Hi Peilin, Thank you for the patch.
On Sun, Jul 26, 2020 at 12:44:39PM -0400, Peilin Ye wrote: > video_put_user() is copying uninitialized stack memory to userspace. Fix > it by initializing `vb32` using memset(). What makes you think this will fix the issue ? When initializing a structure at declaration time, the fields that are not explicitly specified should be initialized to 0 by the compiler. See https://www.ibm.com/support/knowledgecenter/en/SSLTBW_2.3.0/com.ibm.zos.v2r3.cbclx01/strin.htm: If a structure variable is partially initialized, all the uninitialized structure members are implicitly initialized to zero no matter what the storage class of the structure variable is. See the following example: struct one { int a; int b; int c; }; void main() { struct one z1; // Members in z1 do not have default initial values. static struct one z2; // z2.a=0, z2.b=0, and z2.c=0. struct one z3 = {1}; // z3.a=1, z3.b=0, and z3.c=0. } > Reported-and-tested-by: syzbot+79d751604cb6f29fb...@syzkaller.appspotmail.com > Link: https://syzkaller.appspot.com/bug?extid=79d751604cb6f29fbf59 > Signed-off-by: Peilin Ye <yepeilin...@gmail.com> > --- > drivers/media/v4l2-core/v4l2-ioctl.c | 32 +++++++++++++++------------- > 1 file changed, 17 insertions(+), 15 deletions(-) > > diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c > b/drivers/media/v4l2-core/v4l2-ioctl.c > index a556880f225a..08909f58dc80 100644 > --- a/drivers/media/v4l2-core/v4l2-ioctl.c > +++ b/drivers/media/v4l2-core/v4l2-ioctl.c > @@ -3210,21 +3210,23 @@ static int video_put_user(void __user *arg, void > *parg, unsigned int cmd) > case VIDIOC_DQBUF_TIME32: > case VIDIOC_PREPARE_BUF_TIME32: { > struct v4l2_buffer *vb = parg; > - struct v4l2_buffer_time32 vb32 = { > - .index = vb->index, > - .type = vb->type, > - .bytesused = vb->bytesused, > - .flags = vb->flags, > - .field = vb->field, > - .timestamp.tv_sec = vb->timestamp.tv_sec, > - .timestamp.tv_usec = vb->timestamp.tv_usec, > - .timecode = vb->timecode, > - .sequence = vb->sequence, > - .memory = vb->memory, > - .m.userptr = vb->m.userptr, > - .length = vb->length, > - .request_fd = vb->request_fd, > - }; > + struct v4l2_buffer_time32 vb32; > + > + memset(&vb32, 0, sizeof(vb32)); > + > + vb32.index = vb->index; > + vb32.type = vb->type; > + vb32.bytesused = vb->bytesused; > + vb32.flags = vb->flags; > + vb32.field = vb->field; > + vb32.timestamp.tv_sec = vb->timestamp.tv_sec; > + vb32.timestamp.tv_usec = vb->timestamp.tv_usec; > + vb32.timecode = vb->timecode; > + vb32.sequence = vb->sequence; > + vb32.memory = vb->memory; > + vb32.m.userptr = vb->m.userptr; > + vb32.length = vb->length; > + vb32.request_fd = vb->request_fd; > > if (copy_to_user(arg, &vb32, sizeof(vb32))) > return -EFAULT; -- Regards, Laurent Pinchart
