From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from galahad.ideasonboard.com ([185.26.127.97]:48152 "EHLO galahad.ideasonboard.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751796AbaHWRO3 (ORCPT ); Sat, 23 Aug 2014 13:14:29 -0400 From: Laurent Pinchart To: Hans Verkuil Cc: LMML , Jan Kara , m.szyprowski@samsung.com, pawel@osciak.com Subject: Re: [PATCHv2] videobuf2-core: take mmap_sem before calling __qbuf_userptr Date: Sat, 23 Aug 2014 19:15:09 +0200 Message-ID: <5303867.CVmOHk9ueU@avalon> In-Reply-To: <53F7D2D3.4070809@xs4all.nl> References: <53F7D2D3.4070809@xs4all.nl> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: linux-media-owner@vger.kernel.org List-ID: Hi Hans, Thank you for the patch. On Friday 22 August 2014 23:31:31 Hans Verkuil wrote: > (Changes since v1: fix the embarrassing bug where mmap_sem wasn't > initialized) > > Commit f035eb4e976ef5a059e30bc91cfd310ff030a7d3 (videobuf2: fix lockdep > warning) unfortunately removed the mmap_sem lock that is needed around the > call to __qbuf_userptr. Amazingly nobody noticed this (especially me as the > author) until Jan Kara pointed this out to me. > > Signed-off-by: Hans Verkuil > Reported-by: Jan Kara Acked-by: Laurent Pinchart but please see below for one small comment. > --- > drivers/media/v4l2-core/videobuf2-core.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/drivers/media/v4l2-core/videobuf2-core.c > b/drivers/media/v4l2-core/videobuf2-core.c index 5b808e2..a0ab6af 100644 > --- a/drivers/media/v4l2-core/videobuf2-core.c > +++ b/drivers/media/v4l2-core/videobuf2-core.c > @@ -1591,6 +1591,7 @@ static void __enqueue_in_driver(struct vb2_buffer *vb) > static int __buf_prepare(struct vb2_buffer *vb, const struct v4l2_buffer > *b) { > struct vb2_queue *q = vb->vb2_queue; > + struct rw_semaphore *mmap_sem; Do we really need the local variable ? > int ret; > > ret = __verify_length(vb, b); > @@ -1627,7 +1628,10 @@ static int __buf_prepare(struct vb2_buffer *vb, const > struct v4l2_buffer *b) ret = __qbuf_mmap(vb, b); > break; > case V4L2_MEMORY_USERPTR: > + mmap_sem = ¤t->mm->mmap_sem; > + down_read(mmap_sem); > ret = __qbuf_userptr(vb, b); > + up_read(mmap_sem); > break; > case V4L2_MEMORY_DMABUF: > ret = __qbuf_dmabuf(vb, b); -- Regards, Laurent Pinchart