lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Message-ID: <Pine.LNX.4.64.0709301709490.19355@alien.or.mcafeemobile.com> Date: Sun, 30 Sep 2007 20:15:10 -0700 (PDT) From: Davide Libenzi <davidel@...ilserver.org> To: Denys Vlasenko <vda.linux@...glemail.com> cc: Ulrich Drepper <drepper@...hat.com>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Andrew Morton <akpm@...ux-foundation.org> Subject: Re: F_DUPFD_CLOEXEC implementation On Mon, 1 Oct 2007, Denys Vlasenko wrote: > My use case is: I want to do a nonblocking read on descriptor 0 (stdin). > It may be a pipe or a socket. > > There may be other processes which share this descriptor with me, > I simply cannot know that. And they, too, may want to do reads on it. > > I want to do nonblocking read in such a way that neither those other > processes will ever see fd switching to O_NONBLOCK and back, and > I also want to be safe from other processes doing the same. > > I don't see how this can be done using standard unix primitives. Indeed. You could simulate non-blocking using poll with zero timeout, but if another task may read/write on it, your following read/write may end up blocking even after a poll returned the required events. One way to solve this would be some sort of readx/writex where you pass an extra flags parameter (this could be done with sys_indirect, assuming we'll ever get that mainline) where you specify the non-blocking requirement for-this-call, and not as global per-file flag. Then, of course, you'll have to modify all the "file->f_flags & O_NONBLOCK" tests (and there are many of them) to check for that flag too (that can be a per task_struct flag). - Davide - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists