On Wed, 2013-09-11 at 11:19 -0700, Kees Cook wrote: > On Wed, Sep 11, 2013 at 2:31 AM, Dan Carpenter <dan.carpenter@xxxxxxxxxx> wrote: > > On Tue, Sep 10, 2013 at 10:19:17PM -0700, Kees Cook wrote: > >> In the former case, format characters will get processed by the > >> sprintf logic. In the latter, they are printed as-is. In this specific > >> case, if there was a way to inject strings like "ohai %n" into the > >> msgbuf string, the former would actually attempt to resolve the %n. In > >> the simple case, this could lead to Oopses, and in the unlucky case, > >> it could allow arbitrary memory writing and execution control. > >> > >> http://en.wikipedia.org/wiki/Uncontrolled_format_string > > > > The kernel ignores %n so hopefully it can't actually write to memory. > > I wish! This is not the case, though. See FORMAT_TYPE_NRCHARS in > lib/vsprintf.c's vsnprintf(). > > $ git grep '%n' | wc -l > 111 Umm. See: lib/vsprintf.c /** * vsnprintf - Format a string and place it in a buffer [...] * %n is ignored %n does work for vsscanf though. _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
