linux-kernel - [PATCH 4.1 43/46] locks: have flock_lock_file take an inode pointer instead of a filp

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Date:	Fri, 23 Oct 2015 10:46:29 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Jeff Layton <jeff.layton@...marydata.com>,
	"J. Bruce Fields" <bfields@...ldses.org>,
	William Dauchy <william@...di.net>
Subject: [PATCH 4.1 43/46] locks: have flock_lock_file take an inode pointer instead of a filp

4.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jeff Layton <jeff.layton@...marydata.com>

commit bcd7f78d078ff6197715c1ed070c92aca57ec12c upstream.

...and rename it to better describe how it works.

In order to fix a use-after-free in NFS, we need to be able to remove
locks from an inode after the filp associated with them may have already
been freed. flock_lock_file already only dereferences the filp to get to
the inode, so just change it so the callers do that.

All of the callers already pass in a lock request that has the fl_file
set properly, so we don't need to pass it in individually. With that
change it now only dereferences the filp to get to the inode, so just
push that out to the callers.

Signed-off-by: Jeff Layton <jeff.layton@...marydata.com>
Reviewed-by: "J. Bruce Fields" <bfields@...ldses.org>
Tested-by: "J. Bruce Fields" <bfields@...ldses.org>
Cc: William Dauchy <william@...di.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/locks.c |   12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

--- a/fs/locks.c
+++ b/fs/locks.c
@@ -862,12 +862,11 @@ static int posix_locks_deadlock(struct f
  * whether or not a lock was successfully freed by testing the return
  * value for -ENOENT.
  */
-static int flock_lock_file(struct file *filp, struct file_lock *request)
+static int flock_lock_inode(struct inode *inode, struct file_lock *request)
 {
 	struct file_lock *new_fl = NULL;
 	struct file_lock *fl;
 	struct file_lock_context *ctx;
-	struct inode *inode = file_inode(filp);
 	int error = 0;
 	bool found = false;
 	LIST_HEAD(dispose);
@@ -890,7 +889,7 @@ static int flock_lock_file(struct file *
 		goto find_conflict;
 
 	list_for_each_entry(fl, &ctx->flc_flock, fl_list) {
-		if (filp != fl->fl_file)
+		if (request->fl_file != fl->fl_file)
 			continue;
 		if (request->fl_type == fl->fl_type)
 			goto out;
@@ -1862,7 +1861,7 @@ int flock_lock_file_wait(struct file *fi
 	int error;
 	might_sleep();
 	for (;;) {
-		error = flock_lock_file(filp, fl);
+		error = flock_lock_inode(file_inode(filp), fl);
 		if (error != FILE_LOCK_DEFERRED)
 			break;
 		error = wait_event_interruptible(fl->fl_wait, !fl->fl_next);
@@ -2401,7 +2400,8 @@ locks_remove_flock(struct file *filp)
 		.fl_type = F_UNLCK,
 		.fl_end = OFFSET_MAX,
 	};
-	struct file_lock_context *flctx = file_inode(filp)->i_flctx;
+	struct inode *inode = file_inode(filp);
+	struct file_lock_context *flctx = inode->i_flctx;
 
 	if (list_empty(&flctx->flc_flock))
 		return;
@@ -2409,7 +2409,7 @@ locks_remove_flock(struct file *filp)
 	if (filp->f_op->flock)
 		filp->f_op->flock(filp, F_SETLKW, &fl);
 	else
-		flock_lock_file(filp, &fl);
+		flock_lock_inode(inode, &fl);
 
 	if (fl.fl_ops && fl.fl_ops->fl_release_private)
 		fl.fl_ops->fl_release_private(&fl);


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