From: Peter Stephenson <p.stephenson@samsung.com>
To: zsh-workers@zsh.org
Subject: Re: infinite recursion in ihungetc()
Date: Wed, 22 Jul 2015 14:38:03 +0100 [thread overview]
Message-ID: <20150722143803.1be07f1e@pwslap01u.europe.root.pri> (raw)
In-Reply-To: <2874073.clZcYqQZLr@kdudka.brq.redhat.com>
On Wed, 22 Jul 2015 13:45:06 +0200
Kamil Dudka <kdudka@redhat.com> wrote:
> Fedora Analysis Framework captured 10 crashes of zsh-5.0.8 due to infinite
> recursion in ihungetc():
>
> https://retrace.fedoraproject.org/faf/reports/717794/
>
> The infinite recursion happens at this line:
>
> http://repo.or.cz/w/zsh/mirror.git/blob/a0862f63:/Src/hist.c#l908
>
> The 'hungetc' code pointer is obviously set to ihungetc() itself. We do
> not have full bakctrace of the crash but shouldn't there be any condition
> to actually stop the recursion when the conditions at lines 906-907 are
> true and hungetc points at ihungetc()?
>
> There is no single command that could invalidate any of the conditions
> after nesting deeper into the recursion...
Yes, it should be straightforward to prevent, although this code isn't
particularly transparent (or new), so I don't know how you could get
there.
pws
diff --git a/Src/hist.c b/Src/hist.c
index 6725313..cf224cb 100644
--- a/Src/hist.c
+++ b/Src/hist.c
@@ -136,6 +136,7 @@ mod_export int hist_skip_flags;
#define HA_NOINC (1<<1) /* Don't store, curhist not incremented */
#define HA_INWORD (1<<2) /* We're inside a word, don't add
start and end markers */
+#define HA_UNGET (1<<3) /* Recursively ungetting */
/* Array of word beginnings and endings in current history line. */
@@ -904,8 +905,13 @@ ihungetc(int c)
while (!lexstop && !errflag) {
if (hptr[-1] != (char) c && stophist < 4 &&
- hptr > chline + 1 && hptr[-1] == '\n' && hptr[-2] == '\\')
- hungetc('\n'), hungetc('\\');
+ hptr > chline + 1 && hptr[-1] == '\n' && hptr[-2] == '\\' &&
+ !(histactive & HA_UNGET)) {
+ histactive |= HA_UNGET;
+ hungetc('\n');
+ hungetc('\\');
+ histactive &= ~HA_UNGET;
+ }
if (expanding) {
zlemetacs--;
next prev parent reply other threads:[~2015-07-22 13:48 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-22 11:45 Kamil Dudka
2015-07-22 13:38 ` Peter Stephenson [this message]
2015-07-22 14:00 ` Kamil Dudka
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