[PATCH] setpgrp() should extend the stack before modifying it

[Niko Tyni]

As reported by Marcin Owsiany in <http://bugs.debian.org/512796>,
invoking setpgrp without any arguments could corrupt the stack.
---
 pp_sys.c            |    1 +
 t/op/setpgrpstack.t |   16 ++++++++++++++++
 2 files changed, 17 insertions(+), 0 deletions(-)
 create mode 100644 t/op/setpgrpstack.t

diff --git a/pp_sys.c b/pp_sys.c
index cfbf918..0d2c970 100644
--- a/pp_sys.c
+++ b/pp_sys.c
@@ -4318,6 +4318,7 @@ PP(pp_setpgrp)
     if (MAXARG < 2) {
 	pgrp = 0;
 	pid = 0;
+	XPUSHi(-1);
     }
     else {
 	pgrp = POPi;
diff --git a/t/op/setpgrpstack.t b/t/op/setpgrpstack.t
new file mode 100644
index 0000000..31f498e
--- /dev/null
+++ b/t/op/setpgrpstack.t
@@ -0,0 +1,16 @@
+#!./perl -w
+
+BEGIN {
+    chdir 't' if -d 't';
+    @INC = '../lib';
+    require './test.pl';
+}
+
+use Config;
+plan tests => 2;
+
+SKIP: {
+    skip "setpgrp() is not available", 2 unless $Config{d_setpgrp};
+    ok(!eval { package A;sub foo { die("got here") }; package main; A->foo(setpgrp())});
+    ok($@ =~ /got here/, "setpgrp() should extend the stack before modifying it");
+}
-- 
1.5.6.5


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