When an fanotify listener is closing it may cause a deadlock between the
listener and the original task doing an fs operation.  If the original task
is waiting for a permissions response it will be holding the srcu lock.  The
listener cannot clean up and exit until after that srcu lock is syncronized.
Thus deadlock.  The fix introduced here is to stop accepting new permissions
events when a listener is shutting down and to grant permission for all
outstanding events.  Thus the original task will eventually release the srcu
lock and the listener can complete shutdown.
Reported-by: NAndreas Gruenbacher <agruen@suse.de>
Cc: Andreas Gruenbacher <agruen@suse.de>
Signed-off-by: NEric Paris <eparis@redhat.com>

This reverts commit 3bcf3860 (and the
accompanying commit c1e5c954 "vfs/fsnotify: fsnotify_close can delay
the final work in fput" that was a horribly ugly hack to make it work at
all).

The 'struct file' approach not only causes that disgusting hack, it
somehow breaks pulseaudio, probably due to some other subtlety with
f_count handling.

Fix up various conflicts due to later fsnotify work.
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

fanotify currently, when given a vfsmount_mark will look up (if it exists)
the corresponding inode mark.  This patch drops that lookup and uses the
mark provided.
Signed-off-by: NEric Paris <eparis@redhat.com>

should_send_event() and handle_event() will both need to look up the inode
event if they get a vfsmount event.  Lets just pass both at the same time
since we have them both after walking the lists in lockstep.
Signed-off-by: NEric Paris <eparis@redhat.com>

The global fsnotify groups lists were invented as a way to increase the
performance of fsnotify by shortcutting events which were not interesting.
With the changes to walk the object lists rather than global groups lists
these shortcuts are not useful.
Signed-off-by: NEric Paris <eparis@redhat.com>

group->mask is now useless.  It was originally a shortcut for fsnotify to
save on performance.  These checks are now redundant, so we remove them.
Signed-off-by: NEric Paris <eparis@redhat.com>

Because we walk the object->fsnotify_marks list instead of the global
fsnotify groups list we don't need the fsnotify_inode_mask and
fsnotify_vfsmount_mask as these were simply shortcuts in fsnotify() for
performance.  They are now extra checks, rip them out.
Signed-off-by: NEric Paris <eparis@redhat.com>

With the change of fsnotify to use srcu walking the marks list instead of
walking the global groups list we now know the mark in question.  The code can
send the mark to the group's handling functions and the groups won't have to
find those marks themselves.
Signed-off-by: NEric Paris <eparis@redhat.com>

Currently reading the inode->i_fsnotify_marks or
vfsmount->mnt_fsnotify_marks lists are protected by a spinlock on both the
read and the write side.  This patch protects the read side of those lists
with a new single srcu.
Signed-off-by: NEric Paris <eparis@redhat.com>

Currently fsnotify check is mark->group is NULL to decide if
fsnotify_destroy_mark() has already been called or not.  With the upcoming
rcu work it is a heck of a lot easier to use an explicit flag than worry
about group being set to NULL.
Signed-off-by: NEric Paris <eparis@redhat.com>

Al explains that calling dentry_open() with a mnt/dentry pair is only
garunteed to be safe if they are already used in an open struct file.  To
make sure this is the case don't store and use a struct path in fsnotify,
always use a struct file.
Signed-off-by: NEric Paris <eparis@redhat.com>

Rather than the horrific void ** argument and such just to pass the
fanotify_merge event back to the caller of fsnotify_add_notify_event() have
those things return an event if it was different than the event suggusted to
be added.
Signed-off-by: NEric Paris <eparis@redhat.com>

Currently fanotify fds opened for thier listeners are done with f_flags
equal to O_RDONLY | O_LARGEFILE.  This patch instead takes f_flags from the
fanotify_init syscall and uses those when opening files in the context of
the listener.
Signed-off-by: NEric Paris <eparis@redhat.com>

This patch adds a check to make sure that all fsnotify bits are unique and we
cannot accidentally use the same bit for 2 different fsnotify event types.
Signed-off-by: NEric Paris <eparis@redhat.com>

An inotify watch on a directory will send events for children even if those
children have been unlinked.  This patch add a new inotify flag IN_EXCL_UNLINK
which allows a watch to specificy they don't care about unlinked children.
This should fix performance problems seen by tasks which add a watch to
/tmp and then are overrun with events when other processes are reading and
writing to unlinked files they created in /tmp.

https://bugzilla.kernel.org/show_bug.cgi?id=16296Requested-by: NMatthias Clasen <mclasen@redhat.com>
Signed-off-by: NEric Paris <eparis@redhat.com>

The priority argument in fanotify is useless.  Kill it.
Signed-off-by: NEric Paris <eparis@redhat.com>

This is the backend work needed for fanotify to support the new
FS_OPEN_PERM and FS_ACCESS_PERM fsnotify events.  This is done using the
new fsnotify secondary queue.  No userspace interface is provided actually
respond to or request these events.
Signed-off-by: NEric Paris <eparis@redhat.com>

introduce a new fsnotify hook, fsnotify_perm(), which is called from the
security code.  This hook is used to allow fsnotify groups to make access
control decisions about events on the system.  We also must change the
generic fsnotify function to return an error code if we intend these hooks
to be in any way useful.
Signed-off-by: NEric Paris <eparis@redhat.com>

fsnotify was using char * when it passed around the d_name.name string
internally but it is actually an unsigned char *.  This patch switches
fsnotify to use unsigned and should silence some pointer signess warnings
which have popped out of xfs.  I do not add -Wpointer-sign to the fsnotify
code as there are still issues with kstrdup and strlen which would pop
out needless warnings.
Signed-off-by: NEric Paris <eparis@redhat.com>

Each group can define their own notification (and secondary_q) merge
function.  Inotify does tail drop, fanotify does matching and drop which
can actually allocate a completely new event.  But for fanotify to properly
deal with permissions events it needs to know the new event which was
ultimately added to the notification queue.  This patch just implements a
void ** argument which is passed to the merge function.  fanotify can use
this field to pass the new event back to higher layers.
Signed-off-by: NEric Paris <eparis@redhat.com>
for fanotify to properly deal with permissions events

This introduces an ordering to fsnotify groups.  With purely asynchronous
notification based "things" implementing fsnotify (inotify, dnotify) ordering
isn't particularly important.  But if people want to use fsnotify for the
basis of sycronous notification or blocking notification ordering becomes
important.

eg. A Hierarchical Storage Management listener would need to get its event
before an AV scanner could get its event (since the HSM would need to
bring the data in for the AV scanner to scan.)  Typically asynchronous notification
would want to run after the AV scanner made any relevant access decisions
so as to not send notification about an event that was denied.
Signed-off-by: NEric Paris <eparis@redhat.com>

fanotify listeners may want to clear all marks.  They may want to do this
to destroy all of their inode marks which have nothing but ignores.
Realistically this is useful for av vendors who update policy and want to
clear all of their cached allows.
Signed-off-by: NEric Paris <eparis@redhat.com>

Some inodes a group may want to never hear about a set of events even if
the inode is modified.  We add a new mark flag which indicates that these
marks should not have their ignored_mask cleared on modification.
Signed-off-by: NEric Paris <eparis@redhat.com>

The ignored_mask is a new mask which is part of fsnotify marks.  A group's
should_send_event() function can use the ignored mask to determine that
certain events are not of interest.  In particular if a group registers a
mask including FS_OPEN on a vfsmount they could add FS_OPEN to the
ignored_mask for individual inodes and not send open events for those
inodes.
Signed-off-by: NEric Paris <eparis@redhat.com>

inotify marks must pin inodes in core.  dnotify doesn't technically need to
since they are closed when the directory is closed.  fanotify also need to
pin inodes in core as it works today.  But the next step is to introduce
the concept of 'ignored masks' which is actually a mask of events for an
inode of no interest.  I claim that these should be liberally sent to the
kernel and should not pin the inode in core.  If the inode is brought back
in the listener will get an event it may have thought excluded, but this is
not a serious situation and one any listener should deal with.

This patch lays the ground work for non-pinning inode marks by using lazy
inode pinning.  We do not pin a mark until it has a non-zero mask entry.  If a
listener new sets a mask we never pin the inode.
Signed-off-by: NEric Paris <eparis@redhat.com>

currently should_send_event in fanotify only cares about marks on inodes.
This patch extends that interface to indicate that it cares about events
that happened on vfsmounts.
Signed-off-by: NEric Paris <eparis@redhat.com>

Per-mount watches allow groups to listen to fsnotify events on an entire
mount.  This patch simply adds and initializes the fields needed in the
vfsmount struct to make this happen.
Signed-off-by: NAndreas Gruenbacher <agruen@suse.de>
Signed-off-by: NEric Paris <eparis@redhat.com>

Much like inode-mark.c has all of the code dealing with marks on inodes
this patch adds a vfsmount-mark.c which has similar code but is intended
for marks on vfsmounts.
Signed-off-by: NEric Paris <eparis@redhat.com>

currently all marking is done by functions in inode-mark.c.  Some of this
is pretty generic and should be instead done in a generic function and we
should only put the inode specific code in inode-mark.c
Signed-off-by: NEric Paris <eparis@redhat.com>

Pass the process identifiers of the triggering processes to fanotify
listeners: this information is useful for event filtering and logging.
Signed-off-by: NAndreas Gruenbacher <agruen@suse.de>
Signed-off-by: NEric Paris <eparis@redhat.com>

previously I used mark_entry when talking about marks on inodes.  The
_entry is pretty useless.  Just use "mark" instead.
Signed-off-by: NEric Paris <eparis@redhat.com>

the _entry portion of fsnotify functions is useless.  Drop it.
Signed-off-by: NEric Paris <eparis@redhat.com>

The name is long and it serves no real purpose.  So rename
fsnotify_mark_entry to just fsnotify_mark.
Signed-off-by: NEric Paris <eparis@redhat.com>

Some fsnotify operations send a struct file.  This is more information than
we technically need.  We instead send a struct path in all cases instead of
sometimes a path and sometimes a file.
Signed-off-by: NAndreas Gruenbacher <agruen@suse.de>
Signed-off-by: NEric Paris <eparis@redhat.com>

To differentiate between inode and vfsmount (or other future) types of
marks we add a flags field and set the inode bit on inode marks (the only
currently supported type of mark)
Signed-off-by: NEric Paris <eparis@redhat.com>

vfsmount marks need mostly the same data as inode specific fields, but for
consistency and understandability we put that data in a vfsmount specific
struct inside a union with inode specific data.
Signed-off-by: NEric Paris <eparis@redhat.com>

The addition of marks on vfs mounts will be simplified if the inode
specific parts of a mark and the vfsmnt specific parts of a mark are
actually in a union so naming can be easy.  This patch just implements the
inode struct and the union.
Signed-off-by: NEric Paris <eparis@redhat.com>

To ensure that a group will not duplicate events when it receives it based
on the vfsmount and the inode should_send_event test we should distinguish
those two cases.  We pass a vfsmount to this function so groups can make
their own determinations.
Signed-off-by: NEric Paris <eparis@redhat.com>

currently all of the notification systems implemented select which inodes
they care about and receive messages only about those inodes (or the
children of those inodes.)  This patch begins to flesh out fsnotify support
for the concept of listeners that want to hear notification for an inode
accessed below a given monut point.  This patch implements a second list
of fsnotify groups to hold these types of groups and a second global mask
to hold the events of interest for this type of group.

The reason we want a second group list and mask is because the inode based
notification should_send_event support which makes each group look for a mark
on the given inode.  With one nfsmount listener that means that every group would
have to take the inode->i_lock, look for their mark, not find one, and return
for every operation.   By seperating vfsmount from inode listeners only when
there is a inode listener will the inode groups have to look for their
mark and take the inode lock.  vfsmount listeners will have to grab the lock and
look for a mark but there should be fewer of them, and one vfsmount listener
won't cause the i_lock to be grabbed and released for every fsnotify group
on every io operation.
Signed-off-by: NEric Paris <eparis@redhat.com>

Simple renaming patch.  fsnotify is about to support mount point listeners
so I am renaming fsnotify_groups and fsnotify_mask to indicate these are lists
used only for groups which have watches on inodes.
Signed-off-by: NEric Paris <eparis@redhat.com>