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SubjectRe: [PATCH] dma-buf: simplified calling conventions for dma_buf_fd()
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On 05/22/2018 01:09 AM, Jens Wiklander wrote:
> From: Al Viro <viro@zeniv.linux.org.uk>
>
> Make dma_buf_fd() drop the file reference on failure, folding
> dma_buf_put() into it.
>
> Users of dma_buf_fd() (drm, videobuf2, ion and tee) are updated to take
> the new calling convention into account.
>

For the Ion portion,

Acked-by: Laura Abbott <labbott@redhat.com>

> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
> [jw: rebased and updated commit message]
> Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>
> ---
>
> I received this patch as a response to what has become
> bb765d1c331f ("tee: shm: fix use-after-free via temporarily dropped reference")
>
> drivers/dma-buf/dma-buf.c | 16 +++++----
> drivers/gpu/drm/drm_prime.c | 15 +++-----
> drivers/gpu/drm/i915/gvt/dmabuf.c | 4 +--
> drivers/gpu/drm/ttm/ttm_object.c | 3 +-
> .../media/common/videobuf2/videobuf2-core.c | 14 ++++----
> drivers/staging/android/ion/ion.c | 7 +---
> drivers/tee/tee_core.c | 35 ++++++-------------
> drivers/tee/tee_shm.c | 8 +----
> 8 files changed, 36 insertions(+), 66 deletions(-)
>
> diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
> index d78d5fc173dc..78981928758e 100644
> --- a/drivers/dma-buf/dma-buf.c
> +++ b/drivers/dma-buf/dma-buf.c
> @@ -471,17 +471,21 @@ EXPORT_SYMBOL_GPL(dma_buf_export);
> */
> int dma_buf_fd(struct dma_buf *dmabuf, int flags)
> {
> + struct file *file;
> int fd;
>
> - if (!dmabuf || !dmabuf->file)
> + if (!dmabuf)
> return -EINVAL;
>
> - fd = get_unused_fd_flags(flags);
> - if (fd < 0)
> - return fd;
> -
> - fd_install(fd, dmabuf->file);
> + file = dmabuf->file;
> + if (!file)
> + return -EINVAL;
>
> + fd = get_unused_fd_flags(flags);
> + if (fd >= 0)
> + fd_install(fd, file);
> + else
> + fput(file);
> return fd;
> }
> EXPORT_SYMBOL_GPL(dma_buf_fd);
> diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
> index 7856a9b3f8a8..06d1b7d3751a 100644
> --- a/drivers/gpu/drm/drm_prime.c
> +++ b/drivers/gpu/drm/drm_prime.c
> @@ -662,8 +662,10 @@ int drm_gem_prime_handle_to_fd(struct drm_device *dev,
> ret = drm_prime_add_buf_handle(&file_priv->prime,
> dmabuf, handle);
> mutex_unlock(&dev->object_name_lock);
> - if (ret)
> - goto fail_put_dmabuf;
> + if (unlikely(ret)) {
> + dma_buf_put(dmabuf);
> + goto out;
> + }
>
> out_have_handle:
> ret = dma_buf_fd(dmabuf, flags);
> @@ -673,17 +675,10 @@ int drm_gem_prime_handle_to_fd(struct drm_device *dev,
> * and that is invariant as long as a userspace gem handle exists.
> * Closing the handle will clean out the cache anyway, so we don't leak.
> */
> - if (ret < 0) {
> - goto fail_put_dmabuf;
> - } else {
> + if (ret >= 0) {
> *prime_fd = ret;
> ret = 0;
> }
> -
> - goto out;
> -
> -fail_put_dmabuf:
> - dma_buf_put(dmabuf);
> out:
> drm_gem_object_put_unlocked(obj);
> out_unlock:
> diff --git a/drivers/gpu/drm/i915/gvt/dmabuf.c b/drivers/gpu/drm/i915/gvt/dmabuf.c
> index 6f4f8e941fc2..1783c724d96c 100644
> --- a/drivers/gpu/drm/i915/gvt/dmabuf.c
> +++ b/drivers/gpu/drm/i915/gvt/dmabuf.c
> @@ -479,7 +479,7 @@ int intel_vgpu_get_dmabuf(struct intel_vgpu *vgpu, unsigned int dmabuf_id)
> ret = dma_buf_fd(dmabuf, DRM_CLOEXEC | DRM_RDWR);
> if (ret < 0) {
> gvt_vgpu_err("create dma-buf fd failed ret:%d\n", ret);
> - goto out_free_dmabuf;
> + goto out_free_gem;
> }
> dmabuf_fd = ret;
>
> @@ -502,8 +502,6 @@ int intel_vgpu_get_dmabuf(struct intel_vgpu *vgpu, unsigned int dmabuf_id)
>
> return dmabuf_fd;
>
> -out_free_dmabuf:
> - dma_buf_put(dmabuf);
> out_free_gem:
> i915_gem_object_put(obj);
> out:
> diff --git a/drivers/gpu/drm/ttm/ttm_object.c b/drivers/gpu/drm/ttm/ttm_object.c
> index 1aa2baa83959..30d29d17653f 100644
> --- a/drivers/gpu/drm/ttm/ttm_object.c
> +++ b/drivers/gpu/drm/ttm/ttm_object.c
> @@ -730,8 +730,7 @@ int ttm_prime_handle_to_fd(struct ttm_object_file *tfile,
> if (ret >= 0) {
> *prime_fd = ret;
> ret = 0;
> - } else
> - dma_buf_put(dma_buf);
> + }
>
> out_unref:
> if (base)
> diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
> index d3f7bb33a54d..3baf689241cc 100644
> --- a/drivers/media/common/videobuf2/videobuf2-core.c
> +++ b/drivers/media/common/videobuf2/videobuf2-core.c
> @@ -1881,15 +1881,13 @@ int vb2_core_expbuf(struct vb2_queue *q, int *fd, unsigned int type,
> if (ret < 0) {
> dprintk(3, "buffer %d, plane %d failed to export (%d)\n",
> index, plane, ret);
> - dma_buf_put(dbuf);
> - return ret;
> + } else {
> + dprintk(3, "buffer %d, plane %d exported as %d descriptor\n",
> + index, plane, ret);
> + *fd = ret;
> + ret = 0;
> }
> -
> - dprintk(3, "buffer %d, plane %d exported as %d descriptor\n",
> - index, plane, ret);
> - *fd = ret;
> -
> - return 0;
> + return ret;
> }
> EXPORT_SYMBOL_GPL(vb2_core_expbuf);
>
> diff --git a/drivers/staging/android/ion/ion.c b/drivers/staging/android/ion/ion.c
> index e74db7902549..c9fcb2a2f518 100644
> --- a/drivers/staging/android/ion/ion.c
> +++ b/drivers/staging/android/ion/ion.c
> @@ -381,7 +381,6 @@ int ion_alloc(size_t len, unsigned int heap_id_mask, unsigned int flags)
> struct ion_buffer *buffer = NULL;
> struct ion_heap *heap;
> DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
> - int fd;
> struct dma_buf *dmabuf;
>
> pr_debug("%s: len %zu heap_id_mask %u flags %x\n", __func__,
> @@ -425,11 +424,7 @@ int ion_alloc(size_t len, unsigned int heap_id_mask, unsigned int flags)
> return PTR_ERR(dmabuf);
> }
>
> - fd = dma_buf_fd(dmabuf, O_CLOEXEC);
> - if (fd < 0)
> - dma_buf_put(dmabuf);
> -
> - return fd;
> + return dma_buf_fd(dmabuf, O_CLOEXEC);
> }
>
> int ion_query_heaps(struct ion_heap_query *query)
> diff --git a/drivers/tee/tee_core.c b/drivers/tee/tee_core.c
> index dd46b758852a..1cb54f6f3c6a 100644
> --- a/drivers/tee/tee_core.c
> +++ b/drivers/tee/tee_core.c
> @@ -125,7 +125,6 @@ static int tee_ioctl_version(struct tee_context *ctx,
> static int tee_ioctl_shm_alloc(struct tee_context *ctx,
> struct tee_ioctl_shm_alloc_data __user *udata)
> {
> - long ret;
> struct tee_ioctl_shm_alloc_data data;
> struct tee_shm *shm;
>
> @@ -144,25 +143,18 @@ static int tee_ioctl_shm_alloc(struct tee_context *ctx,
> data.flags = shm->flags;
> data.size = shm->size;
>
> - if (copy_to_user(udata, &data, sizeof(data)))
> - ret = -EFAULT;
> - else
> - ret = tee_shm_get_fd(shm);
> + if (unlikely(copy_to_user(udata, &data, sizeof(data)))) {
> + tee_shm_put(shm);
> + return -EFAULT;
> + }
>
> - /*
> - * When user space closes the file descriptor the shared memory
> - * should be freed or if tee_shm_get_fd() failed then it will
> - * be freed immediately.
> - */
> - tee_shm_put(shm);
> - return ret;
> + return tee_shm_get_fd(shm);
> }
>
> static int
> tee_ioctl_shm_register(struct tee_context *ctx,
> struct tee_ioctl_shm_register_data __user *udata)
> {
> - long ret;
> struct tee_ioctl_shm_register_data data;
> struct tee_shm *shm;
>
> @@ -182,17 +174,12 @@ tee_ioctl_shm_register(struct tee_context *ctx,
> data.flags = shm->flags;
> data.length = shm->size;
>
> - if (copy_to_user(udata, &data, sizeof(data)))
> - ret = -EFAULT;
> - else
> - ret = tee_shm_get_fd(shm);
> - /*
> - * When user space closes the file descriptor the shared memory
> - * should be freed or if tee_shm_get_fd() failed then it will
> - * be freed immediately.
> - */
> - tee_shm_put(shm);
> - return ret;
> + if (unlikely(copy_to_user(udata, &data, sizeof(data)))) {
> + tee_shm_put(shm);
> + return -EFAULT;
> + }
> +
> + return tee_shm_get_fd(shm);
> }
>
> static int params_from_user(struct tee_context *ctx, struct tee_param *params,
> diff --git a/drivers/tee/tee_shm.c b/drivers/tee/tee_shm.c
> index 07d3be6f0780..53b35b5e5776 100644
> --- a/drivers/tee/tee_shm.c
> +++ b/drivers/tee/tee_shm.c
> @@ -355,16 +355,10 @@ EXPORT_SYMBOL_GPL(tee_shm_register);
> */
> int tee_shm_get_fd(struct tee_shm *shm)
> {
> - int fd;
> -
> if (!(shm->flags & TEE_SHM_DMA_BUF))
> return -EINVAL;
>
> - get_dma_buf(shm->dmabuf);
> - fd = dma_buf_fd(shm->dmabuf, O_CLOEXEC);
> - if (fd < 0)
> - dma_buf_put(shm->dmabuf);
> - return fd;
> + return dma_buf_fd(shm->dmabuf, O_CLOEXEC);
> }
>
> /**
>

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