dma-direct: Fix potential NULL pointer dereference

When booting the kernel v5.9-rc4 on a VM, the kernel would panic when
printing a warning message in swiotlb_map(). The dev->dma_mask must not
be a NULL pointer when calling the dma mapping layer. A NULL pointer
check can potentially avoid the panic.

Signed-off-by: Thomas Tai <thomas.tai@oracle.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

diff --git a/include/linux/dma-direct.h b/include/linux/dma-direct.h
index 805010ea5346f91244bd4678a8dc0a61862166fc..2929685e88aa1e011abbf37307ffa9dcf23806cf 100644 (file)
--- a/include/linux/dma-direct.h
+++ b/include/linux/dma-direct.h
@@ -62,9 +62,6 @@ static inline bool dma_capable(struct device *dev, dma_addr_t addr, size_t size,
 {
        dma_addr_t end = addr + size - 1;
 
-       if (!dev->dma_mask)
-               return false;
-
        if (is_ram && !IS_ENABLED(CONFIG_ARCH_DMA_ADDR_T_64BIT) &&
            min(addr, end) < phys_to_dma(dev, PFN_PHYS(min_low_pfn)))
                return false;

diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index 848c95c27d79ff93394877a0132c075c7b094e8f..9a045e51df1776f6beb663e2983c0473930e7124 100644 (file)
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -144,6 +144,10 @@ dma_addr_t dma_map_page_attrs(struct device *dev, struct page *page,
        dma_addr_t addr;
 
        BUG_ON(!valid_dma_direction(dir));
+
+       if (WARN_ON_ONCE(!dev->dma_mask))
+               return DMA_MAPPING_ERROR;
+
        if (dma_map_direct(dev, ops))
                addr = dma_direct_map_page(dev, page, offset, size, dir, attrs);
        else
@@ -179,6 +183,10 @@ int dma_map_sg_attrs(struct device *dev, struct scatterlist *sg, int nents,
        int ents;
 
        BUG_ON(!valid_dma_direction(dir));
+
+       if (WARN_ON_ONCE(!dev->dma_mask))
+               return 0;
+
        if (dma_map_direct(dev, ops))
                ents = dma_direct_map_sg(dev, sg, nents, dir, attrs);
        else
@@ -213,6 +221,9 @@ dma_addr_t dma_map_resource(struct device *dev, phys_addr_t phys_addr,
 
        BUG_ON(!valid_dma_direction(dir));
 
+       if (WARN_ON_ONCE(!dev->dma_mask))
+               return DMA_MAPPING_ERROR;
+
        /* Don't allow RAM to be mapped */
        if (WARN_ON_ONCE(pfn_valid(PHYS_PFN(phys_addr))))
                return DMA_MAPPING_ERROR;