archive mirror
 help / color / mirror / Atom feed
From: Nicolas Saenz Julienne <>
To:,,, Christoph Hellwig <>,
	Marek Szyprowski <>,
	Robin Murphy <>
	Nicolas Saenz Julienne <>,
Subject: [PATCH v2 1/2] dma-direct: check for overflows on 32 bit DMA addresses
Date: Fri, 18 Oct 2019 13:00:43 +0200	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

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 <>
 include/linux/dma-direct.h | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/include/linux/dma-direct.h b/include/linux/dma-direct.h
index adf993a3bd58..af4bb9c81ccc 100644
--- a/include/linux/dma-direct.h
+++ b/include/linux/dma-direct.h
@@ -3,6 +3,7 @@
 #define _LINUX_DMA_DIRECT_H 1
 #include <linux/dma-mapping.h>
+#include <linux/memblock.h> /* for min_low_pfn */
 #include <linux/mem_encrypt.h>
@@ -27,6 +28,13 @@ static inline bool dma_capable(struct device *dev, dma_addr_t addr, size_t size)
 	if (!dev->dma_mask)
 		return false;
+	/* Check if DMA address overflowed */
+	if (min(addr, addr + size - 1) <
+		__phys_to_dma(dev, (phys_addr_t)(min_low_pfn << PAGE_SHIFT)))
+		return false;
 	return addr + size - 1 <=
 		min_not_zero(*dev->dma_mask, dev->bus_dma_mask);

  reply	other threads:[~2019-10-18 11:01 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-18 11:00 [PATCH v2 0/2] x86: Get rid of custom DMA functions Nicolas Saenz Julienne
2019-10-18 11:00 ` Nicolas Saenz Julienne [this message]
2019-10-30 21:41   ` [PATCH v2 1/2] dma-direct: check for overflows on 32 bit DMA addresses Christoph Hellwig
2019-10-31 10:44     ` Nicolas Saenz Julienne
2019-10-18 11:00 ` [PATCH v2 2/2] x86/PCI: sta2x11: use default DMA address translation Nicolas Saenz Julienne
2019-10-30 21:45   ` Christoph Hellwig
2019-10-31 10:43     ` Nicolas Saenz Julienne
2019-10-31 13:59     ` Alessandro Rubini

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \ \ \ \ \ \ \ \ \ \ \

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).