[PATCH] argp-help: Get rid of alloca.

[Joe Simmons-Talbott]

On Thu, Aug 03, 2023 at 09:11:37AM -0400, Joe Simmons-Talbott via Libc-alpha wrote:
> On Wed, Jul 12, 2023 at 01:02:06PM -0400, Joe Simmons-Talbott wrote:
> > Replace alloca with a scratch_buffer to avoid potential stack overflow.
> 
> Ping.
Ping.

Thanks,
Joe
> 
> Thanks,
> Joe
> > 
> > Checked on x86_64-linux-gnu
> > ---
> >  argp/argp-help.c | 26 +++++++++++++++++++++++---
> >  1 file changed, 23 insertions(+), 3 deletions(-)
> > 
> > diff --git a/argp/argp-help.c b/argp/argp-help.c
> > index d019ed58d2..a5982334f6 100644
> > --- a/argp/argp-help.c
> > +++ b/argp/argp-help.c
> > @@ -40,6 +40,7 @@ char *alloca ();
> >  # endif
> >  #endif
> >  
> > +#include <scratch_buffer.h>
> >  #include <stdbool.h>
> >  #include <stddef.h>
> >  #include <stdlib.h>
> > @@ -1450,8 +1451,17 @@ hol_usage (struct hol *hol, argp_fmtstream_t stream)
> >      {
> >        unsigned nentries;
> >        struct hol_entry *entry;
> > -      char *short_no_arg_opts = alloca (strlen (hol->short_options) + 1);
> > -      char *snao_end = short_no_arg_opts;
> > +      struct scratch_buffer buf;
> > +      scratch_buffer_init (&buf);
> > +      char *short_no_arg_opts;
> > +      char *snao_end;
> > +
> > +      if (!scratch_buffer_set_array_size (&buf, 1,
> > +					   strlen (hol->short_options) + 1))
> > +        return;
> > +      short_no_arg_opts = buf.data;
> > +      snao_end = short_no_arg_opts;
> > +	
> >  
> >        /* First we put a list of short options without arguments.  */
> >        for (entry = hol->entries, nentries = hol->num_entries
> > @@ -1478,6 +1488,8 @@ hol_usage (struct hol *hol, argp_fmtstream_t stream)
> >  	   ; entry++, nentries--)
> >  	hol_entry_long_iterate (entry, usage_long_opt,
> >  				entry->argp->argp_domain, stream);
> > +
> > +      scratch_buffer_free (&buf);
> >      }
> >  }
> >  
> > @@ -1698,7 +1710,13 @@ _help (const struct argp *argp, const struct argp_state *state, FILE *stream,
> >      {
> >        int first_pattern = 1, more_patterns;
> >        size_t num_pattern_levels = argp_args_levels (argp);
> > -      char *pattern_levels = alloca (num_pattern_levels);
> > +      struct scratch_buffer buf;
> > +      scratch_buffer_init (&buf);
> > +      char *pattern_levels;
> > +
> > +      if (!scratch_buffer_set_array_size (&buf, 1, num_pattern_levels))
> > +        return;
> > +      pattern_levels = buf.data;
> >  
> >        memset (pattern_levels, 0, num_pattern_levels);
> >  
> > @@ -1746,6 +1764,8 @@ _help (const struct argp *argp, const struct argp_state *state, FILE *stream,
> >  	  first_pattern = 0;
> >  	}
> >        while (more_patterns);
> > +
> > +      scratch_buffer_free (&buf);
> >      }
> >  
> >    if (flags & ARGP_HELP_PRE_DOC)
> > -- 
> > 2.39.2
> > 
>