Commit 0e7d523b authored Jan 15, 2025 by Al Viro Committed by Greg Kroah-Hartman Jan 16, 2025

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: b46271ec "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>

parent 2217573f

drivers/misc/ntsync.c

+6 −4

Original line number	Diff line number	Diff line
		@@ -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;
		}