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Re: RFA: libiberty: Add a limit on demangling qualifiers (PR 87241)
- From: Jason Merrill <jason at redhat dot com>
- To: Nick Clifton <nickc at redhat dot com>
- Cc: Ian Lance Taylor <ian at airs dot com>, gcc-patches List <gcc-patches at gcc dot gnu dot org>, redi at gcc dot gnu dot org
- Date: Wed, 12 Dec 2018 15:30:10 -0500
- Subject: Re: RFA: libiberty: Add a limit on demangling qualifiers (PR 87241)
- References: <email@example.com>
On Wed, Dec 12, 2018 at 6:29 AM Nick Clifton <firstname.lastname@example.org> wrote:
> Sorry to bother you, but I have another libiberty demangler resource
> exhaustion prevention patch to present. This one is for:
> Jonathan Wakely reported that __cxa_demanlge() was returning a -2
> result, but I did not see this. Instead I found that
> consume_count_with_underscores() is returning a very large number
> (because a very large value is encoded in the mangled string) and this
> is resulting in many calls to remember_Ktype() which eventually
> exhaust the amount of memory available.
> The attached patch is a simplistic approach to solving this problem by
> adding a hard upper limit on the number of qualifiers that will be
> allowed by the demangler. I am not sure if this is the best approach
> to solving the problem, but it is a simple one, and I would think one
> that would not prevent the demangling of any real mangled names. The
> limit does not have to be DEMANGLE_RECURSE_LIMIT of course. I just
> chose that value because it was convenient and of a size that I
> thought was appropriate.
> I also did run the libiberty testsuite this time, with no failures
> reported. :-)
> OK to apply ?
> 2018-12-12 Nick Clifton <email@example.com>
> * cplus-dem.c (demangle_qualified): Add an upper limit on the
> number of qualifiers supported, based upon the value of
This issue also will be resolved by disabling or removing the old
demangling code, which I haven't seen anyone argue against.