[PATCH] dma-mapping: do not mapping module memory

[PATCH] dma-mapping: do not mapping module memory

[lijiazi]

On ARM, x86_64, sparc64 platform, virt_to_page only convert a
_valid_ virtual address to struct page *, virt_addr_valid(x)
indicates whether a virtual address is valid. If ptr is point
to a static variable in module area, virt_to_page will return
a invalid value.

Signed-off-by: lijiazi <lijiazi@xiaomi.com>
---
 include/linux/dma-mapping.h | 10 +++++++---
 mm/vmalloc.c                |  1 +
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index 330ad58..37e645d 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -580,9 +580,13 @@ 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)
 {
-	/* DMA must never operate on areas that might be remapped. */
-	if (dev_WARN_ONCE(dev, is_vmalloc_addr(ptr),
-			  "rejecting DMA map of vmalloc memory\n"))
+	/* DMA must never operate on areas that might be remapped.
+	 * ARM, X86_64, sparc64 put module in a special place, if ptr
+	 * point to static variable in module area, virt_to_page will
+	 * return err page *.
+	 */
+	if (dev_WARN_ONCE(dev, is_vmalloc_or_module_addr(ptr),
+			  "rejecting DMA map of vmalloc or module memory\n"))
 		return DMA_MAPPING_ERROR;
 	debug_dma_map_single(dev, ptr, size);
 	return dma_map_page_attrs(dev, virt_to_page(ptr), offset_in_page(ptr),
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 588303a..71ce6dc 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -262,6 +262,7 @@ int is_vmalloc_or_module_addr(const void *x)
 #endif
 	return is_vmalloc_addr(x);
 }
+EXPORT_SYMBOL(is_vmalloc_or_module_addr);
 
 /*
  * Walk a vmap address to the struct page it maps.
-- 
2.7.4

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Re: [PATCH] dma-mapping: do not mapping module memory

[Christoph Hellwig]

On Fri, Nov 29, 2019 at 07:03:40PM +0800, lijiazi wrote:
> On ARM, x86_64, sparc64 platform, virt_to_page only convert a
> _valid_ virtual address to struct page *, virt_addr_valid(x)
> indicates whether a virtual address is valid. If ptr is point
> to a static variable in module area, virt_to_page will return
> a invalid value.

While the path isn't wrong, why bother? 
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