According to commit 80af258867648, file descriptor 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(). More, there's no effective check on event_f_flags value that would catch unknown / unsupported values, unlike the one on f_flags argument of the syscall (see FAN_ALL_INIT_FLAGS in include/uapi/linux/fanotify.h). Reading article "Botching up ioctls"[1] by Daniel Vetter might make one feel uncomfortable when trying to add extension to an API that doesn't check for unrecognized values. 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) Lookup also returned some wrong usage of the syscall: - in Gonk HAL from Mozilla Firefox OS sources[6]: mFd = fanotify_init(FAN_CLASS_NOTIF, FAN_CLOEXEC); Adding support for O_CLOEXEC in fanotify won't magically enable it for Gonk since FAN_CLOEXEC is defined as 0x1, which is likely equal to O_WRONLY when used in open flag context. In the other hand, it won't hurt it either. So this patch replaces call to macro get_unused_fd() by a call to function get_unused_fd_flags() with event_f_flags value as argument. This way O_CLOEXEC flag in the second argument of fanotify_init(2) syscall is interpreted so that close-on-exec get enabled. [1] http://blog.ffwll.ch/2013/11/botching-up-ioctls.html [2] http://cgit.freedesktop.org/systemd/systemd/tree/src/readahead/readahead-collect.c?id=v208#n294 [3] https://github.com/xaionaro/clsync/blob/v0.2.1/sync.c#L1631 https://github.com/xaionaro/clsync/blob/v0.2.1/configuration.h#L38 [4] http://www.lanedo.com/~aleksander/fanotify/fanotify-example.c [5] http://www.lanedo.com/2013/filesystem-monitoring-linux-kernel/ [6] http://hg.mozilla.org/mozilla-central/file/325c74addeba/hal/gonk/GonkDiskSpaceWatcher.cpp#l167 Link: http://lkml.kernel.org/r/cover.1401630396.git.ydroneaud@xxxxxxxxxx Cc: Richard Guy Briggs <rgb@xxxxxxxxxx> Cc: Eric Paris <eparis@xxxxxxxxxx> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Yann Droneaud <ydroneaud@xxxxxxxxxx> --- fs/notify/fanotify/fanotify_user.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c index 3fdc8a3e1134..6782226e2868 100644 --- a/fs/notify/fanotify/fanotify_user.c +++ b/fs/notify/fanotify/fanotify_user.c @@ -78,7 +78,7 @@ static int create_fd(struct fsnotify_group *group, pr_debug("%s: group=%p event=%p\n", __func__, group, event); - client_fd = get_unused_fd(); + client_fd = get_unused_fd_flags(group->fanotify_data.f_flags); if (client_fd < 0) return client_fd; -- 1.9.3 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html