media: omap3isp: Use struct_group() for memcpy() region

In preparation for FORTIFY_SOURCE performing compile-time and run-time
field bounds checking for memcpy(), memmove(), and memset(), avoid
intentionally writing across neighboring fields. Wrap the target region
in struct_group(). This additionally fixes a theoretical misalignment
of the copy (since the size of "buf" changes between 64-bit and 32-bit,
but this is likely never built for 64-bit).

FWIW, I think this code is totally broken on 64-bit (which appears to
not be a "real" build configuration): 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.

Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Sakari Ailus <sakari.ailus@linux.intel.com>
Cc: linux-media@vger.kernel.org
Fixes: 378e3f81cb56 ("media: omap3isp: support 64-bit version of omap3isp_stat_data")
Cc: stable@vger.kernel.org
Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Link: https://lore.kernel.org/lkml/20211215220505.GB21862@embeddedor
Signed-off-by: Kees Cook <keescook@chromium.org>

1 files changed, 3 insertions, 2 deletions

diff --git a/drivers/media/platform/omap3isp/ispstat.c b/drivers/media/platform/omap3isp/ispstat.c
index 5b9b57f4d9bf..68cf68dbcace 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.frame, sizeof(data->frame));
 
 	return 0;
 }