linux/fs/notify
Heinrich Schuchardt 48149e9d3a fanotify: check file flags passed in fanotify_init
Without this patch fanotify_init does not validate the value passed in
event_f_flags.

When a fanotify event is read from the fanotify file descriptor a new
file descriptor is created where file.f_flags = event_f_flags.

Internal and external open flags are stored together in field f_flags of
struct file.  Hence, an application might create file descriptors with
internal flags like FMODE_EXEC, FMODE_NOCMTIME set.

Jan Kara and Eric Paris both aggreed that this is a bug and the value of
event_f_flags should be checked:
  https://lkml.org/lkml/2014/4/29/522
  https://lkml.org/lkml/2014/4/29/539

This updated patch version considers the comments by Michael Kerrisk in
  https://lkml.org/lkml/2014/5/4/10

With the patch the value of event_f_flags is checked.
When specifying an invalid value error EINVAL is returned.

Internal flags are disallowed.

File creation flags are disallowed:
O_CREAT, O_DIRECTORY, O_EXCL, O_NOCTTY, O_NOFOLLOW, O_TRUNC, and O_TTY_INIT.

Flags which do not make sense with fanotify are disallowed:
__O_TMPFILE, O_PATH, FASYNC, and O_DIRECT.

This leaves us with the following allowed values:

O_RDONLY, O_WRONLY, O_RDWR are basic functionality. The are stored in the
bits given by O_ACCMODE.

O_APPEND is working as expected. The value might be useful in a logging
application which appends the current status each time the log is opened.

O_LARGEFILE is needed for files exceeding 4GB on 32bit systems.

O_NONBLOCK may be useful when monitoring slow devices like tapes.

O_NDELAY is equal to O_NONBLOCK except for platform parisc.
To avoid code breaking on parisc either both flags should be
allowed or none. The patch allows both.

__O_SYNC and O_DSYNC may be used to avoid data loss on power disruption.

O_NOATIME may be useful to reduce disk activity.

O_CLOEXEC may be useful, if separate processes shall be used to scan files.

Once this patch is accepted, the fanotify_init.2 manpage has to be updated.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Valdis Kletnieks <Valdis.Kletnieks@vt.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-06-04 16:53:52 -07:00
..
dnotify inotify: Fix reporting of cookies for inotify events 2014-02-18 11:17:17 +01:00
fanotify fanotify: check file flags passed in fanotify_init 2014-06-04 16:53:52 -07:00
inotify fsnotify: Allocate overflow events with proper type 2014-02-25 11:18:06 +01:00
fdinfo.c Merge branch 'for-next' of git://git.infradead.org/users/eparis/notify 2012-12-20 20:11:52 -08:00
fdinfo.h fs, notify: add procfs fdinfo helper 2012-12-17 17:15:28 -08:00
fsnotify.c inotify: Fix reporting of cookies for inotify events 2014-02-18 11:17:17 +01:00
fsnotify.h fsnotify: remove global fsnotify groups lists 2010-07-28 10:18:54 -04:00
group.c fsnotify: Allocate overflow events with proper type 2014-02-25 11:18:06 +01:00
inode_mark.c hlist: drop the node parameter from iterators 2013-02-27 19:10:24 -08:00
Kconfig fanotify: allow fanotify to be built 2010-10-28 17:22:13 -04:00
Makefile fs, notify: add procfs fdinfo helper 2012-12-17 17:15:28 -08:00
mark.c fs/notify/mark.c: trivial cleanup 2014-06-04 16:53:52 -07:00
notification.c fsnotify: Allocate overflow events with proper type 2014-02-25 11:18:06 +01:00
vfsmount_mark.c hlist: drop the node parameter from iterators 2013-02-27 19:10:24 -08:00