From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from cantor2.suse.de ([195.135.220.15]:39036 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932653AbaHZJJR (ORCPT ); Tue, 26 Aug 2014 05:09:17 -0400 Date: Tue, 26 Aug 2014 11:09:13 +0200 From: Jan Kara To: Hans Verkuil Cc: LMML , Jan Kara , Laurent Pinchart , m.szyprowski@samsung.com, pawel@osciak.com Subject: Re: [PATCHv2] videobuf2-core: take mmap_sem before calling __qbuf_userptr Message-ID: <20140826090913.GC1581@quack.suse.cz> References: <53F7D2D3.4070809@xs4all.nl> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <53F7D2D3.4070809@xs4all.nl> Sender: linux-media-owner@vger.kernel.org List-ID: On Fri 22-08-14 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 The patch looks good to me. You can add: Reviewed-by: Jan Kara Honza > --- > 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; > 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); > -- > 2.0.1 > -- Jan Kara SUSE Labs, CR