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dma-buf: avoid using IS_ERR_OR_NULL

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dma_buf_map_attachment and dma_buf_vmap can return NULL or
ERR_PTR on a error.  This encourages a common buggy pattern in
callers:
	sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
	if (IS_ERR_OR_NULL(sgt))
                return PTR_ERR(sgt);

This causes the caller to return 0 on an error.  IS_ERR_OR_NULL
is almost always a sign of poorly-defined error handling.

This patch converts dma_buf_map_attachment to always return
ERR_PTR, and fixes the callers that incorrectly handled NULL.
There are a few more callers that were not checking for NULL
at all, which would have dereferenced a NULL pointer later.
There are also a few more callers that correctly handled NULL
and ERR_PTR differently, I left those alone but they could also
be modified to delete the NULL check.

This patch also converts dma_buf_vmap to always return NULL.
All the callers to dma_buf_vmap only check for NULL, and would
have dereferenced an ERR_PTR and panic'd if one was ever
returned. This is not consistent with the rest of the dma buf
APIs, but matches the expectations of all of the callers.

Signed-off-by: Colin Cross <ccross@android.com>
Reviewed-by: Rob Clark <robdclark@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Colin Cross
2013-12-20 16:43:50 -08:00
committed by Greg Kroah-Hartman
parent 38dbfb59d1
commit fee0c54e28
4 changed files with 14 additions and 10 deletions
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18
drivers/base/dma-buf.c
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@@ -251,9 +251,8 @@ EXPORT_SYMBOL_GPL(dma_buf_put);
* @dmabuf: [in] buffer to attach device to.
* @dev: [in] device to be attached.
*
* Returns struct dma_buf_attachment * for this attachment; may return negative
* error codes.
*
* Returns struct dma_buf_attachment * for this attachment; returns ERR_PTR on
* error.
*/
struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
struct device *dev)
@@ -319,9 +318,8 @@ EXPORT_SYMBOL_GPL(dma_buf_detach);
* @attach: [in] attachment whose scatterlist is to be returned
* @direction: [in] direction of DMA transfer
*
* Returns sg_table containing the scatterlist to be returned; may return NULL
* or ERR_PTR.
*
* Returns sg_table containing the scatterlist to be returned; returns ERR_PTR
* on error.
*/
struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
enum dma_data_direction direction)
@@ -334,6 +332,8 @@ struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
return ERR_PTR(-EINVAL);
sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
if (!sg_table)
sg_table = ERR_PTR(-ENOMEM);
return sg_table;
}
@@ -544,6 +544,8 @@ EXPORT_SYMBOL_GPL(dma_buf_mmap);
* These calls are optional in drivers. The intended use for them
* is for mapping objects linear in kernel space for high use objects.
* Please attempt to use kmap/kunmap before thinking about these interfaces.
*
* Returns NULL on error.
*/
void *dma_buf_vmap(struct dma_buf *dmabuf)
{
@@ -566,7 +568,9 @@ void *dma_buf_vmap(struct dma_buf *dmabuf)
BUG_ON(dmabuf->vmap_ptr);
ptr = dmabuf->ops->vmap(dmabuf);
if (IS_ERR_OR_NULL(ptr))
if (WARN_ON_ONCE(IS_ERR(ptr)))
ptr = NULL;
if (!ptr)
goto out_unlock;
dmabuf->vmap_ptr = ptr;