[PATCH] dma-mapping: Lift address space checks out of debug code

[Kees Cook <keescook@chromium.org>]

As we've seen from USB and other areas, we need to always do runtime
checks for DMA operating on memory regions that might be remapped. This
consolidates the (existing!) checks and makes them on by default. A
warning will be triggered for any drivers still using DMA on the stack
(as has been seen in a few recent reports).

Suggested-by: Laura Abbott <labbott@redhat.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 include/linux/dma-debug.h   |  8 --------
 include/linux/dma-mapping.h |  8 +++++++-
 kernel/dma/debug.c          | 16 ----------------
 3 files changed, 7 insertions(+), 25 deletions(-)

diff --git a/include/linux/dma-debug.h b/include/linux/dma-debug.h
index 4208f94d93f7..2af9765d9af7 100644
--- a/include/linux/dma-debug.h
+++ b/include/linux/dma-debug.h
@@ -18,9 +18,6 @@ struct bus_type;
 
 extern void dma_debug_add_bus(struct bus_type *bus);
 
-extern void debug_dma_map_single(struct device *dev, const void *addr,
-				 unsigned long len);
-
 extern void debug_dma_map_page(struct device *dev, struct page *page,
 			       size_t offset, size_t size,
 			       int direction, dma_addr_t dma_addr);
@@ -75,11 +72,6 @@ static inline void dma_debug_add_bus(struct bus_type *bus)
 {
 }
 
-static inline void debug_dma_map_single(struct device *dev, const void *addr,
-					unsigned long len)
-{
-}
-
 static inline void debug_dma_map_page(struct device *dev, struct page *page,
 				      size_t offset, size_t size,
 				      int direction, dma_addr_t dma_addr)
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index 4a1c4fca475a..2d6b8382eab1 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -583,7 +583,13 @@ static inline unsigned long dma_get_merge_boundary(struct device *dev)
 static inline dma_addr_t dma_map_single_attrs(struct device *dev, void *ptr,
 		size_t size, enum dma_data_direction dir, unsigned long attrs)
 {
-	debug_dma_map_single(dev, ptr, size);
+	/* DMA must never operate on stack or other remappable places. */
+	WARN_ONCE(is_vmalloc_addr(ptr) || !virt_addr_valid(ptr),
+		"%s %s: driver maps %lu bytes from %s area\n",
+		dev ? dev_driver_string(dev) : "unknown driver",
+		dev ? dev_name(dev) : "unknown device", size,
+		is_vmalloc_addr(ptr) ? "vmalloc" : "invalid");
+
 	return dma_map_page_attrs(dev, virt_to_page(ptr), offset_in_page(ptr),
 			size, dir, attrs);
 }
diff --git a/kernel/dma/debug.c b/kernel/dma/debug.c
index 099002d84f46..aa1e6a1990b2 100644
--- a/kernel/dma/debug.c
+++ b/kernel/dma/debug.c
@@ -1232,22 +1232,6 @@ static void check_sg_segment(struct device *dev, struct scatterlist *sg)
 #endif
 }
 
-void debug_dma_map_single(struct device *dev, const void *addr,
-			    unsigned long len)
-{
-	if (unlikely(dma_debug_disabled()))
-		return;
-
-	if (!virt_addr_valid(addr))
-		err_printk(dev, NULL, "device driver maps memory from invalid area [addr=%p] [len=%lu]\n",
-			   addr, len);
-
-	if (is_vmalloc_addr(addr))
-		err_printk(dev, NULL, "device driver maps memory from vmalloc area [addr=%p] [len=%lu]\n",
-			   addr, len);
-}
-EXPORT_SYMBOL(debug_dma_map_single);
-
 void debug_dma_map_page(struct device *dev, struct page *page, size_t offset,
 			size_t size, int direction, dma_addr_t dma_addr)
 {
-- 
2.17.1


-- 
Kees Cook
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