[PATCH v2] iommu: amd: Fix IO_PAGE_FAULT due to __unmap_single() size overflow

[PATCH v2] iommu: amd: Fix IO_PAGE_FAULT due to __unmap_single() size overflow

[Suravee Suthikulpanit]

Currently, an integer is used to specify the size in unmap_sg().
With 2GB worth of pages (512k 4k pages), it requires 31 bits
(i.e. (1 << 19) << 12), which overflows the integer, and ends up
unmapping more pages than intended. Subsequently, this results in
IO_PAGE_FAULT.

Uses size_t instead of int to pass parameter to __unmap_single().

Please note that this patch is only for the stable-kernels tree
because the commit be62dbf554c5 ("iommu/amd: Convert AMD iommu driver
to the dma-iommu api"), which removes the function unmap_sg()
was introduced in v5.5. This patch is not applicable in subsequent
kernel versions.

Cc: stable@vger.kernel.org
Cc: iommu@lists.linux-foundation.org
Reported-by: Robert Lippert <rlippert@google.com>
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
---

 drivers/iommu/amd_iommu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
index 32de8e7bb8b4..7adc021932b8 100644
--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -2670,7 +2670,7 @@ static void unmap_sg(struct device *dev, struct scatterlist *sglist,
 	struct protection_domain *domain;
 	struct dma_ops_domain *dma_dom;
 	unsigned long startaddr;
-	int npages;
+	size_t npages;
 
 	domain = get_domain(dev);
 	if (IS_ERR(domain))
-- 
2.17.1

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Re: [PATCH v2] iommu: amd: Fix IO_PAGE_FAULT due to __unmap_single() size overflow

[Greg KH]

On Wed, Jun 24, 2020 at 08:41:21AM +0000, Suravee Suthikulpanit wrote:
> Currently, an integer is used to specify the size in unmap_sg().
> With 2GB worth of pages (512k 4k pages), it requires 31 bits
> (i.e. (1 << 19) << 12), which overflows the integer, and ends up
> unmapping more pages than intended. Subsequently, this results in
> IO_PAGE_FAULT.
> 
> Uses size_t instead of int to pass parameter to __unmap_single().
> 
> Please note that this patch is only for the stable-kernels tree
> because the commit be62dbf554c5 ("iommu/amd: Convert AMD iommu driver
> to the dma-iommu api"), which removes the function unmap_sg()
> was introduced in v5.5. This patch is not applicable in subsequent
> kernel versions.

So what exact stable kernel version(s) do you want to see this patch
applied to?

thanks,

greg k-h
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Re: [PATCH v2] iommu: amd: Fix IO_PAGE_FAULT due to __unmap_single() size overflow

[Joerg Roedel]

On Wed, Jun 24, 2020 at 08:41:21AM +0000, Suravee Suthikulpanit wrote:
> Currently, an integer is used to specify the size in unmap_sg().
> With 2GB worth of pages (512k 4k pages), it requires 31 bits
> (i.e. (1 << 19) << 12), which overflows the integer, and ends up
> unmapping more pages than intended. Subsequently, this results in
> IO_PAGE_FAULT.
> 
> Uses size_t instead of int to pass parameter to __unmap_single().
> 
> Please note that this patch is only for the stable-kernels tree
> because the commit be62dbf554c5 ("iommu/amd: Convert AMD iommu driver
> to the dma-iommu api"), which removes the function unmap_sg()
> was introduced in v5.5. This patch is not applicable in subsequent
> kernel versions.
> 
> Cc: stable@vger.kernel.org
> Cc: iommu@lists.linux-foundation.org
> Reported-by: Robert Lippert <rlippert@google.com>
> Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>

Acked-by: Joerg Roedel <jroedel@suse.de>

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Re: [PATCH v2] iommu: amd: Fix IO_PAGE_FAULT due to __unmap_single() size overflow

[Joerg Roedel]

Hi Greg,

On Wed, Jun 24, 2020 at 11:09:06AM +0200, Greg KH wrote:
> So what exact stable kernel version(s) do you want to see this patch
> applied to?

It is needed in kernels <= v5.4. Linux v5.5 has replaced the code with
the bug.


	Joerg
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Re: [PATCH v2] iommu: amd: Fix IO_PAGE_FAULT due to __unmap_single() size overflow

[Greg KH]

On Wed, Jun 24, 2020 at 01:58:27PM +0200, Joerg Roedel wrote:
> Hi Greg,
> 
> On Wed, Jun 24, 2020 at 11:09:06AM +0200, Greg KH wrote:
> > So what exact stable kernel version(s) do you want to see this patch
> > applied to?
> 
> It is needed in kernels <= v5.4. Linux v5.5 has replaced the code with
> the bug.

This doesn't apply to any older kernels that I can see :(
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