The Documentation/DMA-API-HOWTO.txt states that dma_map_sg returns the numer of the created entries in the DMA address space. However the subsequent calls to dma_sync_sg_for_{device,cpu} and dma_unmap_sg must be called with the original number of entries passed to dma_map_sg. The sg_table->nents in turn holds the result of the dma_map_sg call as stated in include/linux/scatterlist.h. Adapt the code to obey those rules.
Signed-off-by: Marek Szyprowski m.szyprowski@samsung.com --- For more information, see '[PATCH v2 00/21] DRM: fix struct sg_table nents vs. orig_nents misuse' thread: https://lkml.org/lkml/2020/5/4/373 --- drivers/dma-buf/heaps/heap-helpers.c | 7 ++++--- drivers/dma-buf/udmabuf.c | 5 +++-- 2 files changed, 7 insertions(+), 5 deletions(-)
diff --git a/drivers/dma-buf/heaps/heap-helpers.c b/drivers/dma-buf/heaps/heap-helpers.c index 9f964ca..b923863 100644 --- a/drivers/dma-buf/heaps/heap-helpers.c +++ b/drivers/dma-buf/heaps/heap-helpers.c @@ -144,8 +144,9 @@ struct sg_table *dma_heap_map_dma_buf(struct dma_buf_attachment *attachment,
table = &a->table;
- if (!dma_map_sg(attachment->dev, table->sgl, table->nents, - direction)) + table->nents = dma_map_sg(attachment->dev, table->sgl, + table->orig_nents, direction); + if (!table->nents) table = ERR_PTR(-ENOMEM); return table; } @@ -154,7 +155,7 @@ static void dma_heap_unmap_dma_buf(struct dma_buf_attachment *attachment, struct sg_table *table, enum dma_data_direction direction) { - dma_unmap_sg(attachment->dev, table->sgl, table->nents, direction); + dma_unmap_sg(attachment->dev, table->sgl, table->orig_nents, direction); }
static vm_fault_t dma_heap_vm_fault(struct vm_fault *vmf) diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c index acb26c6..ea0cf71 100644 --- a/drivers/dma-buf/udmabuf.c +++ b/drivers/dma-buf/udmabuf.c @@ -63,7 +63,8 @@ static struct sg_table *get_sg_table(struct device *dev, struct dma_buf *buf, GFP_KERNEL); if (ret < 0) goto err; - if (!dma_map_sg(dev, sg->sgl, sg->nents, direction)) { + sg->nents = dma_map_sg(dev, sg->sgl, sg->orig_nents, direction); + if (!sg->nents) { ret = -EINVAL; goto err; } @@ -78,7 +79,7 @@ static struct sg_table *get_sg_table(struct device *dev, struct dma_buf *buf, static void put_sg_table(struct device *dev, struct sg_table *sg, enum dma_data_direction direction) { - dma_unmap_sg(dev, sg->sgl, sg->nents, direction); + dma_unmap_sg(dev, sg->sgl, sg->orig_nents, direction); sg_free_table(sg); kfree(sg); }