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Message-ID: <20160131162600.GW9621@port70.net>
Date: Sun, 31 Jan 2016 17:26:01 +0100
From: Szabolcs Nagy <nsz@...t70.net>
To: musl@...ts.openwall.com
Subject: Re: [PATCH] regex: increase the stack tre uses for tnfa
creation
* Khem Raj <raj.khem@...il.com> [2016-01-31 08:04:45 -0800]:
> On Sun, Jan 31, 2016 at 7:46 AM, Szabolcs Nagy <nsz@...t70.net> wrote:
> > 10k elements stack is increased to 1000k,
>
> It seems this stack is on heap is that right ?
> if not then does this enforce some higher minimum limit on stack
>
yes this is heap allocated buffer (but called and used as stack
in the tre code)
> otherwise tnfa creation fails
> > for reasonable sized patterns: a single literal char can add 7 elements
> > to this stack, so regcomp of an 1500 char long pattern (with only litral
> > chars) fails with REG_ESPACE. (the new limit allows about < 150k chars,
> > this arbitrary limit allows most command line regex usage.)
> >
> > ideally there would be no upper bound: regcomp dynamically reallocates
> > this buffer, every reallocation checks for allocation failure and at
> > the end this stack is freed so there is no reason for special bound.
> > however that may have unwanted effect on regcomp and regexec runtime
> > so this is a conservative change.
> > ---
> > src/regex/regcomp.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/src/regex/regcomp.c b/src/regex/regcomp.c
> > index 7ce2988..da6abd1 100644
> > --- a/src/regex/regcomp.c
> > +++ b/src/regex/regcomp.c
> > @@ -2688,7 +2688,7 @@ regcomp(regex_t *restrict preg, const char *restrict regex, int cflags)
> >
> > /* Allocate a stack used throughout the compilation process for various
> > purposes. */
> > - stack = tre_stack_new(512, 10240, 128);
> > + stack = tre_stack_new(512, 1024000, 128);
> > if (!stack)
> > return REG_ESPACE;
> > /* Allocate a fast memory allocator. */
> > --
> > 2.7.0
> >
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