Messages in this thread Patch in this message | | | From | Yann Droneaud <> | Subject | [PATCHv8.1] fanotify: enable close-on-exec on events' fd when requested in fanotify_init() | Date | Mon, 29 Sep 2014 10:49:15 +0200 |
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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)
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_init() 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 when requested.
[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.1394532336.git.ydroneaud@opteya.com Cc: Heinrich Schuchardt <xypron.glpk@gmx.de> Cc: Jan Kara <jack@suse.cz> Cc: Valdis Kletnieks <Valdis.Kletnieks@vt.edu> Cc: Michael Kerrisk-manpages <mtk.manpages@gmail.com> Cc: Lino Sanfilippo <LinoSanfilippo@gmx.de> Cc: Richard Guy Briggs <rgb@redhat.com> Cc: Eric Paris <eparis@redhat.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: stable@vger.kernel.org Cc: linux-api@vger.kernel.org Reviewed by: Heinrich Schuchardt <xypron.glpk@gmx.de> Signed-off-by: Yann Droneaud <ydroneaud@opteya.com> --- Hi Andrew and Henrich,
Please find an updated patch with a commit message fixed regarding the obsolote comments on code which is now updated, thanks to Heinrich's patch.
Changes from v8: - fixed commit message - added Reviewed-by:
Regards.
Yann Droneaud, OPTEYA
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 b13992a41bd9..c991616acca9 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
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