Re: [PATCH] iommufd/selftest: Fix page-size check in iommufd_test_dirty()

[Jason Gunthorpe <jgg@nvidia.com>]

On Mon, Oct 30, 2023 at 11:34:46AM +0000, Joao Martins wrote:
> iommufd_test_dirty()/IOMMU_TEST_OP_DIRTY sets the dirty bits in the mock
> domain implementation that the userspace side validates against what it
> obtains via the UAPI.
> 
> However in introducing iommufd_test_dirty() it forgot to validate page_size
> being 0 leading to two possible divide-by-zero problems: one at the
> beginning when calculating @max and while calculating the IOVA in the
> XArray PFN tracking list.
> 
> While at it, validate the length to require non-zero value as well, as we
> can't be allocating a 0-sized bitmap.
> 
> Reported-by: syzbot+25dc7383c30ecdc83c38@syzkaller.appspotmail.com
> Closes: https://lore.kernel.org/linux-iommu/00000000000005f6aa0608b9220f@google.com/
> Fixes: a9af47e382a4 ("iommufd/selftest: Test IOMMU_HWPT_GET_DIRTY_BITMAP")
> Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
> ---
> This applies against iommufd for-next, but on the other hand it could also be
> squashed in the commit in the Fixes: tag. Both should apply cleanly.
> ---
>  drivers/iommu/iommufd/selftest.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)

Applied, thanks

Jason