Re: [PATCH 4/4] filelock: WARN_ON_ONCE when ->fl_file and filp don't match

[Jeff Layton <jlayton@kernel.org>]

On Fri, 2022-11-11 at 14:36 -0500, Jeff Layton wrote:
> vfs_lock_file, vfs_test_lock and vfs_cancel_lock all take both a struct
> file argument and a file_lock. The file_lock has a fl_file field in it
> howevever and it _must_ match the file passed in.
> 
> While most of the locks.c routines use the separately-passed file
> argument, some filesystems rely on fl_file being filled out correctly.
> 
> I'm working on a patch series to remove the redundant argument from
> these routines, but for now, let's ensure that the callers always set
> this properly by issuing a WARN_ON_ONCE if they ever don't match.
> 
> Cc: Chuck Lever <chuck.lever@oracle.com>
> Cc: Trond Myklebust <trondmy@hammerspace.com>
> Signed-off-by: Jeff Layton <jlayton@kernel.org>
> ---
>  fs/locks.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/fs/locks.c b/fs/locks.c
> index 607f94a0e789..5876c8ff0edc 100644
> --- a/fs/locks.c
> +++ b/fs/locks.c
> @@ -2146,6 +2146,7 @@ SYSCALL_DEFINE2(flock, unsigned int, fd, unsigned int, cmd)
>   */
>  int vfs_test_lock(struct file *filp, struct file_lock *fl)
>  {
> +	WARN_ON_ONCE(filp != fl->fl_file);
>  	if (filp->f_op->lock)
>  		return filp->f_op->lock(filp, F_GETLK, fl);
>  	posix_test_lock(filp, fl);
> @@ -2295,6 +2296,7 @@ int fcntl_getlk(struct file *filp, unsigned int cmd, struct flock *flock)
>   */
>  int vfs_lock_file(struct file *filp, unsigned int cmd, struct file_lock *fl, struct file_lock *conf)
>  {
> +	WARN_ON_ONCE(filp != fl->fl_file);
>  	if (filp->f_op->lock)
>  		return filp->f_op->lock(filp, cmd, fl);
>  	else
> @@ -2663,6 +2665,7 @@ void locks_remove_file(struct file *filp)
>   */
>  int vfs_cancel_lock(struct file *filp, struct file_lock *fl)
>  {
> +	WARN_ON_ONCE(filp != fl->fl_file);
>  	if (filp->f_op->lock)
>  		return filp->f_op->lock(filp, F_CANCELLK, fl);
>  	return 0;

Oops, I meant to cc linux-fsdevel here too. I'll plan to do that on the
next posting (assuming that I need to do one).

Cheers,
-- 
Jeff Layton <jlayton@kernel.org>