Messages in this thread | | | Date | Fri, 07 Aug 2009 11:24:27 +0800 | From | Li Zefan <> | Subject | Re: [PATCH 3/3] tracing/filters: Support filtering for char * strings |
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Steven Rostedt wrote: > 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? >
Exactly. Sorry that I didn't explain it clearly in the first place. :)
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