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Mon, 12 Oct 2020 01:52:04 -0700 (PDT) From: "=?UTF-8?q?Christian=20K=C3=B6nig?=" X-Google-Original-From: =?UTF-8?q?Christian=20K=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 Subject: [PATCH 1/2] mm: mmap: fix fput in error path v2 Date: Mon, 12 Oct 2020 10:52:02 +0200 Message-Id: <20201012085203.56119-1-christian.koenig@amd.com> X-Mailer: git-send-email 2.17.1 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 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: 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 v= m_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, unsign= ed 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); --=20 2.17.1