[PATCH 5.19 025/717] usb: gadget: uvc: Fix argument to sizeof() in uvc_register_video()

Greg Kroah-Hartman
2022-10-22T07:36:15Z

From: Nathan Chancellor <nathan@kernel.org>

commit a15e17acce5aaae54243f55a7349c2225450b9bc upstream.

When building s390 allmodconfig after commit 9b91a6523078 ("usb: gadget:
uvc: increase worker prio to WQ_HIGHPRI"), the following error occurs:

In file included from ../include/linux/string.h:253,
from ../include/linux/bitmap.h:11,
from ../include/linux/cpumask.h:12,
from ../include/linux/smp.h:13,
from ../include/linux/lockdep.h:14,
from ../include/linux/rcupdate.h:29,
from ../include/linux/rculist.h:11,
from ../include/linux/pid.h:5,
from ../include/linux/sched.h:14,
from ../include/linux/ratelimit.h:6,
from ../include/linux/dev_printk.h:16,
from ../include/linux/device.h:15,
from ../drivers/usb/gadget/function/f_uvc.c:9:
In function ‘fortify_memset_chk’,
inlined from ‘uvc_register_video’ at ../drivers/usb/gadget/function/f_uvc.c:424:2:
../include/linux/fortify-string.h:301:25: error: call to ‘__write_overflow_field’ declared with attribute warning: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Werror=attribute-warning]
301 | __write_overflow_field(p_size_field, size);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This points to the memset() in uvc_register_video(). It is clear that
the argument to sizeof() is incorrect, as uvc->vdev (a 'struct
video_device') is being zeroed out but the size of uvc->video (a 'struct
uvc_video') is being used as the third arugment to memset().

pahole shows that prior to commit 9b91a6523078 ("usb: gadget: uvc:
increase worker prio to WQ_HIGHPRI"), 'struct video_device' and
'struct ucv_video' had the same size, meaning that the argument to
sizeof() is incorrect semantically but there is no visible issue:

$ pahole -s build/drivers/usb/gadget/function/f_uvc.o | grep -E "(uvc_video|video_device)\s+"
video_device 1400 4
uvc_video 1400 3

After that change, uvc_video becomes slightly larger, meaning that the
memset() will overwrite by 8 bytes:

$ pahole -s build/drivers/usb/gadget/function/f_uvc.o | grep -E "(uvc_video|video_device)\s+"
video_device 1400 4
uvc_video 1408 3

Fix the arugment to sizeof() so that there is no overwrite.

Cc: stable@vger.kernel.org
Fixes: e4ce9ed835bc ("usb: gadget: uvc: ensure the vdev is unset")
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20220928201921.3152163-1-nathan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/usb/gadget/function/f_uvc.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/usb/gadget/function/f_uvc.c
+++ b/drivers/usb/gadget/function/f_uvc.c
@@ -421,7 +421,7 @@ uvc_register_video(struct uvc_device *uv
int ret;

/* TODO reference counting. */
- memset(&uvc->vdev, 0, sizeof(uvc->video));
+ memset(&uvc->vdev, 0, sizeof(uvc->vdev));
uvc->vdev.v4l2_dev = &uvc->v4l2_dev;
uvc->vdev.v4l2_dev->dev = &cdev->gadget->dev;
uvc->vdev.fops = &uvc_v4l2_fops;