don't taint $$ determined by getpid()

Reading $$ in a tainted expression was tainting the internal sv_setiv()
on $$.  Since the value being set came directly from getpid(), it's
always safe, so override the tainting there.  Fixes [perl #109688].

1 files changed, 4 insertions, 1 deletions

diff --git a/mg.c b/mg.c
index f450d17000..8b30f93497 100644
--- a/mg.c
+++ b/mg.c
@@ -1079,9 +1079,12 @@ Perl_magic_get(pTHX_ SV *sv, MAGIC *mg)
     case '$': /* $$ */
 	{
 	    IV const pid = (IV)PerlProc_getpid();
-	    if (isGV(mg->mg_obj) || SvIV(mg->mg_obj) != pid)
+	    if (isGV(mg->mg_obj) || SvIV(mg->mg_obj) != pid) {
 		/* never set manually, or at least not since last fork */
 		sv_setiv(sv, pid);
+		/* never unsafe, even if reading in a tainted expression */
+		SvTAINTED_off(sv);
+	    }
 	    /* else a value has been assigned manually, so do nothing */
 	}
 	break;