Re: [igt-dev] [PATCH i-g-t 1/3] tests/testdisplay: fix heap overflow

["Ser, Simon" <simon.ser@intel.com>]

On Wed, 2019-03-20 at 11:22 +0000, Chris Wilson wrote:
> Quoting Simon Ser (2019-03-20 11:15:54)
> > Also simplify the code by using dirname(3).
> > 
> > Signed-off-by: Simon Ser <simon.ser@intel.com>
> > ---
> >  tests/testdisplay.c | 17 ++++-------------
> >  1 file changed, 4 insertions(+), 13 deletions(-)
> > 
> > diff --git a/tests/testdisplay.c b/tests/testdisplay.c
> > index b3657264..2b26ed1b 100644
> > --- a/tests/testdisplay.c
> > +++ b/tests/testdisplay.c
> > @@ -51,6 +51,7 @@
> >  #include <cairo.h>
> >  #include <errno.h>
> >  #include <getopt.h>
> > +#include <libgen.h>
> >  #include <math.h>
> >  #include <stdint.h>
> >  #include <stdbool.h>
> > @@ -563,24 +564,14 @@ static gboolean input_event(GIOChannel
> > *source, GIOCondition condition,
> >         return TRUE;
> >  }
> >  
> > -static void enter_exec_path( char **argv )
> > +static void enter_exec_path(char **argv)
> >  {
> > -       char *exec_path = NULL;
> > -       char *pos = NULL;
> > -       short len_path = 0;
> > +       char *exec_path;
> >         int ret;
> >  
> > -       len_path = strlen( argv[0] );
> > -       exec_path = (char*) malloc(len_path);
> > -
> > -       memcpy(exec_path, argv[0], len_path);
> > -       pos = strrchr(exec_path, '/');
> > -       if (pos != NULL)
> > -               *(pos+1) = '\0';
> > -
> > +       exec_path = dirname(argv[0]);
> 
> dirname() modifies inplace, so it might not be suitable as presumably
> we
> were copying the argv[0] for a reason :)
> 
> exec_path = strcpy(argv[0]);
> if (exec_path)
> 	exec_path = dirname(exec_path);
> igt_assert_eq(chdir(exec_path), 0);
> free(exec_path);
> 
> And if we are not allowed to modify argv, why not say so and make it
> const?

That's a good point. I thought dirname returned a pointer to statically
allocated memory, but as you said and per the spec libc is also allowed
to modify the argument in place.

Will send v2 shortly.

> -Chris
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