Blob Blame Raw
From 85df897fcfe76250deecfdeb239ba1e4279d8532 Mon Sep 17 00:00:00 2001
From: David Mitchell <davem@iabyn.com>
Date: Tue, 26 Mar 2019 11:04:07 +0000
Subject: [PATCH] avoid leak with local $h{foo}, $a[n]
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

When SAVEt_DELETE / SAVEt_ADELETE deletes a hash/array entry on scope
exit, they also decrement the refcount of the hash/array, and for the
hash, also free the saved key.

However, if the call to hv_delete() or av_delete() dies (e.g. when
calling a tied DELETE method) then the hash/array and key will leak
because leave_scope() calls av/hv_delete(), *then* does the
SvREFCNT_dec() etc.

The fix is to push new FREEPV/FREESV actions just before calling
av/hv_delete().

Signed-off-by: Petr Písař <ppisar@redhat.com>
---
 scope.c    | 17 ++++++++++++++---
 t/op/tie.t | 37 +++++++++++++++++++++++++++++++++++++
 2 files changed, 51 insertions(+), 3 deletions(-)

diff --git a/scope.c b/scope.c
index 83a7b76893..3e4ee4344b 100644
--- a/scope.c
+++ b/scope.c
@@ -1253,15 +1253,26 @@ Perl_leave_scope(pTHX_ I32 base)
 
 	case SAVEt_DELETE:
             a0 = ap[0]; a1 = ap[1]; a2 = ap[2];
+            /* hv_delete could die, so free the key and SvREFCNT_dec the
+             * hv by pushing new save actions
+             */
+            /* ap[0] is the key */
+            ap[1].any_uv = SAVEt_FREEPV; /* was len */
+            /* ap[2] is the hv */
+            ap[3].any_uv = SAVEt_FREESV; /* was SAVEt_DELETE */
+            PL_savestack_ix += 4;
 	    (void)hv_delete(a2.any_hv, a0.any_pv, a1.any_i32, G_DISCARD);
-	    SvREFCNT_dec(a2.any_hv);
-	    Safefree(a0.any_ptr);
 	    break;
 
 	case SAVEt_ADELETE:
             a0 = ap[0]; a1 = ap[1];
+            /* av_delete could die, so SvREFCNT_dec the av by pushing a
+             * new save action
+             */
+            ap[0].any_av = a1.any_av;
+            ap[1].any_uv = SAVEt_FREESV;
+            PL_savestack_ix += 2;
 	    (void)av_delete(a1.any_av, a0.any_iv, G_DISCARD);
-	    SvREFCNT_dec(a1.any_av);
 	    break;
 
 	case SAVEt_DESTRUCTOR_X:
diff --git a/t/op/tie.t b/t/op/tie.t
index a2d771a009..bfcafce87a 100644
--- a/t/op/tie.t
+++ b/t/op/tie.t
@@ -1585,3 +1585,40 @@ print "[$x][$f][$n][$s]\n";
 EXPECT
 [3][1][3][0]
 [0][2][3][0]
+########
+# dying while doing a SAVEt_DELETE dureing scope exit leaked a copy of the
+# key. Give ASan something to play with
+sub TIEHASH { bless({}, $_[0]) }
+sub EXISTS { 0 }
+sub DELETE { die; }
+sub DESTROY { print "destroy\n"; }
+
+eval {
+    my %h;
+    tie %h, "main";
+    local $h{foo};
+    print "leaving\n";
+};
+print "left\n";
+EXPECT
+leaving
+destroy
+left
+########
+# ditto for SAVEt_DELETE with an array
+sub TIEARRAY { bless({}, $_[0]) }
+sub EXISTS { 0 }
+sub DELETE { die; }
+sub DESTROY { print "destroy\n"; }
+
+eval {
+    my @a;
+    tie @a, "main";
+    delete local $a[0];
+    print "leaving\n";
+};
+print "left\n";
+EXPECT
+leaving
+destroy
+left
-- 
2.20.1