On Wed, Jun 26, 2019 at 12:21:49PM -0400, J. Bruce Fields wrote: > On Mon, Jun 24, 2019 at 05:05:12PM -0400, J. Bruce Fields wrote: > > On Sat, Jun 22, 2019 at 01:22:56PM -0700, Kees Cook wrote: > > > On Sat, Jun 22, 2019 at 03:00:58PM -0400, J. Bruce Fields wrote: > > > > The logic around ESCAPE_NP and the "only" string is really confusing. I > > > > started assuming I could just add an ESCAPE_NONASCII flag and stick " > > > > and \ into the "only" string, but it doesn't work that way. > > > > > > Yeah, if ESCAPE_NP isn't specified, the "only" characters are passed > > > through. It'd be nice to have an "add" or a clearer way to do actual > > > ctype subsets, etc. If there isn't an obviously clear way to refactor > > > it, just skip it for now and I'm happy to ack your original patch. :) > > > > There may well be some simplification possible here.... There aren't > > really many users of "only", for example. I'll look into it some more. > > The printk users are kind of mysterious to me. I did a grep for > > git grep '%[0-9.*]pE' > > which got 75 hits. All of them for pE. I couldn't find any of the > other pE[achnops] variants. pE is equivalent to ESCAPE_ANY|ESCAPE_NP. > Confusingly, ESCAPE_NP doesn't mean "escape non-printable", it means > "don't escape printable". So things like carriage returns aren't > escaped. No, I was confused: "\n" is non-printable according to isprint(), so ESCAPE_ANY_NP *will* escape it. So this isn't quite so bad. SSIDs are usually printed as '%*pE', so arguably we should be escaping the single quote character too, but at least we're not allowing line breaks through. I don't know about non-ascii. > One of the hits outside wireless code was in drm_dp_cec_adap_status, > which was printing some device ID into a debugfs file with "ID: %*pE\n". > If the ID actually needs escaping, then I suspect the meant to escape \n > too to prevent misparsing that output. And same here, this is OK. --b.
