From: Jason Gunthorpe jgg@ziepe.ca
[ Upstream commit cb30dfa75d55eced379a42fd67bd5fb7ec38555e ]
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.
Link: https://patch.msgid.link/r/0-v1-663679b57226+172-iommufd_dirty_div0_jgg@nvid... Cc: stable@vger.kernel.org Fixes: 58ccf0190d19 ("vfio: Add an IOVA bitmap support") Reviewed-by: Joao Martins joao.m.martins@oracle.com Reviewed-by: Nicolin Chen nicolinc@nvidia.com Reviewed-by: Kevin Tian kevin.tian@intel.com 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 => drivers/vfio/iova_bitmap.c ] Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/vfio/iova_bitmap.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/drivers/vfio/iova_bitmap.c b/drivers/vfio/iova_bitmap.c index 38b51613ecca9..3f48125e2b9f0 100644 --- a/drivers/vfio/iova_bitmap.c +++ b/drivers/vfio/iova_bitmap.c @@ -127,9 +127,8 @@ 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); }
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