIR, SS$_NOPRIV);
+		}
 		else {
 		    if (UNLINK(s))
 			tot--;