Recursion in as_info_where

[Alan Modra]

On Wed, Feb 01, 2023 at 10:24:25AM +0100, Jan Beulich wrote:
> On 01.02.2023 07:36, Alan Modra via Binutils wrote:
> > This function has a gas_assert, ie. possible call to as_abort, which
> > calls as_report_context, which calls as_info_where.  Attached fuzzer
> > testcase managed to trigger a stack overflow.
> > 
> > 	* messages.c (as_info_where): Don't gas_assert.
> > 
> > diff --git a/gas/messages.c b/gas/messages.c
> > index 0db075d779c..7c018acf69f 100644
> > --- a/gas/messages.c
> > +++ b/gas/messages.c
> > @@ -141,8 +141,6 @@ as_info_where (const char *file, unsigned int line, unsigned int indent,
> >    va_list args;
> >    char buffer[2000];
> >  
> > -  gas_assert (file != NULL && line > 0 && indent <= INT_MAX);
> 
> If this go in the way, isn't it that the assertion actually triggered?
> In which case shouldn't the cause for it triggering be addressed
> instead, to avoid subsequent knock-on damage (e.g. from de-referencing
> "file"? (I may want to play with the testcase a little myself.)

The testcase is really weird, something that no programmer would ever
write.  It failed the assert with line == 0.  I'll let you discover
the horrible "# line file" with embedded \0 that gets you there.  :-)
I'm not motivated to fix that sort of insanity.

-- 
Alan Modra
Australia Development Lab, IBM