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From 28eabf1185634216ca335b3a24e1131b0f392ca1 Mon Sep 17 00:00:00 2001
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From: David Mitchell <davem@iabyn.com>
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Date: Wed, 10 Jul 2019 12:59:06 +0100
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Subject: [PATCH] avoid SEGV with uninit warning with multideref
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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RT #134275
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When the 'uninitialized warning' code in S_find_uninit_var() comes
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across an OP_MULTIDEREF node, it scans it to see if any part of that op
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(e.g. the indices or the returned value) could have been the source of
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the uninitialized value which triggered the warning. Unfortunately when
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getting an AV or HV from a GV, it wasn't checking whether gp_av/gp_hv
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contained a NULL value. If so, it would SEGV.
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The test code is a bit contrived; you have to "pull the rug" from under
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the GV at just the right moment with *foo = *bar, then trigger an uninit
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warning on an op whose subtree includes an OP_MULTIDEREF.
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Signed-off-by: Petr Písař <ppisar@redhat.com>
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---
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sv.c | 5 ++++-
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t/lib/warnings/9uninit | 10 ++++++++++
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2 files changed, 14 insertions(+), 1 deletion(-)
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diff --git a/sv.c b/sv.c
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index 83de536ad7..4315fe9b64 100644
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--- a/sv.c
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+++ b/sv.c
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@@ -16662,8 +16662,11 @@ S_find_uninit_var(pTHX_ const OP *const obase, const SV *const uninit_sv,
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if (agg_targ)
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sv = PAD_SV(agg_targ);
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- else if (agg_gv)
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+ else if (agg_gv) {
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sv = is_hv ? MUTABLE_SV(GvHV(agg_gv)) : MUTABLE_SV(GvAV(agg_gv));
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+ if (!sv)
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+ break;
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+ }
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else
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break;
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diff --git a/t/lib/warnings/9uninit b/t/lib/warnings/9uninit
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index 774c6ee432..5c173fdb2a 100644
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--- a/t/lib/warnings/9uninit
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+++ b/t/lib/warnings/9uninit
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@@ -2206,3 +2206,13 @@ use warnings 'uninitialized';
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undef $0;
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EXPECT
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Use of uninitialized value in undef operator at - line 5.
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+########
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+# RT #134275
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+# This was SEGVing due to the multideref code in S_find_uninit_var not
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+# handling a GV with a null gp_hv slot.
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+use warnings 'uninitialized';
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+"" =~ /$foo{a}${*foo=*bar}$x/;
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+EXPECT
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+Use of uninitialized value in regexp compilation at - line 5.
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+Use of uninitialized value in regexp compilation at - line 5.
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+Use of uninitialized value $x in regexp compilation at - line 5.
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--
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2.20.1
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