linux-kernel - [RFC][PATCH 01/42] drm_mode_create_lease_ioctl(): fix open-coded filp_clone

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Message-Id: <20180711022206.12571-1-viro@ZenIV.linux.org.uk>
Date:   Wed, 11 Jul 2018 03:21:25 +0100
From:   Al Viro <viro@...IV.linux.org.uk>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        Miklos Szeredi <mszeredi@...hat.com>
Subject: [RFC][PATCH 01/42] drm_mode_create_lease_ioctl(): fix open-coded filp_clone_open()

From: Al Viro <viro@...iv.linux.org.uk>

Failure of ->open() should *not* be followed by fput().  Fixed by
using filp_clone_open(), which gets the cleanups right.

Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
---
 drivers/gpu/drm/drm_lease.c | 16 +---------------
 fs/internal.h               |  1 -
 include/linux/fs.h          |  1 +
 3 files changed, 2 insertions(+), 16 deletions(-)

diff --git a/drivers/gpu/drm/drm_lease.c b/drivers/gpu/drm/drm_lease.c
index 50c73c0a20b9..d638c0fb3418 100644
--- a/drivers/gpu/drm/drm_lease.c
+++ b/drivers/gpu/drm/drm_lease.c
@@ -553,24 +553,13 @@ int drm_mode_create_lease_ioctl(struct drm_device *dev,
 
 	/* Clone the lessor file to create a new file for us */
 	DRM_DEBUG_LEASE("Allocating lease file\n");
-	path_get(&lessor_file->f_path);
-	lessee_file = alloc_file(&lessor_file->f_path,
-				 lessor_file->f_mode,
-				 fops_get(lessor_file->f_inode->i_fop));
-
+	lessee_file = filp_clone_open(lessor_file);
 	if (IS_ERR(lessee_file)) {
 		ret = PTR_ERR(lessee_file);
 		goto out_lessee;
 	}
 
-	/* Initialize the new file for DRM */
-	DRM_DEBUG_LEASE("Initializing the file with %p\n", lessee_file->f_op->open);
-	ret = lessee_file->f_op->open(lessee_file->f_inode, lessee_file);
-	if (ret)
-		goto out_lessee_file;
-
 	lessee_priv = lessee_file->private_data;
-
 	/* Change the file to a master one */
 	drm_master_put(&lessee_priv->master);
 	lessee_priv->master = lessee;
@@ -588,9 +577,6 @@ int drm_mode_create_lease_ioctl(struct drm_device *dev,
 	DRM_DEBUG_LEASE("drm_mode_create_lease_ioctl succeeded\n");
 	return 0;
 
-out_lessee_file:
-	fput(lessee_file);
-
 out_lessee:
 	drm_master_put(&lessee);
 
diff --git a/fs/internal.h b/fs/internal.h
index 980d005b21b4..5645b4ebf494 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -127,7 +127,6 @@ int do_fchownat(int dfd, const char __user *filename, uid_t user, gid_t group,
 
 extern int open_check_o_direct(struct file *f);
 extern int vfs_open(const struct path *, struct file *, const struct cred *);
-extern struct file *filp_clone_open(struct file *);
 
 /*
  * inode.c
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 5c91108846db..aa9b4c169ed2 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2422,6 +2422,7 @@ extern struct file *filp_open(const char *, int, umode_t);
 extern struct file *file_open_root(struct dentry *, struct vfsmount *,
 				   const char *, int, umode_t);
 extern struct file * dentry_open(const struct path *, int, const struct cred *);
+extern struct file *filp_clone_open(struct file *);
 extern int filp_close(struct file *, fl_owner_t id);
 
 extern struct filename *getname_flags(const char __user *, int, int *);
-- 
2.11.0