CVE-2025-40293

In the Linux kernel, the following vulnerability has been resolved:

iommufd: Don’t overflow during division for dirty tracking

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.

More information : https://git.kernel.org/stable/c/07105e61882ff4a7d58db63cc5f9e90c6c60506c