firewire: core: fix DMA mapping direction

Seen with recent libdc1394:  If a client mmap()s the buffer of an
isochronous reception buffer with PROT_READ|PROT_WRITE instead of just
PROT_READ, firewire-core sets the wrong DMA mapping direction during
buffer initialization.

The fix is to split fw_iso_buffer_init() into allocation and DMA mapping
and to perform the latter after both buffer and DMA context were
allocated.  Buffer allocation and context allocation may happen in any
order, but we need the context type (reception or transmission) in order
to set the DMA direction of the buffer.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

1 files changed, 52 insertions, 28 deletions

diff --git a/drivers/firewire/core-iso.c b/drivers/firewire/core-iso.c
index d156582..8382e27 100644
--- a/drivers/firewire/core-iso.c
+++ b/drivers/firewire/core-iso.c
@@ -39,52 +39,73 @@
  * Isochronous DMA context management
  */
 
-int fw_iso_buffer_init(struct fw_iso_buffer *buffer, struct fw_card *card,
-		       int page_count, enum dma_data_direction direction)
+int fw_iso_buffer_alloc(struct fw_iso_buffer *buffer, int page_count)
 {
-	int i, j;
-	dma_addr_t address;
-
-	buffer->page_count = page_count;
-	buffer->direction = direction;
+	int i;
 
+	buffer->page_count = 0;
+	buffer->page_count_mapped = 0;
 	buffer->pages = kmalloc(page_count * sizeof(buffer->pages[0]),
 				GFP_KERNEL);
 	if (buffer->pages == NULL)
-		goto out;
+		return -ENOMEM;
 
-	for (i = 0; i < buffer->page_count; i++) {
+	for (i = 0; i < page_count; i++) {
 		buffer->pages[i] = alloc_page(GFP_KERNEL | GFP_DMA32 | __GFP_ZERO);
 		if (buffer->pages[i] == NULL)
-			goto out_pages;
+			break;
+	}
+	buffer->page_count = i;
+	if (i < page_count) {
+		fw_iso_buffer_destroy(buffer, NULL);
+		return -ENOMEM;
+	}
 
+	return 0;
+}
+
+int fw_iso_buffer_map_dma(struct fw_iso_buffer *buffer, struct fw_card *card,
+			  enum dma_data_direction direction)
+{
+	dma_addr_t address;
+	int i;
+
+	buffer->direction = direction;
+
+	for (i = 0; i < buffer->page_count; i++) {
 		address = dma_map_page(card->device, buffer->pages[i],
 				       0, PAGE_SIZE, direction);
-		if (dma_mapping_error(card->device, address)) {
-			__free_page(buffer->pages[i]);
-			goto out_pages;
-		}
+		if (dma_mapping_error(card->device, address))
+			break;
+
 		set_page_private(buffer->pages[i], address);
 	}
+	buffer->page_count_mapped = i;
+	if (i < buffer->page_count)
+		return -ENOMEM;
 
 	return 0;
+}
 
- out_pages:
-	for (j = 0; j < i; j++) {
-		address = page_private(buffer->pages[j]);
-		dma_unmap_page(card->device, address,
-			       PAGE_SIZE, direction);
-		__free_page(buffer->pages[j]);
-	}
-	kfree(buffer->pages);
- out:
-	buffer->pages = NULL;
+int fw_iso_buffer_init(struct fw_iso_buffer *buffer, struct fw_card *card,
+		       int page_count, enum dma_data_direction direction)
+{
+	int ret;
+
+	ret = fw_iso_buffer_alloc(buffer, page_count);
+	if (ret < 0)
+		return ret;
+
+	ret = fw_iso_buffer_map_dma(buffer, card, direction);
+	if (ret < 0)
+		fw_iso_buffer_destroy(buffer, card);
 
-	return -ENOMEM;
+	return ret;
 }
 EXPORT_SYMBOL(fw_iso_buffer_init);
 
-int fw_iso_buffer_map(struct fw_iso_buffer *buffer, struct vm_area_struct *vma)
+int fw_iso_buffer_map_vma(struct fw_iso_buffer *buffer,
+			  struct vm_area_struct *vma)
 {
 	unsigned long uaddr;
 	int i, err;
@@ -107,15 +128,18 @@ void fw_iso_buffer_destroy(struct fw_iso_buffer *buffer,
 	int i;
 	dma_addr_t address;
 
-	for (i = 0; i < buffer->page_count; i++) {
+	for (i = 0; i < buffer->page_count_mapped; i++) {
 		address = page_private(buffer->pages[i]);
 		dma_unmap_page(card->device, address,
 			       PAGE_SIZE, buffer->direction);
-		__free_page(buffer->pages[i]);
 	}
+	for (i = 0; i < buffer->page_count; i++)
+		__free_page(buffer->pages[i]);
 
 	kfree(buffer->pages);
 	buffer->pages = NULL;
+	buffer->page_count = 0;
+	buffer->page_count_mapped = 0;
 }
 EXPORT_SYMBOL(fw_iso_buffer_destroy);