[PATCH] Sanitize printf functions

[Evgeniy Stepanov]

================
Comment at: lib/sanitizer_common/sanitizer_common_interceptors.inc:697
@@ +696,3 @@
+      va_copy(ar, ap);                                                         \
+      int size = REAL(vname2)(str, 0, format, ar);                             \
+      if (size >= 0) {                                                         \
----------------
Yury Gribov wrote:
> Evgeniy Stepanov wrote:
> > Yury Gribov wrote:
> > > Evgeniy Stepanov wrote:
> > > > Unless I'm missing something, you could use REAL(strlen)(str) here instead of calling *printf twice.
> > > Hm but str isn't necessarily a string - it's just plain array of chars. I don't think we can call strlen on it.
> > I think *printf always end the output with a null character, and never print null in the middle, but I don't see a clear indication of that in the spec.
> Sorry, I must be missing something... My intent with REAL(vname2) (which is actually REAL(vsnprintf)) is to estimate number of chars that will be written. 0 tells vsnprintf that it should not _write_ anything, only estimate number of chars. We could simply pass NULL instead of str and it wouldn't change anything. So why do you bother about str?
I'm just worried that it makes *printf quite a bit heavier - we now parse the format string 3 times (2 in libc *printf and 1 in our code). Alternatively, we could do 1 + 1, and then figure out the length of the resulting string with strlen() after the REAL *printf.



http://llvm-reviews.chandlerc.com/D2480