On 20/12/2020 12:06, Sakari Ailus wrote:
> 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@xxxxxxxxxx>
> Reported-by: syzbot+1115e79c8df6472c612b@xxxxxxxxxxxxxxxxxxxxxxxxx
> Fixes: d14e6d76ebf7 ("[media] v4l: Add multi-planar ioctl handling code")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
Acked-by: Hans Verkuil <hverkuil-cisco@xxxxxxxxx>
Regards,
Hans
> ---
> drivers/media/v4l2-core/v4l2-ioctl.c | 31 +++++++++++++---------------
> 1 file changed, 14 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
> index 3198abdd538ce..f42a779948779 100644
> --- a/drivers/media/v4l2-core/v4l2-ioctl.c
> +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
> @@ -3283,7 +3283,7 @@ video_usercopy(struct file *file, unsigned int orig_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;
> @@ -3318,27 +3318,21 @@ video_usercopy(struct file *file, unsigned int orig_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 (in_compat_syscall())
> - err = v4l2_compat_get_array_args(file, mbuf, user_ptr,
> - array_size, orig_cmd,
> - parg);
> + err = v4l2_compat_get_array_args(file, array_buf,
> + user_ptr, array_size,
> + orig_cmd, parg);
> else
> - err = copy_from_user(mbuf, user_ptr, array_size) ?
> + err = copy_from_user(array_buf, user_ptr, array_size) ?
> -EFAULT : 0;
> if (err)
> goto out_array_args;
> - *kernel_ptr = mbuf;
> + *kernel_ptr = array_buf;
> }
>
> /* Handles IOCTL */
> @@ -3360,12 +3354,14 @@ video_usercopy(struct file *file, unsigned int orig_cmd, unsigned long arg,
> if (in_compat_syscall()) {
> int put_err;
>
> - put_err = v4l2_compat_put_array_args(file, user_ptr, mbuf,
> - array_size, orig_cmd,
> + put_err = v4l2_compat_put_array_args(file, user_ptr,
> + array_buf,
> + array_size,
> + orig_cmd,
> parg);
> if (put_err)
> err = put_err;
> - } else if (copy_to_user(user_ptr, mbuf, array_size)) {
> + } else if (copy_to_user(user_ptr, array_buf, array_size)) {
> err = -EFAULT;
> }
> goto out_array_args;
> @@ -3381,6 +3377,7 @@ video_usercopy(struct file *file, unsigned int orig_cmd, unsigned long arg,
> if (video_put_user((void __user *)arg, parg, cmd, orig_cmd))
> err = -EFAULT;
> out:
> + kvfree(array_buf);
> kvfree(mbuf);
> return err;
> }
>
