* [PATCH rc] iommufd: Don't overflow during division for dirty tracking
@ 2025-10-08 18:17 Jason Gunthorpe
2025-10-08 18:57 ` Nicolin Chen
` (3 more replies)
0 siblings, 4 replies; 5+ messages in thread
From: Jason Gunthorpe @ 2025-10-08 18:17 UTC (permalink / raw)
To: iommu, Joerg Roedel, Kevin Tian, Robin Murphy, Will Deacon
Cc: Alex Williamson, Joao Martins, patches, stable,
syzbot+093a8a8b859472e6c257, Yishai Hadas
If pgshift is 63 then BITS_PER_TYPE(*bitmap->bitmap) * pgsize will overflow
to 0 and this triggers divide by 0.
In this case the index should just be 0, so reorganize things to divide
by shift and avoid hitting any overflows.
Cc: stable@vger.kernel.org
Fixes: 58ccf0190d19 ("vfio: Add an IOVA bitmap support")
Reported-by: syzbot+093a8a8b859472e6c257@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=093a8a8b859472e6c257
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
---
drivers/iommu/iommufd/iova_bitmap.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/drivers/iommu/iommufd/iova_bitmap.c b/drivers/iommu/iommufd/iova_bitmap.c
index 4514575818fc07..b5b67a9d3fb35e 100644
--- a/drivers/iommu/iommufd/iova_bitmap.c
+++ b/drivers/iommu/iommufd/iova_bitmap.c
@@ -130,9 +130,8 @@ struct iova_bitmap {
static unsigned long iova_bitmap_offset_to_index(struct iova_bitmap *bitmap,
unsigned long iova)
{
- unsigned long pgsize = 1UL << bitmap->mapped.pgshift;
-
- return iova / (BITS_PER_TYPE(*bitmap->bitmap) * pgsize);
+ return (iova >> bitmap->mapped.pgshift) /
+ BITS_PER_TYPE(*bitmap->bitmap);
}
/*
base-commit: 2a918911ed3d0841923525ed0fe707762ee78844
--
2.43.0
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH rc] iommufd: Don't overflow during division for dirty tracking
2025-10-08 18:17 [PATCH rc] iommufd: Don't overflow during division for dirty tracking Jason Gunthorpe
@ 2025-10-08 18:57 ` Nicolin Chen
2025-10-08 21:35 ` Joao Martins
` (2 subsequent siblings)
3 siblings, 0 replies; 5+ messages in thread
From: Nicolin Chen @ 2025-10-08 18:57 UTC (permalink / raw)
To: Jason Gunthorpe
Cc: iommu, Joerg Roedel, Kevin Tian, Robin Murphy, Will Deacon,
Alex Williamson, Joao Martins, patches, stable,
syzbot+093a8a8b859472e6c257, Yishai Hadas
On Wed, Oct 08, 2025 at 03:17:18PM -0300, Jason Gunthorpe wrote:
> If pgshift is 63 then BITS_PER_TYPE(*bitmap->bitmap) * pgsize will overflow
> to 0 and this triggers divide by 0.
>
> In this case the index should just be 0, so reorganize things to divide
> by shift and avoid hitting any overflows.
>
> Cc: stable@vger.kernel.org
> Fixes: 58ccf0190d19 ("vfio: Add an IOVA bitmap support")
> Reported-by: syzbot+093a8a8b859472e6c257@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=093a8a8b859472e6c257
> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Nicolin Chen <nicolinc@nvidia.com>
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH rc] iommufd: Don't overflow during division for dirty tracking
2025-10-08 18:17 [PATCH rc] iommufd: Don't overflow during division for dirty tracking Jason Gunthorpe
2025-10-08 18:57 ` Nicolin Chen
@ 2025-10-08 21:35 ` Joao Martins
2025-10-16 7:36 ` Tian, Kevin
2025-10-20 22:59 ` Jason Gunthorpe
3 siblings, 0 replies; 5+ messages in thread
From: Joao Martins @ 2025-10-08 21:35 UTC (permalink / raw)
To: Jason Gunthorpe
Cc: Alex Williamson, patches, stable, syzbot+093a8a8b859472e6c257,
Yishai Hadas, iommu, Joerg Roedel, Kevin Tian, Robin Murphy,
Will Deacon
On 08/10/2025 19:17, Jason Gunthorpe wrote:
> If pgshift is 63 then BITS_PER_TYPE(*bitmap->bitmap) * pgsize will overflow
> to 0 and this triggers divide by 0.
>
> In this case the index should just be 0, so reorganize things to divide
> by shift and avoid hitting any overflows.
>
> Cc: stable@vger.kernel.org
> Fixes: 58ccf0190d19 ("vfio: Add an IOVA bitmap support")
> Reported-by: syzbot+093a8a8b859472e6c257@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=093a8a8b859472e6c257
> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Joao Martins <joao.m.martins@oracle.com>
> ---
> drivers/iommu/iommufd/iova_bitmap.c | 5 ++---
> 1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/iommu/iommufd/iova_bitmap.c b/drivers/iommu/iommufd/iova_bitmap.c
> index 4514575818fc07..b5b67a9d3fb35e 100644
> --- a/drivers/iommu/iommufd/iova_bitmap.c
> +++ b/drivers/iommu/iommufd/iova_bitmap.c
> @@ -130,9 +130,8 @@ struct iova_bitmap {
> static unsigned long iova_bitmap_offset_to_index(struct iova_bitmap *bitmap,
> unsigned long iova)
> {
> - unsigned long pgsize = 1UL << bitmap->mapped.pgshift;
> -
> - return iova / (BITS_PER_TYPE(*bitmap->bitmap) * pgsize);
> + return (iova >> bitmap->mapped.pgshift) /
> + BITS_PER_TYPE(*bitmap->bitmap);
> }
>
> /*
>
> base-commit: 2a918911ed3d0841923525ed0fe707762ee78844
^ permalink raw reply [flat|nested] 5+ messages in thread
* RE: [PATCH rc] iommufd: Don't overflow during division for dirty tracking
2025-10-08 18:17 [PATCH rc] iommufd: Don't overflow during division for dirty tracking Jason Gunthorpe
2025-10-08 18:57 ` Nicolin Chen
2025-10-08 21:35 ` Joao Martins
@ 2025-10-16 7:36 ` Tian, Kevin
2025-10-20 22:59 ` Jason Gunthorpe
3 siblings, 0 replies; 5+ messages in thread
From: Tian, Kevin @ 2025-10-16 7:36 UTC (permalink / raw)
To: Jason Gunthorpe, iommu@lists.linux.dev, Joerg Roedel,
Robin Murphy, Will Deacon
Cc: Alex Williamson, Joao Martins, patches@lists.linux.dev,
stable@vger.kernel.org,
syzbot+093a8a8b859472e6c257@syzkaller.appspotmail.com,
Yishai Hadas
> From: Jason Gunthorpe <jgg@nvidia.com>
> Sent: Thursday, October 9, 2025 2:17 AM
>
> If pgshift is 63 then BITS_PER_TYPE(*bitmap->bitmap) * pgsize will overflow
> to 0 and this triggers divide by 0.
>
> In this case the index should just be 0, so reorganize things to divide
> by shift and avoid hitting any overflows.
>
> Cc: stable@vger.kernel.org
> Fixes: 58ccf0190d19 ("vfio: Add an IOVA bitmap support")
> Reported-by: syzbot+093a8a8b859472e6c257@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=093a8a8b859472e6c257
> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH rc] iommufd: Don't overflow during division for dirty tracking
2025-10-08 18:17 [PATCH rc] iommufd: Don't overflow during division for dirty tracking Jason Gunthorpe
` (2 preceding siblings ...)
2025-10-16 7:36 ` Tian, Kevin
@ 2025-10-20 22:59 ` Jason Gunthorpe
3 siblings, 0 replies; 5+ messages in thread
From: Jason Gunthorpe @ 2025-10-20 22:59 UTC (permalink / raw)
To: iommu, Joerg Roedel, Kevin Tian, Robin Murphy, Will Deacon
Cc: Alex Williamson, Joao Martins, patches, stable,
syzbot+093a8a8b859472e6c257, Yishai Hadas
On Wed, Oct 08, 2025 at 03:17:18PM -0300, Jason Gunthorpe wrote:
> If pgshift is 63 then BITS_PER_TYPE(*bitmap->bitmap) * pgsize will overflow
> to 0 and this triggers divide by 0.
>
> In this case the index should just be 0, so reorganize things to divide
> by shift and avoid hitting any overflows.
>
> Cc: stable@vger.kernel.org
> Fixes: 58ccf0190d19 ("vfio: Add an IOVA bitmap support")
> Reported-by: syzbot+093a8a8b859472e6c257@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=093a8a8b859472e6c257
> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
> ---
> drivers/iommu/iommufd/iova_bitmap.c | 5 ++---
> 1 file changed, 2 insertions(+), 3 deletions(-)
Applied to for-rc
Thanks,
Jason
^ permalink raw reply [flat|nested] 5+ messages in thread
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2025-10-08 18:17 [PATCH rc] iommufd: Don't overflow during division for dirty tracking Jason Gunthorpe
2025-10-08 18:57 ` Nicolin Chen
2025-10-08 21:35 ` Joao Martins
2025-10-16 7:36 ` Tian, Kevin
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