This patch is basically a port of Ørjan Eide's similar patch for ION https://lore.kernel.org/lkml/20200414134629.54567-1-orjan.eide@arm.com/
Only sync the sg-list of dma-buf heap attachment when the attachment is actually mapped on the device.
dma-bufs may be synced at any time. It can be reached from user space via DMA_BUF_IOCTL_SYNC, so there are no guarantees from callers on when syncs may be attempted, and dma_buf_end_cpu_access() and dma_buf_begin_cpu_access() may not be paired.
Since the sg_list's dma_address isn't set up until the buffer is used on the device, and dma_map_sg() is called on it, the dma_address will be NULL if sync is attempted on the dma-buf before it's mapped on a device.
Before v5.0 (commit 55897af63091 ("dma-direct: merge swiotlb_dma_ops into the dma_direct code")) this was a problem as the dma-api (at least the swiotlb_dma_ops on arm64) would use the potentially invalid dma_address. How that failed depended on how the device handled physical address 0. If 0 was a valid address to physical ram, that page would get flushed a lot, while the actual pages in the buffer would not get synced correctly. While if 0 is an invalid physical address it may cause a fault and trigger a crash.
In v5.0 this was incidentally fixed by commit 55897af63091 ("dma-direct: merge swiotlb_dma_ops into the dma_direct code"), as this moved the dma-api to use the page pointer in the sg_list, and (for Ion buffers at least) this will always be valid if the sg_list exists at all.
But, this issue is re-introduced in v5.3 with commit 449fa54d6815 ("dma-direct: correct the physical addr in dma_direct_sync_sg_for_cpu/device") moves the dma-api back to the old behaviour and picks the dma_address that may be invalid.
dma-buf core doesn't ensure that the buffer is mapped on the device, and thus have a valid sg_list, before calling the exporter's begin_cpu_access.
Logic and commit message originally by: Ørjan Eide orjan.eide@arm.com
Cc: Sumit Semwal sumit.semwal@linaro.org Cc: Liam Mark lmark@codeaurora.org Cc: Laura Abbott labbott@kernel.org Cc: Brian Starkey Brian.Starkey@arm.com Cc: Hridya Valsaraju hridya@google.com Cc: Suren Baghdasaryan surenb@google.com Cc: Sandeep Patil sspatil@google.com Cc: Ørjan Eide orjan.eide@arm.com Cc: Robin Murphy robin.murphy@arm.com Cc: Ezequiel Garcia ezequiel@collabora.com Cc: Simon Ser contact@emersion.fr Cc: James Jones jajones@nvidia.com Cc: linux-media@vger.kernel.org Cc: dri-devel@lists.freedesktop.org Signed-off-by: John Stultz john.stultz@linaro.org --- drivers/dma-buf/heaps/cma_heap.c | 10 ++++++++++ drivers/dma-buf/heaps/system_heap.c | 10 ++++++++++ 2 files changed, 20 insertions(+)
diff --git a/drivers/dma-buf/heaps/cma_heap.c b/drivers/dma-buf/heaps/cma_heap.c index 4f20f07872e5..e19320f52063 100644 --- a/drivers/dma-buf/heaps/cma_heap.c +++ b/drivers/dma-buf/heaps/cma_heap.c @@ -44,6 +44,7 @@ struct dma_heap_attachment { struct device *dev; struct sg_table table; struct list_head list; + bool mapped; };
static int cma_heap_attach(struct dma_buf *dmabuf, @@ -68,6 +69,7 @@ static int cma_heap_attach(struct dma_buf *dmabuf,
a->dev = attachment->dev; INIT_LIST_HEAD(&a->list); + a->mapped = false;
attachment->priv = a;
@@ -101,6 +103,7 @@ static struct sg_table *cma_heap_map_dma_buf(struct dma_buf_attachment *attachme if (!dma_map_sg(attachment->dev, table->sgl, table->nents, direction)) table = ERR_PTR(-ENOMEM); + a->mapped = true; return table; }
@@ -108,6 +111,9 @@ static void cma_heap_unmap_dma_buf(struct dma_buf_attachment *attachment, struct sg_table *table, enum dma_data_direction direction) { + struct dma_heap_attachment *a = attachment->priv; + + a->mapped = false; dma_unmap_sg(attachment->dev, table->sgl, table->nents, direction); }
@@ -122,6 +128,8 @@ static int cma_heap_dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
mutex_lock(&buffer->lock); list_for_each_entry(a, &buffer->attachments, list) { + if (!a->mapped) + continue; dma_sync_sg_for_cpu(a->dev, a->table.sgl, a->table.nents, direction); } @@ -141,6 +149,8 @@ static int cma_heap_dma_buf_end_cpu_access(struct dma_buf *dmabuf,
mutex_lock(&buffer->lock); list_for_each_entry(a, &buffer->attachments, list) { + if (!a->mapped) + continue; dma_sync_sg_for_device(a->dev, a->table.sgl, a->table.nents, direction); } diff --git a/drivers/dma-buf/heaps/system_heap.c b/drivers/dma-buf/heaps/system_heap.c index f30904345cce..c0d051203300 100644 --- a/drivers/dma-buf/heaps/system_heap.c +++ b/drivers/dma-buf/heaps/system_heap.c @@ -38,6 +38,7 @@ struct dma_heap_attachment { struct device *dev; struct sg_table *table; struct list_head list; + bool mapped; };
#define HIGH_ORDER_GFP (((GFP_HIGHUSER | __GFP_ZERO | __GFP_NOWARN \ @@ -94,6 +95,7 @@ static int system_heap_attach(struct dma_buf *dmabuf, a->table = table; a->dev = attachment->dev; INIT_LIST_HEAD(&a->list); + a->mapped = false;
attachment->priv = a;
@@ -128,6 +130,7 @@ static struct sg_table *system_heap_map_dma_buf(struct dma_buf_attachment *attac if (!dma_map_sg(attachment->dev, table->sgl, table->nents, direction)) return ERR_PTR(-ENOMEM);
+ a->mapped = true; return table; }
@@ -135,6 +138,9 @@ static void system_heap_unmap_dma_buf(struct dma_buf_attachment *attachment, struct sg_table *table, enum dma_data_direction direction) { + struct dma_heap_attachment *a = attachment->priv; + + a->mapped = false; dma_unmap_sg(attachment->dev, table->sgl, table->nents, direction); }
@@ -150,6 +156,8 @@ static int system_heap_dma_buf_begin_cpu_access(struct dma_buf *dmabuf, invalidate_kernel_vmap_range(buffer->vaddr, buffer->len);
list_for_each_entry(a, &buffer->attachments, list) { + if (!a->mapped) + continue; dma_sync_sg_for_cpu(a->dev, a->table->sgl, a->table->nents, direction); } @@ -170,6 +178,8 @@ static int system_heap_dma_buf_end_cpu_access(struct dma_buf *dmabuf, flush_kernel_vmap_range(buffer->vaddr, buffer->len);
list_for_each_entry(a, &buffer->attachments, list) { + if (!a->mapped) + continue; dma_sync_sg_for_device(a->dev, a->table->sgl, a->table->nents, direction); }