Messages in this thread | | | From | Yann Droneaud <> | Date | Thu, 02 Oct 2014 08:20:55 +0200 | Subject | Re: [PATCHv8.1] fanotify: enable close-on-exec on events' fd when requested in fanotify_init() |
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Hi,
Le mercredi 01 octobre 2014 à 15:36 -0700, Andrew Morton a écrit : > On Mon, 29 Sep 2014 10:49:15 +0200 Yann Droneaud <ydroneaud@opteya.com> wrote: > > > According to commit 80af258867648 ('fanotify: groups can specify > > their f_flags for new fd'), file descriptors created as part of > > file access notification events inherit flags from the > > event_f_flags argument passed to syscall fanotify_init(2). > > > > So while it is legal for userspace to call fanotify_init() with > > O_CLOEXEC as part of its second argument, O_CLOEXEC is currently > > silently ignored. > > > > Indeed event_f_flags are only given to dentry_open(), which only > > seems to care about O_ACCMODE and O_PATH in do_dentry_open(), > > O_DIRECT in open_check_o_direct() and O_LARGEFILE in > > generic_file_open(). > > > > But it seems logical to set close-on-exec flag on the file > > descriptor if userspace is allowed to request it with O_CLOEXEC. > > > > In fact, according to some lookup on http://codesearch.debian.net/ > > and various search engine, there's already some userspace code > > requesting it: > > > > - in systemd's readahead[2]: > > > > fanotify_fd = fanotify_init(FAN_CLOEXEC|FAN_NONBLOCK, O_RDONLY|O_LARGEFILE|O_CLOEXEC|O_NOATIME); > > > > - in clsync[3]: > > > > #define FANOTIFY_EVFLAGS (O_LARGEFILE|O_RDONLY|O_CLOEXEC) > > > > int fanotify_d = fanotify_init(FANOTIFY_FLAGS, FANOTIFY_EVFLAGS); > > > > - in examples [4] from "Filesystem monitoring in the Linux > > kernel" article[5] by Aleksander Morgado: > > > > if ((fanotify_fd = fanotify_init (FAN_CLOEXEC, > > O_RDONLY | O_CLOEXEC | O_LARGEFILE)) < 0) > > So we have a number of apps which are setting O_CLOEXEC, but it doesn't > actually work. With this change it *will* work, so the behaviour of > those apps might change, possibly breaking them? >
In the other hand, not enabling close-on-exec might expose unwanted file descriptor to childs, creating security issues. YMMV.
-- Yann Droneaud OPTEYA
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