Re: [PATCH v3] argp-help: Get rid of alloca.

[Joe Simmons-Talbott <josimmon@redhat.com>]

On Wed, Sep 13, 2023 at 04:45:21PM -0300, Adhemerval Zanella Netto wrote:
> 
> 
> On 13/09/23 13:00, Joe Simmons-Talbott wrote:
> > Replace alloca with malloc and a scratch_buffer to avoid potential stack
> > overflow.
> > 
> > Checked on x86_64-linux-gnu
> > ---
> >  argp/argp-help.c | 40 ++++++++++++++++++++++------------------
> >  1 file changed, 22 insertions(+), 18 deletions(-)
> > 
> > diff --git a/argp/argp-help.c b/argp/argp-help.c
> > index d019ed58d2..54a15a8233 100644
> > --- a/argp/argp-help.c
> > +++ b/argp/argp-help.c
> > @@ -25,21 +25,7 @@
> >  #include <config.h>
> >  #endif
> >  
> > -/* AIX requires this to be the first thing in the file.  */
> > -#ifndef __GNUC__
> > -# if HAVE_ALLOCA_H || defined _LIBC
> > -#  include <alloca.h>
> > -# else
> > -#  ifdef _AIX
> > -#pragma alloca
> > -#  else
> > -#   ifndef alloca /* predefined by HP cc +Olibcalls */
> > -char *alloca ();
> > -#   endif
> > -#  endif
> > -# endif
> > -#endif
> > -
> > +#include <scratch_buffer.h>
> >  #include <stdbool.h>
> >  #include <stddef.h>
> >  #include <stdlib.h>
> > @@ -1450,8 +1436,14 @@ 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;
> > +      char *short_no_arg_opts;
> > +      char *snao_end;
> > +
> > +      short_no_arg_opts = malloc (strlen (hol->short_options) + 1);
> > +      assert (short_no_arg_opts != NULL);
> > +
> > +      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 +1470,8 @@ hol_usage (struct hol *hol, argp_fmtstream_t stream)
> >  	   ; entry++, nentries--)
> >  	hol_entry_long_iterate (entry, usage_long_opt,
> >  				entry->argp->argp_domain, stream);
> > +
> > +      free (short_no_arg_opts);
> >      }
> >  }
> >  \f
> > @@ -1698,7 +1692,15 @@ _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;
> > +      bool result;
> > +
> > +      result = scratch_buffer_set_array_size (&buf, 1, num_pattern_levels);
> > +      assert (result);
> > +
> > +      pattern_levels = buf.data;
> >  
> >        memset (pattern_levels, 0, num_pattern_levels);
> >  
> 
> 
> Use malloc here as well.

Done in v4.