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([2a02:908:1252:fb60:be8a:bd56:1f94:86e7]) by smtp.gmail.com with ESMTPSA id f25sm600558edr.53.2020.11.04.00.03.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 04 Nov 2020 00:03:18 -0800 (PST) Subject: Re: [PATCH 1/2] mm: mmap: fix fput in error path v2 From: =?UTF-8?Q?Christian_K=c3=b6nig?= To: akpm@linux-foundation.org, 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, daniel@ffwll.ch, sumit.semwal@linaro.org, willy@infradead.org, jhubbard@nvidia.com, jgg@ziepe.ca, linmiaohe@huawei.com References: <20201012085203.56119-1-christian.koenig@amd.com> Message-ID: Date: Wed, 4 Nov 2020 09:03:15 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20201012085203.56119-1-christian.koenig@amd.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US 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: If nobody comes up with an objections I'm going to merge that through=20 drm-misc-next. Thanks, Christian. Am 12.10.20 um 10:52 schrieb Christian K=C3=B6nig: > Patch "495c10cc1c0c CHROMIUM: dma-buf: restore args..." > adds a workaround for a bug in mmap_region. > > As the comment states ->mmap() callback can change > vma->vm_file and so we might call fput() on the wrong file. > > Revert the workaround and proper fix this in mmap_region. > > v2: drop the extra if in dma_buf_mmap as well > > Signed-off-by: Christian K=C3=B6nig > Reviewed-by: Jason Gunthorpe > --- > drivers/dma-buf/dma-buf.c | 20 +++----------------- > mm/mmap.c | 2 +- > 2 files changed, 4 insertions(+), 18 deletions(-) > > diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c > index a6ba4d598f0e..08630d057cf2 100644 > --- a/drivers/dma-buf/dma-buf.c > +++ 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 +1160,11 @@ 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; > + fput(vma->vm_file); > + vma->vm_file =3D get_file(dmabuf->file); > vma->vm_pgoff =3D pgoff; > =20 > - ret =3D dmabuf->ops->mmap(dmabuf, vma); > - if (ret) { > - /* restore old parameters on failure */ > - vma->vm_file =3D oldfile; > - fput(dmabuf->file); > - } else { > - if (oldfile) > - fput(oldfile); > - } > - return ret; > - > + return dmabuf->ops->mmap(dmabuf, vma); > } > EXPORT_SYMBOL_GPL(dma_buf_mmap); > =20 > diff --git a/mm/mmap.c b/mm/mmap.c > index 40248d84ad5f..3a2670d73355 100644 > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -1852,8 +1852,8 @@ unsigned long mmap_region(struct file *file, unsi= gned long addr, > return addr; > =20 > unmap_and_free_vma: > + fput(vma->vm_file); > vma->vm_file =3D NULL; > - fput(file); > =20 > /* Undo any partial mapping done by a device driver. */ > unmap_region(mm, vma, prev, vma->vm_start, vma->vm_end);