Re: [PATCH] media: v4l2-ioctl: fix function types for IOCTL_INFO_STD
From: Kees Cook
Date: Mon Apr 30 2018 - 18:58:24 EST
On Fri, Apr 27, 2018 at 11:59 AM, Sami Tolvanen <samitolvanen@xxxxxxxxxx> wrote:
> This change fixes indirect call mismatches with Control-Flow Integrity
> checking, which are caused by calling standard ioctls using a function
> pointer that doesn't match the type of the actual function.
>
> Signed-off-by: Sami Tolvanen <samitolvanen@xxxxxxxxxx>
I think this actually makes things much more readable in the end. Thanks!
Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
-Kees
> ---
> drivers/media/v4l2-core/v4l2-ioctl.c | 72 ++++++++++++++++++----------
> 1 file changed, 46 insertions(+), 26 deletions(-)
>
> diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
> index f48c505550e0..d50a06ab3509 100644
> --- a/drivers/media/v4l2-core/v4l2-ioctl.c
> +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
> @@ -2489,11 +2489,8 @@ struct v4l2_ioctl_info {
> unsigned int ioctl;
> u32 flags;
> const char * const name;
> - union {
> - u32 offset;
> - int (*func)(const struct v4l2_ioctl_ops *ops,
> - struct file *file, void *fh, void *p);
> - } u;
> + int (*func)(const struct v4l2_ioctl_ops *ops, struct file *file,
> + void *fh, void *p);
> void (*debug)(const void *arg, bool write_only);
> };
>
> @@ -2501,27 +2498,24 @@ struct v4l2_ioctl_info {
> #define INFO_FL_PRIO (1 << 0)
> /* This control can be valid if the filehandle passes a control handler. */
> #define INFO_FL_CTRL (1 << 1)
> -/* This is a standard ioctl, no need for special code */
> -#define INFO_FL_STD (1 << 2)
> /* This is ioctl has its own function */
> -#define INFO_FL_FUNC (1 << 3)
> +#define INFO_FL_FUNC (1 << 2)
> /* Queuing ioctl */
> -#define INFO_FL_QUEUE (1 << 4)
> +#define INFO_FL_QUEUE (1 << 3)
> /* Always copy back result, even on error */
> -#define INFO_FL_ALWAYS_COPY (1 << 5)
> +#define INFO_FL_ALWAYS_COPY (1 << 4)
> /* Zero struct from after the field to the end */
> #define INFO_FL_CLEAR(v4l2_struct, field) \
> ((offsetof(struct v4l2_struct, field) + \
> sizeof(((struct v4l2_struct *)0)->field)) << 16)
> #define INFO_FL_CLEAR_MASK (_IOC_SIZEMASK << 16)
>
> -#define IOCTL_INFO_STD(_ioctl, _vidioc, _debug, _flags) \
> - [_IOC_NR(_ioctl)] = { \
> - .ioctl = _ioctl, \
> - .flags = _flags | INFO_FL_STD, \
> - .name = #_ioctl, \
> - .u.offset = offsetof(struct v4l2_ioctl_ops, _vidioc), \
> - .debug = _debug, \
> +#define DEFINE_IOCTL_STD_FNC(_vidioc) \
> + static int __v4l_ ## _vidioc ## _fnc( \
> + const struct v4l2_ioctl_ops *ops, \
> + struct file *file, void *fh, void *p) \
> + { \
> + return ops->_vidioc(file, fh, p); \
> }
>
> #define IOCTL_INFO_FNC(_ioctl, _func, _debug, _flags) \
> @@ -2529,10 +2523,42 @@ struct v4l2_ioctl_info {
> .ioctl = _ioctl, \
> .flags = _flags | INFO_FL_FUNC, \
> .name = #_ioctl, \
> - .u.func = _func, \
> + .func = _func, \
> .debug = _debug, \
> }
>
> +#define IOCTL_INFO_STD(_ioctl, _vidioc, _debug, _flags) \
> + IOCTL_INFO_FNC(_ioctl, __v4l_ ## _vidioc ## _fnc, _debug, _flags)
> +
> +DEFINE_IOCTL_STD_FNC(vidioc_g_fbuf)
> +DEFINE_IOCTL_STD_FNC(vidioc_s_fbuf)
> +DEFINE_IOCTL_STD_FNC(vidioc_expbuf)
> +DEFINE_IOCTL_STD_FNC(vidioc_g_std)
> +DEFINE_IOCTL_STD_FNC(vidioc_g_audio)
> +DEFINE_IOCTL_STD_FNC(vidioc_s_audio)
> +DEFINE_IOCTL_STD_FNC(vidioc_g_input)
> +DEFINE_IOCTL_STD_FNC(vidioc_g_edid)
> +DEFINE_IOCTL_STD_FNC(vidioc_s_edid)
> +DEFINE_IOCTL_STD_FNC(vidioc_g_output)
> +DEFINE_IOCTL_STD_FNC(vidioc_g_audout)
> +DEFINE_IOCTL_STD_FNC(vidioc_s_audout)
> +DEFINE_IOCTL_STD_FNC(vidioc_g_jpegcomp)
> +DEFINE_IOCTL_STD_FNC(vidioc_s_jpegcomp)
> +DEFINE_IOCTL_STD_FNC(vidioc_enumaudio)
> +DEFINE_IOCTL_STD_FNC(vidioc_enumaudout)
> +DEFINE_IOCTL_STD_FNC(vidioc_enum_framesizes)
> +DEFINE_IOCTL_STD_FNC(vidioc_enum_frameintervals)
> +DEFINE_IOCTL_STD_FNC(vidioc_g_enc_index)
> +DEFINE_IOCTL_STD_FNC(vidioc_encoder_cmd)
> +DEFINE_IOCTL_STD_FNC(vidioc_try_encoder_cmd)
> +DEFINE_IOCTL_STD_FNC(vidioc_decoder_cmd)
> +DEFINE_IOCTL_STD_FNC(vidioc_try_decoder_cmd)
> +DEFINE_IOCTL_STD_FNC(vidioc_s_dv_timings)
> +DEFINE_IOCTL_STD_FNC(vidioc_g_dv_timings)
> +DEFINE_IOCTL_STD_FNC(vidioc_enum_dv_timings)
> +DEFINE_IOCTL_STD_FNC(vidioc_query_dv_timings)
> +DEFINE_IOCTL_STD_FNC(vidioc_dv_timings_cap)
> +
> static struct v4l2_ioctl_info v4l2_ioctls[] = {
> IOCTL_INFO_FNC(VIDIOC_QUERYCAP, v4l_querycap, v4l_print_querycap, 0),
> IOCTL_INFO_FNC(VIDIOC_ENUM_FMT, v4l_enum_fmt, v4l_print_fmtdesc, INFO_FL_CLEAR(v4l2_fmtdesc, type)),
> @@ -2717,14 +2743,8 @@ static long __video_do_ioctl(struct file *file,
> }
>
> write_only = _IOC_DIR(cmd) == _IOC_WRITE;
> - if (info->flags & INFO_FL_STD) {
> - typedef int (*vidioc_op)(struct file *file, void *fh, void *p);
> - const void *p = vfd->ioctl_ops;
> - const vidioc_op *vidioc = p + info->u.offset;
> -
> - ret = (*vidioc)(file, fh, arg);
> - } else if (info->flags & INFO_FL_FUNC) {
> - ret = info->u.func(ops, file, fh, arg);
> + if (info->flags & INFO_FL_FUNC) {
> + ret = info->func(ops, file, fh, arg);
> } else if (!ops->vidioc_default) {
> ret = -ENOTTY;
> } else {
> --
> 2.17.0.441.gb46fe60e1d-goog
>
--
Kees Cook
Pixel Security