linux-toradex.git/fs/locks.c, branch v3.18.4

locks: fix NULL-deref in generic_delete_lease

2015-01-27T16:29:40+00:00

commit 52d304eb4eaced9ad04b64ba7cd6ceb5153bbf18 upstream.

commit 0efaa7e82f02fe69c05ad28e905f31fc86e6f08e
  locks: generic_delete_lease doesn't need a file_lock at all

moves the call to fl->fl_lmops->lm_change() to a place in the
code where fl might be a non-lease lock.
When that happens, fl_lmops is NULL and an Oops ensures.

So add an extra test to restore correct functioning.

Reported-by: Linda Walsh 
Link: https://bugzilla.suse.com/show_bug.cgi?id=912569
Fixes: 0efaa7e82f02fe69c05ad28e905f31fc86e6f08e
Signed-off-by: NeilBrown 
Signed-off-by: Jeff Layton 
Signed-off-by: Greg Kroah-Hartman

locks: flock_make_lock should return a struct file_lock (or PTR_ERR)

2014-10-07T18:06:13+00:00

Eliminate the need for a return pointer.

Signed-off-by: Jeff Layton 
Reviewed-by: Christoph Hellwig

locks: set fl_owner for leases to filp instead of current->files

2014-10-07T18:06:13+00:00

Like flock locks, leases are owned by the file description. Now that the
i_have_this_lease check in __break_lease is gone, we don't actually use
the fl_owner for leases for anything. So, it's now safe to set this more
appropriately to the same value as the fl_file.

While we're at it, fix up the comments over the fl_owner_t definition
since they're rather out of date.

Signed-off-by: Jeff Layton

locks: give lm_break a return value

2014-10-07T18:06:13+00:00

Christoph suggests:

   "Add a return value to lm_break so that the lock manager can tell the
    core code "you can delete this lease right now".  That gets rid of
    the games with the timeout which require all kinds of race avoidance
    code in the users."

Do that here and have the nfsd lease break routine use it when it detects
that there was a race between setting up the lease and it being broken.

Signed-off-by: Jeff Layton 
Reviewed-by: Christoph Hellwig

locks: __break_lease cleanup in preparation of allowing direct removal of leases

2014-10-07T18:06:13+00:00

Eliminate an unneeded "flock" variable. We can use "fl" as a loop cursor
everywhere. Add a any_leases_conflict helper function as well to
consolidate a bit of code.

Signed-off-by: Jeff Layton 
Reviewed-by: Christoph Hellwig

locks: remove i_have_this_lease check from __break_lease

2014-10-07T18:06:13+00:00

I think that the intent of this code was to ensure that a process won't
deadlock if it has one fd open with a lease on it and then breaks that
lease by opening another fd. In that case it'll treat the __break_lease
call as if it were non-blocking.

This seems wrong -- the process could (for instance) be multithreaded
and managing different fds via different threads. I also don't see any
mention of this limitation in the (somewhat sketchy) documentation.

Remove the check and the non-blocking behavior when i_have_this_lease
is true.

Signed-off-by: Jeff Layton

locks: move freeing of leases outside of i_lock

2014-10-07T18:06:13+00:00

There was only one place where we still could free a file_lock while
holding the i_lock -- lease_modify. Add a new list_head argument to the
lm_change operation, pass in a private list when calling it, and fix
those callers to dispose of the list once the lock has been dropped.

Signed-off-by: Jeff Layton 
Reviewed-by: Christoph Hellwig

locks: move i_lock acquisition into generic_*_lease handlers

2014-10-07T18:06:13+00:00

Now that we have a saner internal API for managing leases, we no longer
need to mandate that the inode->i_lock be held over most of the lease
code. Push it down into generic_add_lease and generic_delete_lease.

Signed-off-by: Jeff Layton 
Reviewed-by: Christoph Hellwig

locks: define a lm_setup handler for leases

2014-10-07T18:06:12+00:00

...and move the fasync setup into it for fcntl lease calls. At the same
time, change the semantics of how the file_lock double-pointer is
handled. Up until now, on a successful lease return you got a pointer to
the lock on the list. This is bad, since that pointer can no longer be
relied on as valid once the inode->i_lock has been released.

Change the code to instead just zero out the pointer if the lease we
passed in ended up being used. Then the callers can just check to see
if it's NULL after the call and free it if it isn't.

The priv argument has the same semantics. The lm_setup function can
zero the pointer out to signal to the caller that it should not be
freed after the function returns.

Signed-off-by: Jeff Layton 
Reviewed-by: Christoph Hellwig

locks: plumb a "priv" pointer into the setlease routines

2014-10-07T18:06:12+00:00

In later patches, we're going to add a new lock_manager_operation to
finish setting up the lease while still holding the i_lock.  To do
this, we'll need to pass a little bit of info in the fcntl setlease
case (primarily an fasync structure). Plumb the extra pointer into
there in advance of that.

We declare this pointer as a void ** to make it clear that this is
private info, and that the caller isn't required to set this unless
the lm_setup specifically requires it.

Signed-off-by: Jeff Layton 
Reviewed-by: Christoph Hellwig