ntsync: fix a file reference leak in drivers/misc/ntsync.c

	struct ntsync_obj contains a reference to struct file
and that reference contributes to refcount - ntsync_alloc_obj()
grabs it.  Normally the object is destroyed (and reference
to obj->file dropped) in ntsync_obj_release().  However, in
case of ntsync_obj_get_fd() failure the object is destroyed
directly by its creator.

	That case should also drop obj->file; plain kfree(obj)
is not enough there - it ends up leaking struct file * reference.

	Take that logics into a helper (ntsync_free_obj()) and
use it in both codepaths that destroy ntsync_obj instances.

Fixes: b46271ec40a05 "ntsync: Introduce NTSYNC_IOC_CREATE_SEM"
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Reviewed-by: Elizabeth Figura <zfigura@codeweavers.com>
Link: https://lore.kernel.org/r/20250115025002.GA1977892@ZenIV
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/misc/ntsync.c b/drivers/misc/ntsync.c
index 457ff28b789f752de0a82aae6bf14ecee51cbc15..b6441e9789744dc67b863594f68c1d09d974fbd6 100644 (file)
--- a/drivers/misc/ntsync.c
+++ b/drivers/misc/ntsync.c
@@ -651,13 +651,15 @@ static int ntsync_event_read(struct ntsync_obj *event, void __user *argp)
        return 0;
 }
 
-static int ntsync_obj_release(struct inode *inode, struct file *file)
+static void ntsync_free_obj(struct ntsync_obj *obj)
 {
-       struct ntsync_obj *obj = file->private_data;
-
        fput(obj->dev->file);
        kfree(obj);
+}
 
+static int ntsync_obj_release(struct inode *inode, struct file *file)
+{
+       ntsync_free_obj(file->private_data);
        return 0;
 }
 
@@ -755,7 +757,7 @@ static int ntsync_create_sem(struct ntsync_device *dev, void __user *argp)
        sem->u.sem.max = args.max;
        fd = ntsync_obj_get_fd(sem);
        if (fd < 0)
-               kfree(sem);
+               ntsync_free_obj(sem);
 
        return fd;
 }