[PATCH 5.4 054/191] dma-direct: check for overflows on 32 bit DMA addresses

From: Greg Kroah-Hartman
Date: Thu Jan 02 2020 - 18:00:25 EST

From: Nicolas Saenz Julienne <nsaenzjulienne@xxxxxxx>

[ Upstream commit b12d66278dd627cbe1ea7c000aa4715aaf8830c8 ]

As seen on the new Raspberry Pi 4 and sta2x11's DMA implementation it is
possible for a device configured with 32 bit DMA addresses and a partial
DMA mapping located at the end of the address space to overflow. It
happens when a higher physical address, not DMAable, is translated to
it's DMA counterpart.

For example the Raspberry Pi 4, configurable up to 4 GB of memory, has
an interconnect capable of addressing the lower 1 GB of physical memory
with a DMA offset of 0xc0000000. It transpires that, any attempt to
translate physical addresses higher than the first GB will result in an
overflow which dma_capable() can't detect as it only checks for
addresses bigger then the maximum allowed DMA address.

Fix this by verifying in dma_capable() if the DMA address range provided
is at any point lower than the minimum possible DMA address on the bus.

Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@xxxxxxx>
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
include/linux/dma-direct.h | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/include/linux/dma-direct.h b/include/linux/dma-direct.h
index adf993a3bd58..6a18a97b76a8 100644
--- a/include/linux/dma-direct.h
+++ b/include/linux/dma-direct.h
@@ -3,8 +3,11 @@

#include <linux/dma-mapping.h>
+#include <linux/memblock.h> /* for min_low_pfn */
#include <linux/mem_encrypt.h>

+static inline dma_addr_t phys_to_dma(struct device *dev, phys_addr_t paddr);
#include <asm/dma-direct.h>
@@ -24,11 +27,16 @@ static inline phys_addr_t __dma_to_phys(struct device *dev, dma_addr_t dev_addr)

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;

- return addr + size - 1 <=
- min_not_zero(*dev->dma_mask, dev->bus_dma_mask);
+ min(addr, end) < phys_to_dma(dev, PFN_PHYS(min_low_pfn)))
+ return false;
+ return end <= min_not_zero(*dev->dma_mask, dev->bus_dma_mask);