RE: [PHP-DEV] Problem with ext/libxml RINIT/RSHUTDOWN

BTW: libxml can be compiled with LIBXML_THREAD_ENABLED. Dmitry. > -----Original Message----- > From: Wez Furlong [mailto:kingwez@gmail.com] > Sent: Friday, March 17, 2006 4:33 PM > To: Rob Richards > Cc: Dmitry Stogov; internals@lists.php.net > Subject: Re: [PHP-DEV] Problem with ext/libxml RINIT/RSHUTDOWN > > > Sounds like a nasty situation. > I don't think it's possible to sanely restore the handlers at > rshutdown in a threaded build without screwing up the other > threads that are currently executing. > > My suggestion is to not restore the handlers for threaded > builds, and if there is a library sharing/abuse issue, then > treat it as an installation/configuration problem for the > person deploying it (eg: don't do that!). There's not much > you can do about that without rewriting libxml2 to not use > globals for the callbacks. :-/ > > --Wez. > > On 3/17/06, Rob Richards <rrichards@ctindustries.net> wrote: > > Dmitry Stogov wrote: > > > Hi Wez, > > > > > > I found a bad code in ext/libxml. > > > > > > On each request startup/shutdown it changing some libxml > callbacks. > > > At first this slowdown each request, at second multi-threaded PHP > > > may fail, because different threads may set/clean the > same callbacks > > > in the same time. > > > > > > May be it is possible to setup these callbacks forever in > > > MINIT/MSHUTDOWN, set some flag (somthing like > LIBXML(in_request)) in > > > RINIT/RSHUTDOWN, and check it in callbacks. > > > > > Which ones in particular? > > Each of the callbacks being utilized are thread safe. > > The reason why they need to be set per request is in order to play > > nice with any other modules that might be loaded and use libxml2. > > > > for example: prior to how the current callbacks are > implemented it was > > possible to blow away PHP stream usage by any of the xml extensions > > using mod_perl and its xsl module (could do this whether or not PHP > > was running threaded). There are also many other ways to screw with > > the libxml2 globals and effect PHP extensions based on > libxml2 as well > > using other modules so the only way to protect them is on each > > request. In short putting them into the MINIT/MSHUTDOWN will open > > security holes. > > > > Rob > > > >