Re: [PATCH v2] iommufd/iova_bitmap: Fix shift-out-of-bounds in iova_bitmap_offset_to_index()

Jason Gunthorpe
2025-01-14T17:54:05Z

On Mon, Jan 13, 2025 at 10:38:20PM +0000, Qasim Ijaz wrote:
> Resolve a UBSAN shift-out-of-bounds issue in iova_bitmap_offset_to_index() where
> shifting the constant "1" (of type int) by bitmap->mapped.pgshift
> (an unsigned long value) could result in undefined behavior.
>
> The constant "1" defaults to a 32-bit "int", and when "pgshift" exceeds 31 (e.g., pgshift = 63)
> the shift operation overflows, as the result cannot be represented in a 32-bit type.
>
> To resolve this, the constant is updated to "1UL", promoting it to an unsigned long type
> to match the operand's type.
>
> Reported-by: syzbot <syzbot+85992ace37d5b7b51635@syzkaller.appspotmail.com>
> Closes: https://syzkaller.appspot.com/bug?extid=85992ace37d5b7b51635
> Fixes: 58ccf0190d19 ("vfio: Add an IOVA bitmap support")
> Signed-off-by: Qasim Ijaz <qasdev00@gmail.com>
> ---
> drivers/iommu/iommufd/iova_bitmap.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)

Applied to iommufd for-next

Thanks,
Jason