[PATCH FOR stable v5.4 1/1] media: v4l: ioctl: Fix memory leak in video_usercopy

[Sakari Ailus <sakari.ailus@linux.intel.com>]

[ Upstream commit fb18802a338b36f675a388fc03d2aa504a0d0899 ]

When an IOCTL with argument size larger than 128 that also used array
arguments were handled, two memory allocations were made but alas, only
the latter one of them was released. This happened because there was only
a single local variable to hold such a temporary allocation.

Fix this by adding separate variables to hold the pointers to the
temporary allocations.

Reported-by: Arnd Bergmann <arnd@kernel.org>
Reported-by: syzbot+1115e79c8df6472c612b@syzkaller.appspotmail.com
Fixes: d14e6d76ebf7 ("[media] v4l: Add multi-planar ioctl handling code")
Cc: stable@vger.kernel.org
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
---
 drivers/media/v4l2-core/v4l2-ioctl.c | 19 +++++++------------
 1 file changed, 7 insertions(+), 12 deletions(-)

diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
index 58868d7129ebd..24db33f803c06 100644
--- a/drivers/media/v4l2-core/v4l2-ioctl.c
+++ b/drivers/media/v4l2-core/v4l2-ioctl.c
@@ -3016,7 +3016,7 @@ video_usercopy(struct file *file, unsigned int cmd, unsigned long arg,
 	       v4l2_kioctl func)
 {
 	char	sbuf[128];
-	void    *mbuf = NULL;
+	void    *mbuf = NULL, *array_buf = NULL;
 	void	*parg = (void *)arg;
 	long	err  = -EINVAL;
 	bool	has_array_args;
@@ -3075,20 +3075,14 @@ video_usercopy(struct file *file, unsigned int cmd, unsigned long arg,
 	has_array_args = err;
 
 	if (has_array_args) {
-		/*
-		 * When adding new types of array args, make sure that the
-		 * parent argument to ioctl (which contains the pointer to the
-		 * array) fits into sbuf (so that mbuf will still remain
-		 * unused up to here).
-		 */
-		mbuf = kvmalloc(array_size, GFP_KERNEL);
+		array_buf = kvmalloc(array_size, GFP_KERNEL);
 		err = -ENOMEM;
-		if (NULL == mbuf)
+		if (array_buf == NULL)
 			goto out_array_args;
 		err = -EFAULT;
-		if (copy_from_user(mbuf, user_ptr, array_size))
+		if (copy_from_user(array_buf, user_ptr, array_size))
 			goto out_array_args;
-		*kernel_ptr = mbuf;
+		*kernel_ptr = array_buf;
 	}
 
 	/* Handles IOCTL */
@@ -3107,7 +3101,7 @@ video_usercopy(struct file *file, unsigned int cmd, unsigned long arg,
 
 	if (has_array_args) {
 		*kernel_ptr = (void __force *)user_ptr;
-		if (copy_to_user(user_ptr, mbuf, array_size))
+		if (copy_to_user(user_ptr, array_buf, array_size))
 			err = -EFAULT;
 		goto out_array_args;
 	}
@@ -3129,6 +3123,7 @@ video_usercopy(struct file *file, unsigned int cmd, unsigned long arg,
 	}
 
 out:
+	kvfree(array_buf);
 	kvfree(mbuf);
 	return err;
 }
-- 
2.20.1