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[156.34.48.30]) by smtp.gmail.com with ESMTPSA id s123sm6228708qkd.128.2020.10.09.08.15.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 09 Oct 2020 08:15:40 -0700 (PDT) Received: from jgg by mlx with local (Exim 4.94) (envelope-from ) id 1kQu7Q-0020Yl-8k; Fri, 09 Oct 2020 12:15:40 -0300 Date: Fri, 9 Oct 2020 12:15:40 -0300 From: Jason Gunthorpe To: Christian =?utf-8?B?S8O2bmln?= Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linaro-mm-sig@lists.linaro.org, dri-devel@lists.freedesktop.org, linux-media@vger.kernel.org, chris@chris-wilson.co.uk, airlied@redhat.com, akpm@linux-foundation.org, daniel@ffwll.ch, sumit.semwal@linaro.org, willy@infradead.org, jhubbard@nvidia.com Subject: Re: [PATCH 1/6] mm: mmap: fix fput in error path Message-ID: <20201009151540.GX5177@ziepe.ca> References: <20201009150342.1979-1-christian.koenig@amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20201009150342.1979-1-christian.koenig@amd.com> Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Oct 09, 2020 at 05:03:37PM +0200, Christian K=C3=B6nig wrote: > Patch "495c10cc1c0c CHROMIUM: dma-buf: restore args..." > adds a workaround for a bug in mmap_region. >=20 > As the comment states ->mmap() callback can change > vma->vm_file and so we might call fput() on the wrong file. >=20 > Revert the workaround and proper fix this in mmap_region. >=20 > Signed-off-by: Christian K=C3=B6nig > drivers/dma-buf/dma-buf.c | 22 +++++----------------- > mm/mmap.c | 2 +- > 2 files changed, 6 insertions(+), 18 deletions(-) >=20 > diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c > index a6ba4d598f0e..edd57402a48a 100644 > +++ b/drivers/dma-buf/dma-buf.c > @@ -1143,9 +1143,6 @@ EXPORT_SYMBOL_GPL(dma_buf_end_cpu_access); > int dma_buf_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma, > unsigned long pgoff) > { > - struct file *oldfile; > - int ret; > - > if (WARN_ON(!dmabuf || !vma)) > return -EINVAL; > =20 > @@ -1163,22 +1160,13 @@ int dma_buf_mmap(struct dma_buf *dmabuf, struct= vm_area_struct *vma, > return -EINVAL; > =20 > /* readjust the vma */ > - get_file(dmabuf->file); > - oldfile =3D vma->vm_file; > - vma->vm_file =3D dmabuf->file; > - vma->vm_pgoff =3D pgoff; > + if (vma->vm_file) > + fput(vma->vm_file); This if is redundant too But otherwise Reviewed-by: Jason Gunthorpe Thanks, Jason