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Date: Wed, 16 Jun 2021 22:43:03 +0300
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: Kees Cook <keescook@...omium.org>
Cc: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
Arnd Bergmann <arnd@...db.de>,
"Gustavo A. R. Silva" <gustavoars@...nel.org>,
Sakari Ailus <sakari.ailus@...ux.intel.com>,
linux-kernel@...r.kernel.org, linux-media@...r.kernel.org
Subject: Re: [PATCH] media: omap3isp: Extract struct group for memcpy() region
Hi Kees,
Thank you for the patch.
On Wed, Jun 16, 2021 at 11:59:38AM -0700, Kees Cook wrote:
> Avoid writing past the end of a structure member by wrapping the target
> region in a common named structure. This additionally fixes a
> misalignment of the copy (since the size of "buf" changes between 64-bit
> and 32-bit).
Could you have been mislead by the data64 name ? The difference between
omap3isp_stat_data_time and omap3isp_stat_data_time32 is the size of the
ts field, using 32-bit timestamps with legacy userspace, and 64-bit
timestamps with more recent userspace. In both cases we're dealing with
a 32-bit platform, as the omap3isp is not used in any 64-bit ARM SoC.
The size of void __user *buf is thus 4 bytes in all cases, as is __u32
buf.
> I actually think this code is completely unused in the real world:
> I don't think it could have ever worked, as it would either always
> fail (with an uninitialized data->buf_size) or would cause corruption
> in userspace due to the copy_to_user() in the call path against an
> uninitialized data->buf value:
>
> omap3isp_stat_request_statistics_time32(...)
> struct omap3isp_stat_data data64;
> ...
> omap3isp_stat_request_statistics(stat, &data64);
>
> int omap3isp_stat_request_statistics(struct ispstat *stat,
> struct omap3isp_stat_data *data)
> ...
> buf = isp_stat_buf_get(stat, data);
>
> static struct ispstat_buffer *isp_stat_buf_get(struct ispstat *stat,
> struct omap3isp_stat_data *data)
> ...
> if (buf->buf_size > data->buf_size) {
> ...
> return ERR_PTR(-EINVAL);
> }
> ...
> rval = copy_to_user(data->buf,
> buf->virt_addr,
> buf->buf_size);
>
> Regardless, additionally initialize data64 to be zero-filled to avoid
> undefined behavior.
>
> Fixes: 378e3f81cb56 ("media: omap3isp: support 64-bit version of omap3isp_stat_data")
> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---
> drivers/media/platform/omap3isp/ispstat.c | 5 +--
> include/uapi/linux/omap3isp.h | 44 +++++++++++++++++------
> 2 files changed, 36 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/media/platform/omap3isp/ispstat.c b/drivers/media/platform/omap3isp/ispstat.c
> index 5b9b57f4d9bf..ea8222fed38e 100644
> --- a/drivers/media/platform/omap3isp/ispstat.c
> +++ b/drivers/media/platform/omap3isp/ispstat.c
> @@ -512,7 +512,7 @@ int omap3isp_stat_request_statistics(struct ispstat *stat,
> int omap3isp_stat_request_statistics_time32(struct ispstat *stat,
> struct omap3isp_stat_data_time32 *data)
> {
> - struct omap3isp_stat_data data64;
> + struct omap3isp_stat_data data64 = { };
> int ret;
>
> ret = omap3isp_stat_request_statistics(stat, &data64);
> @@ -521,7 +521,8 @@ int omap3isp_stat_request_statistics_time32(struct ispstat *stat,
>
> data->ts.tv_sec = data64.ts.tv_sec;
> data->ts.tv_usec = data64.ts.tv_usec;
> - memcpy(&data->buf, &data64.buf, sizeof(*data) - sizeof(data->ts));
> + data->buf = (uintptr_t)data64.buf;
> + memcpy(&data->frame, &data64.buf, sizeof(data->frame));
>
> return 0;
> }
> diff --git a/include/uapi/linux/omap3isp.h b/include/uapi/linux/omap3isp.h
> index 87b55755f4ff..0a16af91621f 100644
> --- a/include/uapi/linux/omap3isp.h
> +++ b/include/uapi/linux/omap3isp.h
> @@ -159,13 +159,25 @@ struct omap3isp_h3a_aewb_config {
> };
>
> /**
> - * struct omap3isp_stat_data - Statistic data sent to or received from user
> - * @ts: Timestamp of returned framestats.
> - * @buf: Pointer to pass to user.
> + * struct omap3isp_stat_frame - Statistic data without timestamp nor pointer.
> + * @buf_size: Size of buffer.
> * @frame_number: Frame number of requested stats.
> * @cur_frame: Current frame number being processed.
> * @config_counter: Number of the configuration associated with the data.
> */
> +struct omap3isp_stat_frame {
> + __u32 buf_size;
> + __u16 frame_number;
> + __u16 cur_frame;
> + __u16 config_counter;
> +};
> +
> +/**
> + * struct omap3isp_stat_data - Statistic data sent to or received from user
> + * @ts: Timestamp of returned framestats.
> + * @buf: Pointer to pass to user.
> + * @frame: Statistic data for frame.
> + */
> struct omap3isp_stat_data {
> #ifdef __KERNEL__
> struct {
> @@ -176,10 +188,15 @@ struct omap3isp_stat_data {
> struct timeval ts;
> #endif
> void __user *buf;
> - __u32 buf_size;
> - __u16 frame_number;
> - __u16 cur_frame;
> - __u16 config_counter;
> + union {
> + struct {
> + __u32 buf_size;
> + __u16 frame_number;
> + __u16 cur_frame;
> + __u16 config_counter;
> + };
> + struct omap3isp_stat_frame frame;
> + };
> };
>
> #ifdef __KERNEL__
> @@ -189,10 +206,15 @@ struct omap3isp_stat_data_time32 {
> __s32 tv_usec;
> } ts;
> __u32 buf;
> - __u32 buf_size;
> - __u16 frame_number;
> - __u16 cur_frame;
> - __u16 config_counter;
> + union {
> + struct {
> + __u32 buf_size;
> + __u16 frame_number;
> + __u16 cur_frame;
> + __u16 config_counter;
> + };
> + struct omap3isp_stat_frame frame;
> + };
> };
> #endif
>
--
Regards,
Laurent Pinchart
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