From 75bb5aa48dfcf930533cd069393fc8a45e4ece18 Mon Sep 17 00:00:00 2001
From: David Mitchell <davem@iabyn.com>
Date: Fri, 22 Mar 2019 12:31:57 +0000
Subject: [PATCH] fix leak in cloned regexes.
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When a regex is cloned for a new thread, the string buffer (which holds
the text of the original pattern) wasn't being freed because SvLEN was
being set to 0.
For example:
use threads;
my $r = qr/abc/;
threads->new( sub { 1; })->join;
In the new thread, $r is cloned but when the thread exits, the string
buffer holding "(?^:abc)" was leaking.
This was broken by v5.27.2-30-gdf6b4bd565.
The problem was that in the cloned SV, the buffer was copied, but the
SvLEN(sv) was left set at zero, which along with the SVf_FAKE, mader it
look like the buffer was alien and so not freed.
SvLEN was 0 in the parent thread's $r, since $r and its compile-time
prototype share the same string buffer (so only the original SV has
SvLEN > 0 - all the copies - within the same thread - have mother_re
pointing to the original).
When REs are cloned into another thread, mother_re isn't preserved,
so each RE has its own copy of the buffer.
Signed-off-by: Petr Písař <ppisar@redhat.com>
---
regcomp.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/regcomp.c b/regcomp.c
index 547b9113e3..15783541a4 100644
--- a/regcomp.c
+++ b/regcomp.c
@@ -20956,6 +20956,11 @@ Perl_re_dup_guts(pTHX_ const REGEXP *sstr, REGEXP *dstr, CLONE_PARAMS *param)
2: something we no longer hold a reference on
so we need to copy it locally. */
RX_WRAPPED(dstr) = SAVEPVN(RX_WRAPPED_const(sstr), SvCUR(sstr)+1);
+ /* set malloced length to a non-zero value so it will be freed
+ * (otherwise in combination with SVf_FAKE it looks like an alien
+ * buffer). It doesn't have to be the actual malloced size, since it
+ * should never be grown */
+ SvLEN_set(dstr, SvCUR(sstr)+1);
ret->mother_re = NULL;
}
#endif /* PERL_IN_XSUB_RE */
--
2.20.1
