Hi Nathan,

Thank you for the patch.

On Wed, Sep 28, 2022 at 01:19:21PM -0700, Nathan Chancellor wrote:

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

Good catch.

Reviewed-by: Laurent Pinchart laurent.pinchart@ideasonboard.com

---

drivers/usb/gadget/function/f_uvc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/gadget/function/f_uvc.c b/drivers/usb/gadget/function/f_uvc.c index 71669e0e4d00..86bb0098fb66 100644 --- 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 *uvc) 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;

base-commit: f76349cf41451c5c42a99f18a9163377e4b364ff