Hi Bruno, On Apr 17 20:44, Bruno Haible via Cygwin wrote: > Hi Corinna, > > > > Would it be possible to change Cygwin's posix_spawnp implementation, > > > so that both tests succeed? > > > > Basically, yes, but... > > Thanks! > > > > Disclaimer: I have done my tests with Cygwin 2.9.0; so, if things have > > ^^^^^^^^^^^^ > > 2017-09-07 > > > > I'm a bit puzzled. You quote that only Cygwin 3.1.7 has the fixed > > posix_spawn, but then you test this with a version three years older? > > I have now verified that the findings with Cygwin 3.4.6 are the same as > with Cygwin 2.9.0. I had expected that, based on browsing through the > Cygwin git history; I confirm it now.
Thanks a lot! The patch is actually simple. But I'm not *that* happy with the change yet, for two reasons. First, the security risk outlined in https://sourceware.org/bugzilla/show_bug.cgi?id=13134#c0 doesn't actually exist on Cygwin, because we don't implement setuid/setgid executables. You can set the mode bits, but they are not acted upon. Second, the rational section in POSIX explains posix_spawn and posix_spawnp, but it does *not* actually provide an example implementation of posix_spawnp, only of posix_spawn. From the above bugzilla entry I take it that on glibc, both functions tried to run the shell if the executable isn't recognized (up to commits d96de9634a33 / 13adfa34aff). However, on Cygwin, only posix_spawnp does that,but not posix_spawn. In fact, I read the POSIX descriptions in terms of these functions quite thoroughly, and at no point I see it mentioned that posix_spawnp shall *not* work like exevlp/execvp. The crucial difference between posix_spawn and posixc_spawnp is described in an interestingly vague way: posix_spawnp() interprets the second parameter more elaborately than posix_spawn(). If I missed the point in the POSIX docs, please tell me. So, again, the patch is simple. But it's kind of a pity that the change in glibc has been made without a bigger discussion. Right now, it looks like the glibc change to posix_spawn was correct, but the change to posix_spawnp was arbitrary. Has anybody attempted to ask the Austin group to define this behaviour in posix_spawnp more concise? Is there a protocel from the Austin group? If not, wouldn't it be time to ask the Austin group? > Btw, there are two more functions in the posix_spawn family meanwhile: > * posix_spawn_file_actions_addchdir_np > implemented by glibc [1], musl libc, macOS, FreeBSD [2], Solaris ≥ 11.3 > used by a few packages (Firefox, Chromium, Rust) > * posix_spawn_file_actions_addfchdir_np > implemented in glibc, musl libc > but not used by any package so far [3]. > > The next POSIX will contain these functions (without the _np suffix).[4] Thanks for the pointers. I'm not sure I'll have the time to implement them soon, but I put them on my list for 3.5.0. Patches welcome! Thanks, Corinna -- Problem reports: https://cygwin.com/problems.html FAQ: https://cygwin.com/faq/ Documentation: https://cygwin.com/docs.html Unsubscribe info: https://cygwin.com/ml/#unsubscribe-simple
