linux-kernel - Re: [PATCH] tracing/histogram: Do not copy the fixed-size char array field over the field size

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Date:   Tue, 16 Nov 2021 14:01:52 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Beau Belgrave <beaub@...ux.microsoft.com>
Cc:     Masami Hiramatsu <mhiramat@...nel.org>,
        linux-kernel@...r.kernel.org, Namhyung Kim <namhyung@...nel.org>,
        Tom Zanussi <zanussi@...nel.org>
Subject: Re: [PATCH] tracing/histogram: Do not copy the fixed-size char
 array field over the field size

[ Resending to linux-kernel instead of ilinux-kernel ]

On Tue, 16 Nov 2021 13:34:31 -0500
Steven Rostedt <rostedt@...dmis.org> wrote:

> On Tue, 16 Nov 2021 09:53:59 -0800
> Beau Belgrave <beaub@...ux.microsoft.com> wrote:
> 
> > > @@ -3025,7 +3026,7 @@ static inline void __update_field_vars(struct tracing_map_elt *elt,
> > >  			char *str = elt_data->field_var_str[j++];
> > >  			char *val_str = (char *)(uintptr_t)var_val;
> > >  
> > > -			strscpy(str, val_str, STR_VAR_LEN_MAX);
> > > +			strscpy(str, val_str, val->size);    
> > 
> > Is it possible for val->size to be larger than STR_VAR_LEN_MAX?
> > field_var_str is alloc'd to be the size of STR_VAR_LEN_MAX (256).  
> 
> Yes.
> 
>   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=938aa33f14657c9ed9deea348b7d6f14b6d69cb7
> 
>  ;-)
> 
> -- Steve
> 
> >   
> > >  			var_val = (u64)(uintptr_t)str;
> > >  		}
> > >  		tracing_map_set_var(elt, var_idx, var_val);
> > > @@ -4920,7 +4921,7 @@ static void hist_trigger_elt_update(struct hist_trigger_data *hist_data,
> > >  
> > >  				str = elt_data->field_var_str[idx];
> > >  				val_str = (char *)(uintptr_t)hist_val;
> > > -				strscpy(str, val_str, STR_VAR_LEN_MAX);
> > > +				strscpy(str, val_str, hist_field->size);    
> > 
> > Same as above.  
>