Re: [Qemu-devel] [PATCH] vl.c: fix memleaks with g_strdup+strtok

[Daniel P. Berrange]

On Wed, Mar 02, 2016 at 11:07:02AM +0000, Stefan Hajnoczi wrote:
> On Wed, Feb 24, 2016 at 10:22:14AM +0100, Quentin PEREZ wrote:
> > diff --git a/vl.c b/vl.c
> > index b87e292..9f6593a 100644
> > --- a/vl.c
> > +++ b/vl.c
> > @@ -1362,16 +1362,19 @@ static int add_semihosting_arg(void *opaque,
> >  static inline void semihosting_arg_fallback(const char *file, const char 
> > *cmd)
> >  {
> >      char *cmd_token;
> > +    char *dup_cmd;
> > 
> >      /* argv[0] */
> >      add_semihosting_arg(&semihosting, "arg", file, NULL);
> > 
> >      /* split -append and initialize argv[1..n] */
> > -    cmd_token = strtok(g_strdup(cmd), " ");
> > +    dup_cmd = g_strdup(cmd);
> > +    cmd_token = strtok(dup_cmd, " ");
> >      while (cmd_token) {
> >          add_semihosting_arg(&semihosting, "arg", cmd_token, NULL);
> >          cmd_token = strtok(NULL, " ");
> >      }
> > +    g_free(dup_cmd);
> 
> add_semihosting_arg() stashes the cmd_token pointer.  semihosting.argv[]
> points to freed memory if you add g_free(dup_cmd).
> 
> I suggest leaving the code as-is since the lifetime of the semihosting
> global variable spans the entire run-time of the QEMU process.  It's not
> pretty but the leak is harmless.
> 
> If you really want to fix it you may need to add a semihosting_cleanup()
> function to free strings.

If fixing it I'd probably suggest using g_strsplit() instead of
strdup+strtok too, as it accepts a const string & returns allocated
strings which is a nicer contract that strtok which modifies its arg

Regards,
Daniel
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