Re: [PATCH 3/3] tracing/filters: Support filtering for char * strings

[Steven Rostedt <rostedt@goodmis.org>]

On Fri, 7 Aug 2009, Li Zefan wrote:
> > 
> > What protection is this giving us?
> > 
> 
> __field(char *) suggests it should be treated as plain pointer,
> while __field_ext(char *, FILTER_PTR_STR) suggests he's aware it's
> safe to dereference the pointer, for example the case in Frederic's
> blk events.
> 
> In Frederic's initial version, "char *" field will always be
> attached to ptr_str filter function. This is unsafe, because for
> other fields defined as "char *" but not safe to dereference,
> a user still can do this:
> 
> 	# echo 'name == abc' > filter
> 
> Then we'll deref a pointer that can point to unsafe data.
> 
> In this patch, this won't happen, as long as the developer is
> aware that his use of __field_ext(char *) is right.
> 
> Otherwise, he will just use normal __field(char *) and print
> the pointer itself in TP_printk().

Ah, so the answer I'm looking for is:

The filtering will not dereference "char *" unless the developer 
explicitly sets FILTER_PTR_STR in __field_ext.

Is this above statement correct?

-- Steve